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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 406
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 407
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 419
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 422
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 425
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 426
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 427
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 430
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 435
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 436
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 437
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 438
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 439
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 440
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 441
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 442
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 449
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 450
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 451
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 452
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 453
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 454
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 455
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 456
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 457
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 458
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 459
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 460
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 461
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 462
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 463
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 464
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Page 465
Suggested Citation:"THE ROLE OF INFORMATION PROCESSING IN PERCEPTUAL AND READING DISABILITIES." National Research Council. 1970. Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited. Washington, DC: The National Academies Press. doi: 10.17226/18684.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

THOMAS T. S. INGRAM The Nature of Dyslexia In this paper, I shall attempt to describe what has been and is meant by the terms "dyslexia," "specific dyslexia," and "developmental dyslexia"; these are common terms that have become confusing because authors have used them in so many different ways. I shall discuss a number of clinical syndromes involving serious difficulties experienced by appar- ently healthy children of average intelligence in learning to read and write. Some relevant work concerned with difficulties in learning to read and write carried out in the Department of Child Life and Health in the University of Edinburgh will be described. Reading and spelling disabilities acquired as a result of disease of the brain occurring when reading and writing skills have been developed will not be discussed. HISTORICAL REVIEW Many differences of opinion about reading disability in children have their origin in the ideas of earlier authors and in misconceptions about their work.21 At the risk of reviewing much literature that has already been discussed extensively, it seems worthwhile to describe the ways 405

THOMAS T. S. INGRAM in which specific difficulties in learning to read and spell came to be recognized. In the process, many terms were used without agreement on their definitions. The Recognition of "Word Blindness" In the last half of the nineteenth century, neurologists were particu- larly concerned with allocating specific psychologic functions to spe- cific areas of the brain. The identification of a "speech center" by Broca14 was followed by efforts to define parts of the brain that were particularly concerned with reading and writing. Descriptions of adult patients who lost the power to read and write as a result of a variety of brain lesions were soon published.4's'7'13'84 Henschen57 attributed word blindness, usually accompanied by difficulty in writing, to a lesion of the left angular gyrus. Dejerine30 considered that the lesion responsible for "alexia" was in the medial and inferior portions of the left occipital lobe.12-21 At the same time as the first papers on "congenital word deafness" and "developmental aphasia" or "congenital aphasia" were being writ- ten, the first inadequate accounts of children who were unable to rec- ognize written words or letters appeared. They were considered to suffer from "congenital word blindness."78'100 Soon, further reports described otherwise healthy children of apparently average intelligence who were "word blind" or "letter blind." Most of the early reports were by ophthalmologists.48'64'66'122'126 It was perhaps inevitable that, just as children who suffered from "congenital aphasia" were assumed to have brain lesions similar to those found in adults suffering from aphasia, so children with "congenital word blindness" or "congenital alexia" were suspected of having lesions similar to those described in adults who had lost the power to read and write. Fisher,49 for example, suggested that congenital aplasia of one or both angular gyri might be responsible for "congenital word-blindness." It was difficult, however, to reconcile that interpretation with reports of quite large numbers of familial cases of "word-blindness" that soon appeared.48'117'122'126'131 A family in which six cases occurred in two generations, including four in one sibship of 11 children, was described by Hinshelwood in 1917.65 As Critchley remarks,21 "what might be called the early history of this condition [developmental dyslexia] was closed by 1917, when Hinshelwood brought out his second monograph entitled Congenital 406

The Nature of Dyslexia Word-Blindness" (in which he reviewed his experience with 31 cases of congenital word blindness and summarized the work of other authors up to that time). Hinshelwood defined the condition as a congenital defect occurring in children with otherwise normal and undamaged brains, characterized by a disability in learning to read so great that it is manifestly due to a pathological condition and where the attempts to teach the child by ordinary methods have completely failed. Congenital word blindness occurred more commonly in boys than in girls and was often hereditary. Some children had difficulties in identi- fying whole words but could identify letters; others had difficulties in identifying individual letters. Some, but not all, could not recognize written figures. Hinshelwood considered that the disorder was the re- sult of a failure to develop the brain centers concerned with the visual memory of words, letters, or figures. Auditory memory was commonly unaffected. He made the acute observation that some children could read text if they were allowed to read aloud or even move their lips silently while reading, but could not read silently without movement of lips, tongue, or palate. Most patients could copy written material, but they were quite unable to write to dictation. Hinshelwood inter- preted this as indicating that there was a deficiency in the ability to remember letter and word shapes. Because of their difficulties in read- ing, many children guessed at words that they could not identify and used accompanying pictures as clues to the contents of the written ma- terial. He noted that many patients who suffered from "congenital word blindness" improved as they grew older and responded to teaching. Hinshelwood's account of the clinical findings in children who suf- fered from "congenital word blindness" was remarkably complete, al- though he did not comment on the frequent history of associated re- tarded speech development or on "crossed laterality," an increased tendency to left-handed ness and ambidexterity already noted by other authors.93-95 McCready postulated that there were common etiologic factors in "word-blindness," "congenital word-deafness," "delay in the acquisition of speech," and "stuttering." All these disorders could be regarded as being the result of "biological variations in the higher cere- bral centres causing retardation" of the various functions of language. He thought that they were the result of variations in the degree of cere- bral dominance that was also manifest in weakness of lateralization of 407

THOMAS T. S. INGRAM handedness shown by many patients. Hinshelwood's idea that under- development of cerebral dominance was important in determining the disturbance of spoken and written language in his patients probably had a considerable influence on later authors, particularly Orton.103'106 Study of Perceptual Defects After Hinshelwood's work, further studies of patients with difficulties in learning to read and spell were devoted largely to more accurate de- scriptions and analyses of their difficulties in recognizing, orienting, interpreting, and reproducing written symbols of spoken language. Bronner,15 in The Psychology of Special Abilities and Disabilities, appears to have been the first author to study systematically the na- ture of the perceptual defects associated with reading disability. She attributed reading disability to faulty visual memory in one child and to poor auditory discrimination and memory in another, but in many other patients she was unable to discover any evidence of perceptual deficits and was at a loss to account for the children's difficulties in learning to read. She speculated as to whether reading required some specific synthesizing ability that it was not possible to study with the means at her disposal. Fildes47 observed that children who failed to learn to read and write had difficulties in recognizing and reproducing shapes, designs, and patterns other than those found in written material. Unfortunately, a high proportion of her patients were mentally defec- tive; her findings may have been due partly to the fact that the discrim- inatory powers of her subjects were immature at the time of testing.62'63 Gates52 found that children aged 8 or more with reading disability were as able to detect small differences in the shapes of test objects as were those who had no reading difficulties. He denied that visual perception or memory could account for reading disability and thought unfavorable environmental factors—including defective teaching, poor home back- ground, and emotional disturbances—were more important than percep- tual difficulties in causing reading disability. Bachmann,3 using tachisto- scopic exposure techniques, came to similar conclusions. He was particularly impressed by the fact that children with specific reading difficulty read extremely slowly. Ombredane102 found no abnormal- ities of visual form discrimination in three carefully studied children aged 12-14 who had reading difficulty. The contemporary studies of Feyeux46 have not received the atten- 408

The Nature of Dyslexia tion they deserve. Not only did she describe accurately the findings in children with retardation of speech, but she also noted how frequently it was associated with difficulties in learning to read and write. She em- phasized that reading and writing difficulties must be considered to be parts of a general language disability, although she recognized that a proportion of children with difficulties in learning to read and spell showed no obvious abnormalities in the development of speech. Reversals Recognized Orton103'106 emphasized the extent to which children who suffered from "word blindness" tended to reverse the order of letters and syl- lables in words or of words in sentences. He noted the instability in recognizing and recalling the orientation of letters and the order of letters in words, which he called "strephosymbolia" (twisted symbols). In writing, this was manifest by the fact that letters were often mal- formed, apparently because the child was vague about the shape he was trying to reproduce. They were often reversed wholly or in part, and the order of letters, syllables, or words was often reversed or otherwise confused. Thus, spelling was very unreliable and inaccurate. Many pa- tients could write and read mirrorwise much more easily than unaf- fected children. Orton105 was impressed by the frequency with which he found his patients to be ambidextrous or left-handed or to show conflicting laterality of eye and hand. He hypothesized that in his patients there was an intermixture of control in the areas in the two hemispheres of the brain that serve the visual or reading part of the language function and that in normal children are active only in the dominant hemisphere. He suggested that there might be conflict between the mirror images in the two hemispheres when word-blind children attempt to build associ- ations between letters and spoken words. As a result, confusion of ori- entation and sequencing might occur: the data we have assembled from the study of left handedness and of various language difficulties in the family stock of children who have a specific disability in learning to read and show the strephosymbolia syndrome give what to me is convincing evidence that such children represent intergrades between right-sided and left-sided familial tendencies and that the reading disability follows fairly definite hereditary trends. ... In families with this disturbance there are also more than the expected number of left-handed members and persons with delayed 409

THOMAS T. S. INGRAM speech, stuttering, reading, writing and spelling disabilities, and abnormal clumsi- ness (developmental apraxia). In the childhood histories of children who come to attention as presenting reading and spelling problems we not infrequently find indi- cations of developmental deviations in their acquisition of speech and motor patterns. He was careful to point out that, although he had described "develop- mental word deafness," "developmental motor aphasia," "develop- mental alexia," and "developmental agraphia" separately, these dis- orders were in fact commonly found together in individual patients. He emphasized their common etiologic and clinical features and re- garded them as manifestations of a disorder of language as an evolutionary human function associated with the development of a hierarchy of complex integrations in the nervous system and culminating in uni- lateral control by one of the two brain hemispheres (cerebral dominance). Retardation in acquiring reading suggested that there was some inter- ference with this natural process of growth and development.104 Orton and his disciples stimulated interest in children who were slow to read. Many papers appeared in the United States and in European countries describing patients who were "dyslexic," "alexic," or "re- tarded readers" suffering from "strephosymbolia." Many of these papers20'88 reported children with symptom complexes very similar to those described by Orton. Creak20 described 38 boys and 12 girls with intelligence quotients upwards of 70 who attended a child psychiatric clinic. They were 2 years retarded in reading, compared with their mental ages as judged by standard tests. She noted that, compared with children in the normal population, a high proportion of patients showed mixed dominance, i.e., were left-handed and right-eyed or right-handed and left-eyed. She asked children to match shapes and patterns and reproduce them from memory and with the pattern in front of them. She tested their ability to listen to a simple rhythm and to reproduce it; many of her patients failed to do it. She found that reversals of numbers in reading and writing to dictation occurred less frequently than she had expected on the basis of the findings of Orton103 and Monroe." She noted the frequency with which psychiatric symptoms were found in children suffering from reading disabilities and speculated about the extent to which these symptoms were the result of reading difficulties and con- 410

The Nature of Dyslexia sequent unhealthy attitudes on the parts of parents and teachers and about the extent to which they contributed to educational failure. Un- fortunately, a rather high proportion of her patients were of below average intelligence. Eustis42 described a family in which four generations showed an excess of ambidexterity, left-handedness, body clumsiness, retarded speech development, or other speech disorders and reading disability. He noted that "these conditions occur together in the individual and in his family tree sufficiently often to constitute a syndrome," but that all the symptoms he had described were found normally in infants and young children, and were to be regarded as abnormal only when they persisted into later childhood and adult life. Eustis41 described 23 children with reading disability in 21 families. He found a family his- tory of speech or reading difficulty in a high proportion of patients. The massive work of Hallgren55 in Stockholm contributed significantly to the understanding of the genetics of "specific dyslexia." Hallgren found that 88% of the children he studied had a family history of speech or reading disorders. In a series of studies, Hermann and his colleagues59-61 reported on the deficient penmanship and abnormal spelling of children with "spe- cific dyslexia." In writing, there was malalignment of letters, omission or repetition of words and letters, rotation of letters, odd punctuation marks, and misspellings. Typical faults were the partial or complete re- versal of groups of letters and too short or too long linkages between letters. Sometimes letters ran into each other and children were espe- cially likely to omit letters that were not sounded. He noted the marked tendency for children to write "phonetically" and related it to their poor memory for the shapes of words. He suggested that that might be attributed to some "underlying idiomotor apraxia." Hermann59"61 considered that children with specific dyslexia could be defined as those having a defective capacity for acquiring at the normal time a proficiency in reading and writing corresponding to average performance; the deficiency is dependent upon constitutional factors (heredity), is often accompanied by difficulties with other symbols (numbers, musical notation, etc.), it exists in the absence of intellectual defect or defects of the sense organs which might retard the normal accomplish- ment of these skills, and in the absence of past or present appreciable inhibitory influences in the internal and external environments. 411

THOMAS T. S. INGRAM Hermann was struck by the similarity of the findings in children with "word-blindness" and those in Gerstmann's syndrome, in which right- left confusion, finger agnosia, dyscalculia, and agraphia were found. He wrote58: After having had the opportunity of examining a number of patients with Gerstmann's syndrome and having perused more than 1,000 case histories at the Ordblindeinstituttet, Copenhagen, I have no doubt that the fundamental disturbance in congenital word-blindness is the same as that of Gerstmann's syndrome. Further case reports were made by Rabinovitch and co-workers112'113; Bender6 and de Hirsch28 noted that the "verbal visual configurations" of children suffering from specific dyslexia tended to remain unstable; "perceptual, visuo-motor and motor patterning often remains inferior. Their auditory discrimination is often poor, their Bender Gestalt is relatively primitive." Relationship with Speech Development Ingram and Reid75 attempted to distinguish healthy, intelligent chil- dren from good environments with developmental dyslexia according to their performance on the Wechsler Verbal and Performance Scales. It was found that children whose scores on the Performance Scales were significantly inferior to those on the Verbal Scale more often showed errors of visuospatial type when reading and spelling, whereas those whose scores on the Verbal Scale were inferior more often had difficulties of audiophonic type. Some patients with a history of re- tarded speech development and poor performance on the Wechsler Verbal Scale had both visuospatial and audiophonic difficulties and were thus severely educationally handicapped. As in other similar sur- veys, a high proportion of patients had a positive family history of re- tarded speech development, stammer, and educational difficulties. Only 29% of patients were considered to have strong lateralization of handedness, and 52% were left-eyed. It will be seen that many of the findings in this study are similar to those reported by Creak.20 Some further evidence that patients with retarded speech develop- ment may have associated defects of visuospatial perception is found in the work of Doehring.32 Doehring studied 20 children with severely re- tarded speech development who were diagnosed as "aphasic" and com- 412

The Nature of Dyslexia pared their ability to memorize the localization of a visual stimulus. He found that the accuracy of the performance of the aphasic group was significantly less than that of a matched group of deaf children or that of a group of normal children. He concluded that "children classified as aphasic are retarded in some, but not all, aspects of visual percep- tual ability." Kinsbourne and Warrington79'81'83 took this work further. They developed a test of finger differentiation and demonstrated that 95% of children over the age of 7 years succeeded in identifying their fingers in the tests that had been developed. They postulated that children who showed relative inferiority of scores on the Wechsler Performance Scales, compared with the Verbal Scale, might show dif- ficulties in finger differentiation more frequently than those with rela- tively inferior performance on the Verbal Scale. In particular, they thought that there might be an association between inability to rec- ognize one's fingers and inability to succeed in subtests of the Wechsler Intelligence Scale for Children (wise) with a high spatial loading.92 They concluded that the differentiation of patients according to Ingram and Reid's criteria was valid and wrote80: It appears that among backward readers and writers there exist two groups with developmental defects reminiscent of acquired cerebral syndromes in adults. Group 1 will be called the language retardation group and Group 2 the Gerstmann group. The two groups are readily distinguishable by use of the finger tests. The Gerst- mann group is further characterized by a positive discrepancy score on the wise greater than that occurring naturally in 95 per cent of the population. They considered that in Group 1 there were difficulties in the sphere of language, whereas in Group 2 poor progress in learning to read and write was attributable to difficulties in sequential ordering. In further studies of the nature of the difficulties in the two groups of patients they had defined, they noted that children with retarded language development had a high proportion of extraneous letters in their writing to dictation, whereas patients with difficulties in finger differentiation produced a high proportion of errors related to letter order. They concluded that patients with a history of retarded speech development misspelled words in different ways and for different rea- sons than did those who had higher scores on the Wechsler Verbal Scale than on the Wechsler Performance Scales and associated difficulties in differentiating fingers. They considered that 413

THOMAS T. S. INGRAM the association between finger agnosia and order errors in spelling appears to reflect an underlying, more general difficulty in processing information, both verbal and nonverbal, in terms of spatiotemporal sequence.83 Kinsbourne and Warrington,83 like Ingram and Reid,75 emphasized that there appeared to be a number of different clinical syndromes that re- sulted in reading and spelling backwardness of greater or lesser specificity. Lateralization Zangwill137"139 discussed the significance of weak lateralization of handedness in dyslexia. He was skeptical of studies that merely com- pared the incidence of atypical laterality in matched groups of back- ward and normal readers, because he considered that reading retarda- tion could have many different causes. He felt that it would be useful to ask whether there were particular types of reading backwardness associated with anomalies of laterality. He thought it likely that such differences would be found, and he wrote139: I have been struck by the frequency of retarded speech development, defects of spatial perception, motor clumsiness, and related indications of defective matura- tion in cases of dyslexia presenting in ill-lateralised (and some left handed) chil- dren.138 In dyslexia presenting in fully right handed children (without familial sinistrality), on the other hand, I have been more impressed by the comparative "purity" of the disorder. It is in these latter cases, perhaps, that a specific genetical factor, as adduced by Hallgren55 and Hermann,59 might plausibly be assumed. He considered that "minimal brain injury at birth" and "familial dyslexia" need not be mutually exclusive and that individuals lacking strong and consistent lateral preference might be particularly vulnerable to the effects of stress—"for instance, minimal brain injury at birth may affect more severely those who show no strong tendency to lateral specialization."139 Most authors report that significantly more boys than girls suffer from serious difficulties in learning to read and write. The male: female ratio is between 3:1 and 5:1 in most large series.21 But in almost every other respect, there are major inconsistencies in the findings of authors who describe different series of patients suffering from specific dyslexia. 414

The Nature of Dyslexia These are largely attributable to the different ages at which patients were studied and the very different means of selection. For example, Hallgren's patients came largely from remedial classes for children with retarded reading ability.55 Patients described by Betts,8 Eames,37-39 and Park107 were reported to have a high incidence of ophthalmologic abnormalities, but this may not be surprising in view of the fact that the authors were particularly interested in disorders of vision and visual per- ception. Most studies have shown that minor defects of acuity, visual fusion, and strabismus are not major causes of the types of reading dis- abilities that have been described. Abnormalities of eye movement dur- ing reading are almost certainly secondary to an underlying difficulty in visuospatial orientation, rather than primary causes.21'55 A high inci- dence of emotional disturbances among patients referred to departments of child psychiatry is inevitable.20'75'111 Drew,35 a neurologist, found minor neurologic abnormalities in a father and his two sons who suf- fered from "familial congenital word-blindness," and suggested that minor neurologic abnormalities might have been found more commonly in more patients if they had been looked for—especially, perhaps, in series described by pediatricians. NEW STUDIES In a recent retrospective study, 176 children aged 7 or over were referred to the Department of Child Life and Health, Edinburgh, on account of suspected "dyslexia." They were referred from family doc- tors, school medical officers, and psychologists, and the majority had been examined in the Neurological and Speech Clinics of the Royal Hospital for Sick Children, Edinburgh; thus, they were highly pre- selected. Fifty-four were excluded from further consideration because they were found not to be failing in reading, and the apparent educa- tional difficulties of another 19 were considered to be explicable on grounds of their being of below average intelligence or because of inter- rupted schooling or other environmental factors. Inadequate motivation and sensory defects appeared to explain the backwardness of nine chil- dren; eight failed to complete the testing and were excluded from the series; and four were too old for reliable diagnosis. There remained 82 patients who were considered to show reading failure as assessed by their scores on the Schonell Graded Word Test and the Stanford-Binet 415

THOMAS T. S. INGRAM Intelligence Scale 1960 Revision (Form L-M). Patients were considered to be mildly affected if there was a discrepancy of 10-14 points between their reading quotients and their intelligence quotients, moderately af- fected if there was a discrepancy of 15-29 points, and severely affected if there was a discrepancy of 30 or more points. As a group, these children were reading at an average of more than 2 years below their chronologic age. Only three children were reading at the level of their chronologic age, but they were more than 3 years re- tarded in reading ability, commensurate with their mental age. An attempt was made to classify children by the likelihood of their suffering from "brain damage" according to their histories and indica- tions of brain dysfunction ascertained in the course of detailed neuro- logic examination and electroencephalography. Birth histories were judged arbitrarily in the same way as were those of patients suffering from cerebral palsy in a previous study.71 They were scored for the possible and probable traumatic, hypoxic, and toxic insults that they might have suffered in utero. Thus, mild or moderately severe pre- eclampsia was scored as one hypoxic insult, severe pre-eclampsia or antepartum hemorrhage or prolapse of the cord as two hypoxic insults. Midcavity forceps delivery was counted as one traumatic insult, but la- bor prolonged beyond 36 hr in a first gestation or beyond 24 hr in a second gestation, breech extraction, and high forceps delivery were counted as two traumatic insults each. Apnea up to 5 min was consid- ered as one hypoxic insult, more prolonged apnea or cyanosis for more than an hour as two hypoxic insults. Patients who were born after un- complicated pregnancies, labors, and deliveries and who were normal in the neonatal period were placed in category 0, those with one or two insults in category 1, those with three or four insults in category 2, and those with five or more insults in category 3. A history of "clumsiness" or delayed motor milestones sufficiently severe to make the parents seek medical advice placed a patient in cate- gory 1. A history of convulsions with fever, strabismus, or other condi- tions frequently associated with chronic brain disease placed a patient in category 2. A history of definite head injury, meningitis, or encepha- litis or of persistent neurologic impairment, such as ataxia or neglect of a hand, placed a patient in category 3. Patients were also classified according to the findings of neurologic examination. Patients without abnormal neurologic signs were placed 416

The Nature of Dyslexia in category 0. Those with minimal incoordination or a mild excess of contralateral associated movement, for example on the Fog test, were placed in category 1; they probably had no more than a degree of neu- rologic immaturity.51 In category 2 were those with more evidence of motor impairment, particularly those showing the choreoid syndrome or mild asymmetries in the reflexes without definite paresis. Patients with definite cerebral palsy or with epilepsy were placed in category 3. The electroencephalograms of patients were also classified into four categories. Normal records for age were in category 0; records that showed a mild excess of slow activity or minor asymmetries but no paroxysmal activity were in category 1; records in which there was a definite excess of slow activity that might be paroxysmal were in cate- gory 2; and records with focal spike activity, spike wave activity, or other evidence of epilepsy were in category 3. In assessing the likelihood of underlying brain damage, most weight was given to the results of neurologic examination, for that seemed to be the most informative method of study and did not rely on retro- spective findings.74 As stated, all patients were given the Stanford-Binet Intelligence Scale 1960 Revision (Form L-M). All but six, for whom reports from the school authorities were accepted, were given standardized tests in mechanical arithmetic (Schonell Form A or B), and the Schonell Spell- ing Test (S 1) was administered. The Goodenough Draw A Man Test was given to 49 children under the age of 10 years. Children were placed in one of two categories according to the results of these tests. In the first category were 62 children who appeared to have specific reading and spelling difficulty only (referred to for the sake of brevity as "specifics"). In the second were 20 children who failed in reading, spelling, and arithmetic (referred to as "generals" because they had gen- eral learning difficulty in spite of favorable mental, emotional, and en- vironmental factors). The "specifics" and "generals" were similar in age, social class, and average IQ. The composition of the subgroups differed appreciably only in the sex ratio, the "generals" showing a higher proportion of girls than the "specifics." More than 50% of patients gave a history of slow speech development, the percentage being similar in the two groups. About 40% of the "specifics" and 25% of the "generals" had a family history of reading and spelling difficulties in sibs, parents, or aunts and 417

THOMAS T. S. INGRAM uncles; 66% of those with a positive family history of reading difficul- ties were in the category of severe reading failures. All the "generals" with positive family histories were boys, and all were severe reading failures. In a slightly comparable group of 30 children of equivalent intelligence and social class (but not comparable in other respects), who read normally, a family history of reading difficulty was found in only 9%. The "specifics" had less evidence of brain damage or dysfunction than the "generals," whether this was assessed on the basis of birth and developmental history, clinical examination, or electroencephalography. Thus, 68% of the "specifics" and only 35% of the "generals" were con- sidered to have no significant neurologic abnormalities; 22% of the "specifics" and 60% of the "generals" had significant neurologic ab- normalities. About 66% of the "specifics" had normal electroencephal- ograms, compared with only 16% of the "generals." These are differ- ences of statistical significance. An attempt was made to classify the types of reading error made by patients in the two groups. Difficulties in learning to recognize written symbols, associate them with the corresponding auditory image, and then synthesize them into words are characteristic of the early stage of reading. At a later stage, visual recognition of words becomes immedi- ate, and finally the child reads by making a series of hypotheses, often on slight contextual clues, and learns to "scan" a line of print or script.87'134 All the "specifics" made errors characteristic of the early stage of reading, involving confusion of letters or audiophonic synthesis. These were found less frequently in the "generals." Although 77% of all "spe- cifics" made audiophonic mistakes, only 10% of the "generals" did. In 11% of the "specifics" only audiophonic mistakes were made, whereas none of the "generals" made only that primitive type of error. Audio- phonic difficulties of this type were very striking in patients in the "specific" group who had a history of retarded speech development, but they were not the only cause of their reading failure. For example, one 8-year-old in the "specific" group who had undergone entirely normal development, had normal neurologic findings, and was of very superior intelligence could not recognize the simplest words in print— such as "dog," "man," or "my." In such cases, some inadequacy of visual recognition must be postulated. Although evidence of brain damage was usually, but not exclusively, associated with dyslexia and additional educational difficulties, it was 418

The Nature of Dyslexia not associated with a greater degree of difficulty in learning to read: 70% of the "generals" who had no evidence of brain abnormalities showed severe reading failure, but only 57% of those with definite evi- dence of brain abnormality showed severe reading failure. Furthermore, among the "specifics," 60% of those with normal neurologic findings had severe reading failure, compared with only 33% of those with defi- nite evidence of brain disease. It is impossible to place the patients described in clearly defined categories on the basis of the findings reported. It is evident, however, that specific reading handicaps may be present in association with no clinical or electroencephalographic indications of brain abnormality, with definite clinical indications of brain abnormality, or with neuro- logic signs that are more suggestive of neurologic immaturity than of serious focal disease. When there are definite clinical signs of brain abnormality, general educational difficulties are more likely to be found than isolated read- ing retardation, and the family history is less often positive for reading and spelling disorders. Even in the group of patients with specific reading disability without clinical evidence of brain disease and with a positive family history of reading and writing difficulties, it is possible to discern different groups— for example, those whose errors in reading and spelling are predomi- nantly visuospatial and those whose errors are predominantly of the audiophonic type, with the latter more often having a history of re- tarded speech development.74 This survey, being retrospective and dealing with a highly selected population, is not very different from a number of others that have been described previously in this paper, but the findings do indicate that "specific developmental dyslexia" should not be regarded as a single disease entity. Moreover, it suggests, in agreement with Zangwill, that "hereditary dyslexia" and "dyslexia due to brain injury" are not necessarily mutually exclusive categories.139 It is apparent that there is a need for detailed studies of carefully selected groups of children with reading difficulties from the neuro- logic, ophthalmologic, psychologic, and psychiatric points of view, so that the various syndromes associated with more or less "specific dys- lexia" or "specific developmental dyslexia" may be further defined.98 At the same time, it is only through comprehensive surveys of repre- sentative groups of schoolchildren that the relative importance of these syndromes in causing retardation can be assessed. 419

THOMAS T. S. INGRAM POPULA TION SUR VEYS While clinicians were publishing large numbers of case reports about children considered to suffer from specific dyslexia, psychologists and educationalists were attempting to estimate the size and nature of the problem of reading backwardness in large school popula- tions.16'99'120'121'129 Monroe,99 reporting as a former research associ- ate of Orton, found 15 possible "causative factors" in reading disabil- ity. She recognized two major types of disability: "a lack of precision in discrimination of complex visual patterns," shown in the child's reading by his inability to comprehend words as units, although he might be able to recognize them when they were spelled out to him; and "a lack of precision in discrimination of spatial orientation," similar to the tendency to reverse symbols and the order of written symbols described by Orton103 as "strephosymbolia." MacMeeken88 studied 383 children in a large Edinburgh primary school between the ages of 7 years 6 months and 10 years 5 months. In her words, "a cross section would show that the children come from homes fairly far down but not very far up the social scale." MacMeeken gave individual tests of intelligence and reading ability. She obtained a reading-accomplishment quotient by using the for- mula, (reading age/mental age) X 100, and considered that those with quotients of less than 85 were suffering from reading disability and those with quotients of between 85 and 90 were "handicapped." Of the children she tested, 9.1% had quotients of 85 or less: 12.2% of the boys and 6.2% of the girls, a difference that was almost statistically sig- nificant. The mean intelligence quotients of children with reading dis- ability were 106.3 for boys (range, 83-137) and 101.9 for girls (range, 86-121). A very high proportion showed left-eye dominance, although the distribution by handedness was not different from that of children in the general population. MacMeeken recognized that "absences, changes of school, defective eye sight, defective hearing may and do produce reading achievement which is low in relation to mental ca- pacity," but she considered these causes insufficient in themselves to produce disability of the severe degree that she found, although they might be contributory causes. She considered that these children are developmental aphasics showing in varying degree and as major aspects of their pattern of difficulty the two aphasic syndromes of word recognition 420

The Nature of Dyslexia difficulty and the strephosymbolic tendency to reverse letters, to distort letters or syllables within words. Her findings may be compared with those obtained in a survey of primary-school children in Stockholm carried out by Hallgren,55 whose conclusions were broadly similar, although he found a lower incidence of "left-eye dominance." In a study of children in England, the Ministry of Education97 found that 1 % of 18-year-olds, 1.4% of 15-year-olds, and 4.2% of 11-year-olds had reading ages of less than 7 years. Some 3 years later, a survey96 was carried out in Middlesborough after programs of remedial reading had been established. A somewhat smaller proportion of the population of 11-year-olds had reading ages of less than 7 years: 3.9% of boys and 1.3% of girls. In Leeds, 19% of 1985 11-and 12-year-olds, excluding those who attended grammar (i.e., public) schools, were more than 2 years retarded in reading, as judged by chronologic age, and 8.6% were 2 years retarded, as judged by mental age.19 More recently, Morris101 noted that 19.2% of 7-year-olds in Kent County, England, were still using their first reader, which implied that they had hardly begun to learn to read. A nationwide study77 of 11,000 British 7-year-olds found that 11.2% of boys and 5.9% of girls had not progressed beyond their first reading boojc after 2 years of elementary-school instruction. The difference in the proportions of boys and girls with reading retardation was statisti- cally significant. In the United States, Eisenberg40 studied the reading proficiency of the entire sixth-grade population (aged about 12 years) in a large urban center. Some 28% were found to be two or more grades below their ex- pected level, whereas in "commuter county," 15% were two or more grades below expected level, and in superior independent schools, 0% (Table 1). In the independent schools, 82% were two or more grades in advance of their expected reading ability. Eisenberg, like the authors of the other population studies quoted, emphasized the multiplicity of fac- tors that could produce reading disability—sociopsychologic: quantita- tive and qualitative defects in teaching, deficiencies in cognitive stimu- lation, and deficiencies in motivation (associated with social pathology or with psychopathology); and psychophysiologic: general debility, sensory defects, intellectual defects, brain injury, and specific (idio- pathic) reading disability. 421

THOMAS T. S. INGRAM TABLE 1 Reading Levels of Sixth-Grade Children by School System" % Retarded School System Test > 1 Grades > 1 Grade % Advanced ^ 2 Grades Metropolis Stanford 28 57 9 Commuter county California IS 35 8 Suburbia Iowa 3 19 34 Independent Stanford 0 1 82 aDerived from Eisenberg. British workers have similarly been reluctant to subscribe to the view that specific developmental dyslexia is a major cause of reading disabil- ity. Burt16 refuted the idea that specific dyslexia was of major impor- tance, and Vernon127 wrote that "investigations which have been cited give no clear evidence as to the existence of any innate organic condi- tion which causes reading disability except perhaps in a minority of cases; though certainly innate factors may predispose the child toward difficulty in learning to read." She appears to have regarded specific dyslexia as an irremediable condition, and many of the studies she quotes describe patients who probably would have been diagnosed by many clinicians and psychologists as suffering from "specific dyslexia." Nevertheless, she admits that "there may be a class of individuals who are generally lacking in maturation, these are the cases . . . who have no well established laterality and in addition exhibit speech and other mo- tor disorders, temperamental instability and reading disability." Later, she modified her point of view somewhat and appeared to be prepared to admit that "specific dyslexia" may be more important as a cause of reading disability than she had originally thought.128 Daniels25 laid stress on the fact that virtually all children with severe reading retardation could be helped by appropriate remedial teaching and used this as an argument against the existence of any such condi- tion as "congenital word blindness." This argument, however, is not generally accepted as valid by psychologists and remedial teachers who have experience with large numbers of so-called "dyslexic children," most of whom are found to make good progress with appropriate treatment.10'26'27'31'43'44'116 It is difficult not to feel, with Critchley,21 that the picture that has developed in the minds of many educationalists and psychologists—that 422

The Nature of Dyslexia specific dyslexia is an irremediable, clearly defined disease entity with constant symptomatology and signs—is responsible for their not recog- nizing the prevalence of the syndromes of specific dyslexia described largely by medical authors.21'22 To some extent, however, medical authors have contributed to this misconception by overemphasizing the constancy with which, for example, directional confusion, mixed laterality, and a positive family history of reading disorders are found. In a recent, more open-minded study of the total population of 9- and 10-year-olds in the Isle of Wight, Rutter et al.119 found that 4% of children had reading ages measured on Neale's tests that were at least 28 months below their mental ages as assessed by the wise test. The mean Wechsler IQ of the children was 103.118'136 It was found that specific reading retardation was associated with considerable diffi- culties in arithmetic, severe problems in spelling, delay in the development of lan- guage and immaturity of language still evident on examination to age nine and ten years; inco-ordination; motor impersistence; right/left confusion; (possibly) diffi- culties in constructional tasks; and a strong family history of reading difficulties. There was no association between left handedness or mixed handedness and specific reading retardation. With this one exception, however, all the features said to be characteristic of "dyslexia" were found to be associated with specific retardation.119 Rutter118 studied the clustering of "dyslexic characteristics in individual children showing speech and language abnormalities, motor incoordina- tion, constructional difficulties, motor impersistence and right/left con- fusion." None of the 86 children with specific reading retardation showed all five characteristics, only five showed four of them, nine showed three, 20 showed two, 29 showed just one, and 23 children showed none. Rutter concluded that there was no general tendency for the items to cluster together and that the associations between the vari- ous developmental abnormalities were of a low order. He felt that his findings offered no support for a single syndrome of "dyslexia." A pos- itive family history of reading difficulties was not found more fre- quently in those with specific reading disability. Rutter recognized that these findings did not exclude the possibility that various syndromes were associated with difficulty in learning to read and considered that, "whatever the basic cause of the different types of specific reading re- tardation, the final state is frequently the result of a combination of biological, social and psychological factors." His ideas conform with those advanced by workers who believe that a number of syndromes 423

THOMAS T. S. INGRAM with characteristic neurologic and psychologic findings may contribute to the difficulties in learning to read found in children in any large population.40-70-75'109 STUDIES OF CHILDREN SUFFERING FROM BRAIN DAMAGE Studies of children suffering from cerebral palsy and other syndromes associated with nonprogressive brain damage sustained before, during, or shortly after birth inevitably influenced contemporary thought about the nature of reading and spelling difficulties in childhood. Lord85'86 emphasized the lack of correlation between mental age and educability in patients suffering from cerebral palsy and described the perceptual and visuomotor difficulties from which many children suffered, includ- ing some with relatively high intelligence. She observed that many dys- kinetic children (in whom involuntary movements were the presenting feature) could draw, whereas other spastic children, whose motor func- tions were less impaired, could draw less well because of associated per- ceptual difficulties. Strauss and Lehtinen123 summarized Strauss and Werner's work124 with figure background tests (marble board, tachisto- scopically exposed pictures, tactual motor tests) and other tests in chil- dren with brain damage, in many of whom behavioral abnormalities and epilepsy were shown, but not cerebral palsy. Cruickshank and Bice23 at- tempted to correlate the nature of the failures on psychologic tests with the different clinical diagnoses of cerebral palsy and the clinical severity of the condition. A more extensive review of the perceptual difficulties of children suf- fering from cerebral palsy, particularly figure-background relationships, was made by Cruickshank et al.24 They studied 110 nonhandicapped children and 325 children between 6 and 16 years old who suffered from cerebral palsy and had a minimal mental age of 6 years and IQ within average for age. Six tests of tactile and visual perception were given to the children. It was found that cerebral-palsied children made consistently poorer performances than the nonhandicapped children in four of the six tests administered. Spastics had more difficulty in carry- ing out the tests than children suffering from choreo-athetosis (dyski- netic cerebral palsy). The relationships between the tests were low, but performance on the tests did correlate with chronologic age. Floyer50 studied 72 cerebral-palsied children who were considered 424

The Nature of Dyslexia educable. The group was matched with normal children for sex, IQ, and chronologic age. It was found that tests most sensitive to lag or distur- bance in visuospatial perception tended to be poorly performed by the patients who suffered from cerebral palsy, especially the girls. They had difficulty in visuomotor tasks, such as assembling pieces of form board, block building from memory, copying simple designs on paper, and do- ing the progressive matrices of Raven.114 Floyer, like many other au- thors, emphasized that many of the difficulties on psychologic testing that she found in patients suffering from cerebral palsy could be inter- preted in terms of immaturity of functioning, rather than permanent disturbance of function that could be attributed to a particular brain lesion.2-33'34'125 The question as to how far the visuospatial difficulties and the asso- ciated difficulties in reading and spelling may be regarded as manifesta- tions of developmental lag in concept formation or as specific deficits unlikely to disappear with maturation is fully discussed by Aber- crombie,1 who concluded that it would seem that as far as perception is concerned, there is little evidence that cerebral palsied children see things in a distorted manner, though they may see them in a primitive or immature way, that is, they fail to make differentiations at the level of complexity which might be expected from their mental age. They can therefore be described as suffering from developmental lag in their perceptual skills. The bizarre drawings and other constructions which some of them make may seem to be unlike what normal children produce at any age, but it is possible that these also may be explained by a mixture of immature and more mature ways of performing. She notes, however, that although there is some evidence that the de- veloping brain is functionally disordered by localized damage in less spe- cific ways than the adult brain, it is perfectly possible that different kinds of perceptual constructive or cognitive difficulties resulting from chronic lesions at different sites might be revealed by more sophisti- cated psychologic tests. Some evidence for the latter view may be found intheworkofWedell.132'133 Birch and Lefford9 and Bortner and Birch11 emphasize the way in which tactile, visual, and auditory perceptions modify each other and affect behavior as children mature. They write9 : The evidence for normal children strongly confirms the view that the elaboration of intersensory relations represents a set of developmental functions showing age- 425

THOMAS T. S. INGRAM specific characteristics and markedly regular curves of growth. At the very least, the emergence of such relationships appears to be delayed in the "brain-damaged" chil- dren, a factor which may seriously limit possibilities for the normal utilization and integration of environmental information. They found that a high proportion of their "brain-damaged subjects" showed severe impairment of intersensory perception, which did not appear to improve between the ages of 5 and 18 years. Prechtl and Stemmer110 attempted to pick out a uniform neurologic syndrome among the many heterogeneous groups of hyperkinetic chil- dren who had been referred to a neurologist because of poor school per- formance. Fifty children whose major abnormality on neurologic and electroencephalographic examination was found to be the presence of choreiform movements were studied in detail. A high proportion showed additional minor neurologic abnormalities on careful exam- ination. Of the 50 children, 90% had "more or less trouble in reading." They were frequently described by their parents and teachers as being abnormally clumsy, distractible, and restless; they found sitting still or concentrating on a subject for long periods extremely difficult. Prechtl and Stemmer were inclined to attribute the learning difficulties of this group of children suffering from the "choreiform syndrome" to diffi- culties of visual fixation, instability of concentration, and a lag in the development of cerebral dominance and "complex functions." A high proportion of such patients score very poorly on tests of visuospatial perception and, as noted by Birch and Lefford,9 have difficulties in intersensory integration. A positive family history of difficulties in learning to read and spell was not noted in the account given by Prechtl and Stemmer of their studies.110 It is clear from the investigations of visuospatial and intersensory per- ception in brain-damaged children described above that a variety of handicaps that impair children's ability to learn to read and spell are found frequently. The extent to which their perceptual defects can be attributed to maturational lag and to damage to particular areas of the developing brain is still a subject for much discussion.80'82-87 Certainly, it is difficult to distinguish the reading and spelling errors made by chil- dren with known brain damage from those made by children with no evidence of brain damage but with a positive family history of reading and spelling difficulties. The finding that a high proportion of children who suffer from 426

The Nature of Dyslexia cerebral palsy and other manifestations of brain damage are slow to speak, have difficulties in learning to read and spell, and may perform poorly on tests of auditory and visuospatial perception has given rise to much speculation as to the causes of reading and spelling difficulties in the whole child community.69'72-73 PROSPECTIVE SUR VEYS Retrospective studies of series of children suffering from reading dis- ability have many drawbacks. If they deal with large population sam- ples, individual pupils tend not to be fully investigated by all the methods available in psychologic and medical research. Smaller popu- lations are more manageable, but children with significant difficulties in learning to read and spell are few and tend to be very heterogeneous, so that firm conclusions about the causes and nature of their difficulties cannot be made. Prospective studies in which groups of preschool chil- dren are selected for investigation by clinical and psychologic methods before they go to school and then re-examined and retested in their early school years are of great value. Three studies of this type will be described. Completed Studies The first study is described in Predicting Reading Failure by de Hirsch et a/.,29 which gives an account of a study of 53 children who came from homes in which English was the predominant spoken language, had IQ'S within one standard deviation of 100 as obtained on Form L of the Stanford-Binet Intelligence Scale (1937 Revision), and showed no significant sensory defects and no evidence of psychopathology. A wide variety of tests of "behavioural patterning, motility patterning, gross motor patterning, fine motor patterning, laterality, body image perception, visual perception patterning, auditory perceptual pattern- ing, receptive language tests, expressive-language tests and sentence de- velopment" were given, in addition to reading-readiness tests, while the children were in kindergarten. There were 37 tests in all. After 1 year at school, all the children were given standardized tests of reading, spelling, and writing; after another year at school, tests were repeated. The aim of de Hirsch and her colleagues was to develop a battery of 427

THOMAS T. S. INGRAM tests that could be given in the kindergarten period and could predict which children were likely to suffer from reading and spelling difficul- ties in later years. They found that a series of 10 tests—ability to use a pencil, the Bender Visuo-Motor Gestalt Test, the Wepman Auditory Discrimination Test, the Number of Words Used in a Story Test, tests of categorization, the Horst Reversals Test,67 the Gates Word Matching Test, two tests of word recognition, and one test of word reproduction— gave scores in the kindergarten period that correlated closely with the scores obtained on standardized tests of reading and spelling given at the end of the first two grades of schooling (ages 7 and 8). Eight chil- dren were placed in the class of "failing readers." They comprised the lowest 1 5% among the children tested; all of them scored zero on the Gray Oral Reading Test at the end of the first grade, and five of them scored zero again a year later. Six of the eight failing children were boys; five were noted to be "markedly hyperactive, distractable, im- pulsive and disinhibited; they needed many opportunities to move around the room, and became resentful when they were required to sit still." Interestingly, they showed no more ambilateral responses than did the other 45 children, but "the auditory-perceptual and oral- language tools of the failing readers were decidedly inferior to those of the remaining subjects." Four boys and four girls were categorized as "slow starters." They scored zero on the Gray Oral Reading Test at the end of the first grade, but achieved their expected level at the end of the second grade. Their reading and spelling difficulties appeared to be transient; as they developed and received instruction, their performance improved. Two boys and six girls were considered to be "superior achievers" both in reading and in spelling. De Hirsch et al. commented that the failing reader's perceptual, motor and linguistic responses were strikingly un- stable. As do chronologically younger children they functioned at a primitive and an undifferentiated level. Their fragmented figure drawings, their poorly synthe- sised Bender designs, their inability to organise parts of a story into a meaningful whole suggested a relatively low level of integrative competence. It was not, however, any failure on any single task that distinguished the failing readers from the other subjects but rather the accumulation of deficits. They thought the "accumulation of deficits" pointed to severe matura- tional lags. They argued that the relatively poor scores of prematurely born children, compared with those of children born at term and having 428

The Nature of Dyslexia equivalent intelligence, reported by Kawi and Pasamanick76 and Drillien36 and confirmed by their own studies, might also be explained on the basis of retarded maturation of higher nervous activity: In summary these findings as well as clinical experience support our supposition that there is indeed a close link between a child's maturational status at kinder- garten age and his reading and spelling achievements several years later. A relatively small but very detailed longitudinal study of the reading and spelling handicaps of 56 boys attending an upper-class school in the United States has recently been presented by Rawson.115 Rawson rated the severity of difficulties in learning to read and write in her pupils and considered that there was a continuum of language ability between those who were superior and those who could be considered "dyslexic." She categorized 20 children as having high, 16 medium, and 20 low language facility. Of the 20 children with low language facility, eight were categorized as suffering from moderate dyslexia and 12 as suffer- ing from severe dyslexia. It is to be noted, however, that four of the 12 in the latter category were admitted to school after the first grade be- cause there was a language re-education program in the school that the children's parents wanted to take advantage of. Rawson followed her pupils into adult life and was able to show that even those who seemed most handicapped by language disability achieved university degrees and professional positions in society in later life at least equal to those of their school fellows with high language- learning ability, even though they might have some residual difficulties in reading rapidly and especially in spelling conventionally. It is interest- ing to note how aware of their minor persisting difficulties many of her ex-pupils were as adults. Like MacMeeken,88 Rawson felt that difficul- ties in the environment contributed to, rather than caused, reading and writing difficulties. New Findings In 1961, the Medical Research Council supported a program of research into the problems of children 2J/2-5 years old with retarded speech de- velopment and their later educational problems in the Department of Child Life and Health, University of Edinburgh. As noted earlier, a number of papers had indicated that a high proportion of children with slow speech development later had difficulties in learning to read and 429

THOMAS T. S. INGRAM write.20'42-46'93-95'103 Rawson115 reports speech development problems in nine of her 12 most severely dyslexic subjects. Of the 78 children considered to suffer from developmental dyslexia studied by Ingram and Reid,75 more than half showed retardation of speech development; less formal studies of children in a speech clinic demonstrated that a high proportion of them had later difficulties in learning to read and write.70 To see whether it was possible to isolate one relatively "pure" type of dyslexia, it was decided to investigate what happened to a series of children with significantly retarded speech development once they went to school. The subjects were a group of 73 children in whom a diagnosis of speech retardation was made in the Speech Clinic of the Royal Hospital for Sick Children, Edinburgh, and subsequently con- firmed on the basis of tests of articulatory development and language development in the Department of Child Life and Health, University of Edinburgh. So that the effects of environmental influences and, in par- ticular, social differences would be minimized, children of only the two upper social classes (I and II according to the Registrar General's classi- fication) were chosen. A control group of 140 children of similar class was obtained, so that variables that might adversely affect the learning of reading and spelling (other than speech retardation in the clinical group) might be excluded. Excluded from both groups were children with any history that gave rise to suspicion of brain damage, abnormal behavioral development, hearing impairment, behavior disorders, or any neurologic abnormalities on examination. The hypothesis was that healthy children of average or superior intelligence who showed re- tarded speech development would later have more difficulties in learn- ing to read and spell than a comparable group of children without re- tarded speech development. This study is still incomplete, because it is impossible to test reading and spelling performance accurately before children have been in school at least 2 years. Up to October 1968, 78 control and 51 speech-retarded children had been tested after being in school for at least 2 years. Some preliminary results are shown in Table 2. Because the average IQ of patients in the control group was a little higher than that of the speech-retarded patients, 29 children in each group were matched for sex and Stanford-Binet IQ . These matched sub- groups showed the same differences as the entire group. There were very significant qualitative differences between the chil- 430

The Nature of Dyslexia TABLE 2 Analysis of Preliminary Data (to April 1968) on Later School Attain- ments of Speech-Retarded Children" Backward* Skill Group No. in Group No. % Reading Speech-retarded 51 15 29 Normal control 78 1 1 Spelling Speech-retarded 51 18 35 Normal control 78 5 6 Arithmetic Speech-retarded 51 4 8 Normal control 78 6 8 ^Derived from Mason. "Absolute backwardness is considered to be indicated by educational age 6 months below chronologic age of 7 years irrespective of IQ. dren who had a history of speech retardation and those with normal speech development. Only nine (18%) of the 51 speech-retarded chil- dren made a good start in reading; 14 (27%) started badly but seemed to "catch up" and had a reading quotient within 15 points of IQ at the time of test; the remaining patients were retarded in reading attainment. In comparison, only 15% of the control group of patients had difficulty in the initial stages of learning to read. These findings may be compared with those of de Hirsch.27 All the speech-retarded children except the nine (18%) who suc- ceeded in reading from the start gave evidence of perceptual inade- quacy120 of either visuospatial or audiophonic type. Of the 16 children who failed completely in learning to read, three had severe visuospatial difficulties, two had severe audiophonic difficulties, and 11 had diffi- culties of both types. Of 14 children with mild, moderate, or severe failure, four had visuospatial difficulties, six audiophonic, and four both. Of 12 who had problems in the early stages but were reading sat- isfactorily at the age of 7, four had continuing audiophonic difficulties with or without visuospatial difficulties, and the other eight had lost the audiophonic disabilities that had previously troubled them. This finding supports Schonell's observations120 that audiophonic difficulties dimin- ish in severity and frequency with increasing age. It also indicates that audiophonic inadequacy for reading may arise from a developmental lag, rather than from chronic inadequacy.56'135 431

THOMAS T. S. INGRAM It was not surprising to find that the subjects who suffered from slow speech development, many of whom had residual speech defects, ex- perienced audiophonic difficulties when they came to learn to read. It became increasingly apparent as the study proceeded, however, that many of the difficulties in learning to read suffered by the subjects with slow speech development were not of audiophonic type, but visuospa- tial. Mason91 made the interesting observation that children with speech retardation, tested before they had reached school age, showed signifi- cantly depressed scores on the Goodenough Draw A Man Test, com- pared with the control group. Mason considered that the relative failure of the subjects in the speech-retarded group could be considered as one aspect of maturational lag, inasmuch as the subjects "drew a man" in the same way as children in the control groups would when 2 or 3 years younger. The extent to which their relative inability to draw a man could be attributed to visuospatial disabilities and the extent to which those disabilities could be related to deficiencies in conceptualization are subjects for speculation.29'54'90 The interim findings of this still incomplete study indicate that speech-retarded children in the upper social classes in Edinburgh, irre- spective of their level of intelligence, are at a high risk of failing to learn to read and spell as quickly as children of similar intelligence and social class without a history of speech retardation. The risk of reading failure is as great as 75% when the degree of speech retardation is 18 months or more at the age of 4% years. At least 16% of the speech-retarded chil- dren so far tested meet the definition of a child suffering from "specific dyslexia"—i.e., a child who, in the absence of impaired intelligence, physical defects, poor motivation, or adverse environmental factors, nevertheless experiences severe difficulty in the learning of reading al- though he performs satisfactorily in the early school years in subjects independent of reading. The proportion of children considered to suffer from "specific dyslexia" is likely to increase considerably as the study proceeds. Reading disability did not appear to be associated with any evidence of organic disorders in the patients studied; rather stringent neurologic examination had failed to reveal any indications of brain abnormality. But the reading and spelling difficulties could not be attributed to en- vironmental difficulties. There appeared to be evidence of constitu- tional reading disabilities. These disabilities, however, did not take a single form. Some children were retarded in reading because they were 432

The Nature of Dyslexia unable to perform adequately in the audiophonic tasks demanded by reading, others because they had visuospatial difficulties. In a third group, both types of difficulty were apparent. Preliminary data suggest that the outlook for overcoming or outgrowing reading and spelling dis- abilities is most favorable when the difficulties are audiophonic. DISCUSSION The Reading Process What is known about the complex processes by which children learn to read and write with accurate spelling has been fully reviewed by Vernon,127'129 Schonell,120 Burt,16'17 and, from rather different stand- points, Vygotskii,130 Piaget,108 and Luna.87 Luria87 points out that the process of reading begins with the percep- tion of letters and then the analysis of their conventional phonetic value. "This is followed by a very complex process, causing the most obvious difficulty in education—the process of fusion of the phonetic letters into words." Isolated phonetic sounds have to be receded into complete syllables before they can be combined into whole words. As reading skill develops, the "analysis and synthesis of individual pho- netic letters is gradually contracted and simplified and is eventually transformed into the direct recognition of words by sight." Luria considers that this is a characteristic of fully developed reading skill, the third stage. This stage of reading skill is reached when the reader perceives immediately the likely meaning of groups of letters or words and begins to "scan" sentences. He learns to compare the ex- pected meaning from minimal clues given in the text with the meaning actually expressed, and it is only occasionally with difficult words that he has to resort to the earlier methods of detailed phonetic analysis and synthesis. The process by which the child develops "guessing reading" or reading sentences or even paragraphs on the basis of minimal clues is crucial to the development of fluent reading characteristic of literate adults. To recognize letters, some minimal visuospatial abilities are re- quired.52'53 Vernon127 points out that, to identify words, a child must be able to recognize individual letters and perceive their ordering in space if he is to be in a position to sound them correctly. In most cases, 433

THOMAS T. S. INGRAM while they are acquiring the ability to do that, most children learn to recognize some words by their characteristic shapes, and the "guessing reading" process described by Luria begins. Vernon notes that small children may not realize what details of shape and form are essential, and they are likely to fail to understand relationships of parts of a word to the whole word. In particular, they have difficulty in perceiving the significance of the ordering of words. Defects of this type have been demonstrated in a number of studies on children who are retarded in learning to read and spell.18'54 They tend to confirm the statement by Hermann59 that in many cases there is a fundamental disturbance "involving the categorical sphere of function which may be termed directional function": The directional disturbance is related to a failure of lateral orientation with refer- ence to the body-scheme, such that concepts of direction are either uncertain or abolished; the individual consequently has difficulty in orientating himself in extra- personal space. This difficulty in orientation has particular consequences for the ability to operate with symbols such as letters, numbers, and notes. A number of authors have commented on the similarity of the pro- cesses involved in distinguishing temporal sequences that determine the order of speech sounds in oral language and spatial sequences that deter- mine the order of written symbols in written material.89 Ilg and Ames68 found that transposition of letters within words and complete word re- versals persisted considerably later than letter reversals in reading and that was also true of children who had had difficulty in learning to read when they came to write. Other forms of substitution, however, were fairly frequent, especially within monosyllabic words. At some stage in reading development, children learn to identify word shapes in association with related word shapes in the sentence; they be- gin to read from general clues rather than from item analysis. The ages and stages at which this process begins to occur are variable from child to child, but it seems to be relatively late in children who are slow to read. The ways in which children learn to correlate visual symbols with sound symbols have been studied extensively, but no major conclusions have been reached. It is obvious, however, that, at some stage in their process of learning to read, children must learn how to correlate written symbols with their spoken equivalents. In English, as Vernon127 has de- scribed, there are great difficulties in doing so because of the large num- ber of unsounded written symbols and the variation in vowel sounds in 434

The Nature of Dyslexia different positions. Another difficulty is that sounded words make sense only in context. As Vernon writes: Thus the child has to learn to understand that (a) each word and its sound patterns are separate entities, with their peculiar, invariable and universal characteristics; (b) each word's sound pattern can be analysed into a succession of sounds with a char- acteristic and invariable sequence; (c) these unitary sounds can be generalised, in the sense that they occur in approximately the same form, but in different sequences, in different words; (d) the sounds correspond to different letter shapes visually per- ceived; but (e) unfortunately in the English language the relationships between sounds and visual percepts vary considerably from word to word. Vernon is somewhat cautious in attributing difficulties in learning to read and spell to audiophonic disabilities but admits that "the one uni- versal characteristic of non-readers suffering from specific reading dis- ability is their complete failure to analyse word shapes and sounds sys- tematically and associate them together correctly." Why even quite an intelligent child should fail to realise that there is a complete and invariable correspondence between printed letter shapes and phonetic units remains a mystery which, as we shall see ... , has not been solved. It must be attributed to a failure in analysing, abstraction and generalisation but one which, typically, is con- fined to linguistics. Perhaps the obvious syncretism and familiarity of spoken words makes it particularly hard to apply cognitive reasoning to their analysis. It is certain that in some cases only a drastic form of analysis proves efficacious such as that utilised in the Fernald and Keller Tracing Method.45 Variety of Disturbances It is apparent that the complex and interrelated functions required for the normal development of reading and spelling may be disturbed in a wide variety of ways. Children who have difficulties in recognizing shapes, patterns, and sequences of patterns are likely to have trouble when they are asked to identify letters in different sequences. Children with difficulties in recognizing sequencing, whether in spatial or tem- poral terms, are likely to have difficulties in conceptualizing sequences of written symbols or sound symbols and in transmitting one to the other.89 Difficulties in sequencing are likely to be more evident when the child tries to spell than when he tries to read. Difficulties in correlating the written with the spoken symbol are almost invariably found in children with reading and spelling diffi- 435

THOMAS T. S. INGRAM culties. It is difficult to account for them in modern theories of learn- ing, but the idea that sequencing in either temporal or spatial relation- ships may be impaired does make it possible to understand to some extent how both visuospatial and audiophonic difficulties may arise. Difficulties in relating written symbols to their spoken equivalents are found very frequently in children with slow speech development and in most of them are the major cause of retarded development of learn- ing to read and write. In 1957, it was possible for Vernon127 to write: Speech defects and slow language development have often been found in backward readers and may have been contributory to the retardation, but in the experimental study of these defects there has been no attempt to determine the frequency with which they appear in severe cases of disability as distinct from their occurrence in the merely backward. To some extent, the preliminary results of the study of children with retarded speech development in Edinburgh have demonstrated that there is a close correlation between the extent to which speech develop- ment is retarded and the extent to which the ability to learn to read and to spell is impaired. It is apparent, however, that there are numerous causes of failure to read and spell. Such environmental factors as fre- quent changes of school, inappropriate and inadequate schooling, fre- quent absences from school, mental defect, deficiencies of hearing, se- rious abnormalities of vision, and combinations of these all contribute to backwardness in learning to read and spell. But in a high proportion of children who are slow to learn to read and write—in spite of the fact that they are of average intelligence, come from stable homes, and have experienced "normal" educational experiences—other explanations of their educational disabilities must be sought. A variety of clinical syndromes have been described that may be recognized in children of average intelligence without gross physical handicap. Some of these are associated with recognizable neurologic abnormalities, as in the case of the "choreoid syndrome" of Prechtl, in children suffering from mild ataxic cerebral palsy, or in those with other indications of "minimal cerebral dysfunction." In many of these patients, it is found on close examination that educational disabilities are not confined to reading and writing, but extend to other subjects, including arithmetic.74 In patients with "minimal brain dysfunction," there are likely to be considerable variations in the degrees of visuospa- tial or audiophonic handicap suffered by different patients. 436

The Nature of Dyslexia Many patients who show serious specific retardation in the ability to learn to read and write do not have any indications of brain damage. Many, although not all, have a family history of retarded development in learning to speak or to read and write. In these patients, difficulties in learning to read and write may be largely visuospatial or audiophonic, or both types of difficulties may be demonstrated in test and learning situations. A number of different clinical syndromes of "specific" learning dis- ability may be defined. Some are predominantly "visuospatial" in type, others predominantly "audiophonic," and others a combination. Some patients in each category may exhibit weak lateralization of handedness and "eyedness," clumsiness, or a family history of retarded develop- ment of speech and of learning to read and write. The definition of the many syndromes that constitute "specific developmental dyslexia" or "specific dyslexia" is only now becoming possible. Fuller definition is important not only for academic purposes, but also for remedial education, so that teachers may devise appropri- ate programs of teaching for their pupils. I wish to acknowledge the help of my research colleagues in the preparation of this paper, particularly Mrs. Anne Mason and Mrs. Mary Mclsaac. This work has been supported by the Medical Research Council and the Scottish Council for Research in Education. I am grateful to Professor Forfar for his encouragement and to Miss Ursula Burnet for much secretarial help. REFERENCES 1. Abercrombie, M. L. J. Perceptual and Visuomotor Disorders in Cerebral Palsy. Little Club Clinics in Develop. Med. Child Neurol. No. 11. London: Medical and Information Unit of the Spastics Society and William Heineman Ltd., 1964. 136pp. 2. Abercrombie, M. L. J., P. A. Gardiner, E. Hansen, J. Jonckheere, R. L. Lindon, G. Solomon, and M. C. Tyson. Visual, perceptual and visuo-motor impairment in physically handicapped children. Percept. Motor Skills 18:561-625, 1964. 3. Bachmann, F. Uber kongenitale Wortblindheit (Angeborene Leseschwache). Abhandlungen Neuiol. Psychiat. Psychol. Grenzgebieten. 40:1-72, 1927. 4. Bastian, H. C. A Treatise on Aphasia and Other Speech Defects. London: H. K. Lewis Co., 1898. 366 pp. 5. Bateman, F. On Aphasia or Loss of Speech in Cerebral Disease. On Asphasia or Loss of Speech and the Localisation of the Faculty of Articulate Language. (2nd ed.) London: J. and A. Churchill, 1880. 420 pp. 437

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THOMAS T. S. INGRAM 88. MacMeeken, A. M. Ocular Dominance in Relation to Developmental Aphasia. W. H. Ross Foundation (Scotland) for the Study of Prevention of Blindness. London: University Press, 1939. 89. Masland, R. The neurologic substrata of communicative disorders. Paper presented at the Convention Programme of the American Speech and Hearing Association, Chicago, 1965. Quoted by M. W. Masland in "Listening skills and reading performance." Paper presented to the United Kingdom Reading Asso- ciation, Edinburgh, 1968. 90. Mason, A. W. Follow-up of educational attainments in a group of children with retarded speech development and in a control group. Paper presented to the United Kingdom Reading Association, Edinburgh, 1968. 91. Mason, A. W. Specific (developmental) dyslexia. Develop. Med. Child Neurol. 9:183-190, 1967. 92. Maxwell, A. E. A factor analysis of the Wechsler Intelligence Scale for Chil- dren. Brit. J. Educ. Psychol. 29:237-241, 1959. 93. McCready, E. B. Biological variations in the higher cerebral centers causing retardation. Arch. Pediat. 27:506-513, 1910. 94. McCready, E. B. Congenital word-blindness as a cause of backwardness in school children. Report of a case associated with stuttering. Penn. Med. 13:278-284, 1910. 95. McCready, E. B. Defects in the zone of language (word-deafness and word- blindness) and their influence in education and behaviour. Amer. J. Psychiat. 6:267-277,1926-1927. 96. Middlesborough Education Committee. Report of a Survey of Reading Ability. Middlesborough Head Teachers Association, 1953. 97. Ministry of Education. Reading Ability Pamphlet No. 18. London: His Maj- esty's Stationery Office, 1950. 98. Money, J. Dyslexia: a postconference review, pp. 9-33. In J. Money, Ed. Reading Disability: Progress and Research Needs in Dyslexia. Baltimore: Johns Hopkins Press, 1962. 222 pp. 99. Monroe, M. Children Who Cannot Read. Chicago: University of Chicago Press, 1932.205pp. 100. Morgan, W. P. A case of congenital word blindness. Brit. Med. J. 2:1378, 1896. 101. Morris, J. M. Reading in the Primary School: an investigation into standards of reading and their association with primary school characteristics; with a statistical approach by P. M. Grundy. National Foundation for Educational Research in England and Wales. Publ. #12. London: George Newnes, Ltd., 1959.179pp. 102. Ombredane, A. Le mechanisme et la correction des difficultes de la lecture connues sous le nom de ce'cite verbale congenitale. Rapports Psychiat. Schol. Congres Psychiat. Infant. Paris. 1:201-233, 1937. 103. Orton, S. T. Reading, writing and speech problems in children; a presentation of certain types of disorders in the development of the language faculty. In S. T. Orton, J. F. Fulton, and T. K. Davis, Eds. New York Academy of Medi- cine. Salmon Comm. for Psychiatry and Mental Hygiene. Thomas W. Salmon Memorial Lectures. New York: W. W. Norton and Co., 1937. 215 pp. 104. Orton, J. L. The Orton-Gillingham approach, pp. 119-145. In J. Money, Ed. The Disabled Reader: Education of the Dyslexic Child. Baltimore: Johns Hopkins Press, 1966. 421 pp. 105. Orton, S. T. Visual functions in strephosymbolia. Arch. Ophthal. 30:707-713, 1943. 442

The Nature of Dyslexia 106. Orton, S. T. "Word-blindness" in school children. Arch. Neurol. Psychiat. 14:581-615, 1925. 107. Park, G. E. Medical aspects of reading failures in intelligent children. Arch. Pediat. 76:401-409, 1959. 108. Piaget, J. Comments on Vygotskii's critical remarks concerning "The Language and Thought of the Child" and "Judgment and Reasoning in the Child" by Jean Piaget, pp. 1-14. In L. S. Vygotskii. Thought and Language. Cambridge, Mass.: M.I.T. Press, 1962. 168 pp. 109. Pond, D. Communication disorders in brain-damaged children. Proc. Roy. Soc. Med. 60:343-348, 1967. 110. Prechtl, H. F., and J. Stemmer. The choreiform syndrome in children. Develop. Med. Child Neurol. 4:119-127, 1962. 111. Rabinovitch, R. D. Dyslexia: psychiatric considerations, pp. 73-79. In J. Money, Ed. Reading Disability: Progress and Research Needs in Dyslexia. Baltimore: Johns Hopkins Press, 1962. 222 pp. 112. Rabinovitch, R. D. Reading and learning disabilities, pp. 857-869. In S. Arieti, Ed. American Handbook of Psychiatry. Volume I. New York: Basic Books Inc., 1959.999pp. 113. Rabinovitch, R. D., A. L. Drew, R. N. DeJong, W. Ingram, and L. Withey. A research approach to reading retardation, pp. 363-396. In R. Mclntosh and C. C. Hare, Eds. Neurology and Psychiatry in Childhood. Proceedings of the Assoc. for Research in Nervous and Mental Diseases. Volume XXXIV. Balti- more: Williams and Wilkins, 1954. 504 pp. 114. Raven, J. C. Guide to Using Progressive Matrices. London: George G. Harrap and Co., 1947. 115. Rawson, M. B. Developmental Language Disability: Adult Accomplishments of Dyslexic Boys. Baltimore: Johns Hopkins Press, 1968. 127 pp. 116. Riis-Vestergaard, I. Treatment at the Word-Blind Institute, Copenhagen, pp. 15-22. In A. W. Franklin, Ed. Word-Blindness or Specific Developmental Dyslexia. London: Pitman Medical Publishers, 1962. 148 pp. 117. Rutherfurd, W. J. The aetiology of congenital word-blindness; with an ex- ample. Brit. J. Child Dis. 6:484-488, 1909. 118. Rutter, M. The concept of dyslexia. Paper presented to the Sixth International Study Group on Child Neurology and Cerebral Palsy organized by the Spastics Society, Oxford, 1968. (to be published) 119. Rutter, M., W. Yuill, J. Tizard, and P. Graham. Severe Reading Retardation: Its Relation to Maladjustment, Epilepsy and Neurological Disorders, (to be published) 120. Schonell, F. J. Backwardness in the Basic Subjects. Edinburgh: Oliver and Boyd, 1942.506pp. 121. Schonell, F. J. The Psychology and Teaching of Reading. Edinburgh: Oliver and Boyd, 1945. 128pp. 122. Stephenson, S. Six cases of congenital word-blindness affecting three genera- tions of one family. Ophthalmoscope 5:482-484, 1907. 123. Strauss, A. A., and L. E. Lehtinen. Psychopathology and Education of the Brain Injured Child. Vol. 1. New York: Grune and Stratton, 1947. 206 pp. 124. Strauss, A. A., and H. Werner. Finger agnosia in children. With a brief discussion on defect and retardation in mentally handicapped children. Amer. J. Psychiat. 95:1215-1225,1939. 125. Taylor, E. M. Psychological Appraisal of Children with Cerebral Defects. Cambridge, Mass.: Harvard University Press, 1959. 499 pp. 443

THOMAS T. S. INGRAM 126. Thomas, C. J. Congenital "word-blindness" and its treatment. Ophthalmo- scope 3:380-385, 1905. 127. Vernon, M. D. Backwardness in Reading: a Study of its Nature and Origin. Cambridge: Cambridge University Press, 1957. 227 pp. 128. Vernon, M. D. Specific dyslexia. Brit. J. Educ. Psychol. 32:143-150, 1962. 129. Vernon, M. D. The Experimental Study of Reading. Cambridge: Cambridge University Press, 1931. 109 pp. 130. Vygotskii, L. S. Thought and Language. Mass. Inst. of Technology Studies in Communication XXI. Cambridge, Mass.: M.I.T. Press, 1962. 168 pp. 131. Warburg, F. Uber die angeborene Wortblindheit und die Bedeutung ihrer Kennt- nis fur den Unterricht. Zeit. Kinderforsch. 16:97-113, 1911. 132. Wedell, K. The visual perception of cerebral palsied children. J. Child Psychol. Psychiat. 1:215-227, 1960. 133. Wedell, K. Variations in perceptual ability among types of cerebral palsy. Cereb. Palsy Bull. 2:149-157, 1960. 134. Weintraub, S. Visual perceptual factors in reading. Paper presented to the United Kingdom Reading Association, Edinburgh, 1968. 135. Wepman, J. M. Dyslexia: its relationship to language acquisition and concept formation, pp. 179-186. In J. Money, Ed. Reading Disability: Progress and Research Needs in Dyslexia. Baltimore: Johns Hopkins Press, 1962. 222 pp. 136. Yule, W. Predicting reading ages on Neale's Analysis of Reading Ability: Brit. J. Educ. Psychol. 37:252-256, 1967. 137. Zangwill, O. L. Asymmetry of cerebral hemisphere function, pp. 51-62. In H. Garland, Ed. Scientific Aspects of Neurology. Baltimore: Williams and Wilkins, 1961.264pp. 138. Zangwill, O. L. Cerebral Dominance and Its Relation to Psychological Func- tion. (The Henderson Trust Lectures, no. 19.) Springfield: Charles C Thomas, 1960.31pp. 139. Zangwill, O. L. Dyslexia in relation to cerebral dominance, pp. 103-113. In J. Money, Ed. Reading Disability: Progress and Research Needs in Dyslexia. Baltimore: Johns Hopkins Press, 1962. 222 pp. 444

ARCHIE A. SILVER / ROSA A. HAGIN Visual Perception in Children with Reading Disabilities This presentation discusses two questions: What defects in visual per- ception are associated with delayed acquisition of reading in childhood? What happens to those defects as the child grows into adulthood? Our own investigations—dealing primarily but not exclusively with children who were 7-12 years old, who had full-scale intelligence quo- tients of at least 85 on the Wechsler Intelligence Scale for Children, and whose acquisition of reading was delayed—have led us to recognize a syndrome in which a basic component appears to be disorientation in space and in time. This disorientation is reflected in specific temporal and spatial distortions in the visual, auditory, and kinesthetic-tactile perceptual modalities and in general body-image orientation. For example, temporal sequencing of sound may be defective. In tactile and body-image perception, there may be impairment in spatial orien- tation of right and left, up and down. There may be specific visual defects in discrimination, in figure-background perception, in visual- motor function, and in visual memory. Individual variations in perceptual defects charted in a.perceptual profile graphically illustrate that all combinations of defects may be found clinically. Visual defects, therefore, constitute only one area of difficulty in a broad spectrum of perceptual defects that is different in distribution and severity for each child. Perceptual investigation, too, is but one aspect of the total evaluation 445

ARCHIE A. SILVER / ROSA A. HAGIN of the child with a reading disability. In the last year, we have examined 50 first-graders who were sent to us because their language skills were significantly below those of their peers in age, intelligence, and educa- tional exposure. We found a very mixed etiologic group. In such a group, approximately one third will have the syndrome described (spe- cific perceptual defects), immature postural responses, and clinical evidence that clear-cut cerebral dominance for language is not estab- lished. Another one third will have this basic syndrome, but, in addi- tion, neurologic abnormalities in one or more areas: in muscle tone, power, and synergy; in cranial nerves; in deep, superficial, or pathologic reflexes; or in impulse control and autonomic lability. Of the remaining one third, an occasional child (two in our sample) will have a peripheral sensory defect. Four children were diagnosed as schizophrenic. One was found to be immature in all aspects of development and functioning at a defective level on intelligence testing. In three, emotional problems were considered to be the cause of language retardation, and in four children perceptual deprivation at critical ages was considered causal. Because of these complicated etiologic factors, we believe that evalua- tion of the child with a reading disability requires, at the very least, neurologic, psychiatric, psychologic, and educational examinations. We are concerned here with children whose language skills, as mea- sured by standard tests, are below those expected from their intelli- gence and educational experience and whose peripheral sensory apparatus is intact. The defects in visual perception that are associated with delayed acquisition of reading include defects in visual discrimina- tion, in visual-motor ability, and in visual memory. Although it may be difficult to isolate them, attempts to do so should be made, because they may reflect different aspects of brain function. In visual-motor dysfunction, for example, the critical defect may lie in the praxic ele- ment, not the discrimination one; and in defects in visual memory, complex association or cognitive factors may be involved, and not discrimination or praxis. Practically, these areas of visual perception may be studied by tasks of matching and recognition, of copying, and of recall, singly and in combination. VISUAL DISCRIMINATION The outstanding defect in visual discrimination is in orientation of a figure in space. Orientation may be affected not only in the right-left, 446

Visual Perception in Children with Reading Disabilities or vertical, plane, but in the horizontal plane, in the depth axis, or in various degrees of clockwise or counterclockwise rotation. The general problem of axial rotation was studied by Wechsler and Pignatelli35 as early as 1937. The ability to orient a figure in space correctly in all axes is not acquired until the age of 5, 6, or 7 years, depending on the test used. Garvey and Herman, working in our clinic, examined the perceptual maturation of 50 children, 4.5-5.5 years old, who made up the total population of a "normal" Head Start nursery. All the children easily recognized cylinders, rectangles, wedges, squares, and columns when the forms were presented in three or two dimensions. When, however, the wedge was presented in two dimen- sions in various spatial orientations, 19 of the 50 chose an incorrect orientation. How many of those 19 will have difficulty in learning to read or in some aspect of language development would be important to follow. A partial answer to this question is suggested by a study by Wechsler and Hagin,34 who investigated the problem of axial rotation in 50 first-grade children and 50 third-grade children in a middle-class suburban school. A portion of their study concerned the matching or visual discrimination of an asymmetric figure, shaped roughly like a lamb chop, imprinted in eight different positions representing the lamb chop in various axial rotations. Their data indicate that children who most frequently perceive the figure in its correct orientation show a higher degree of reading readiness, as measured by conventional tests, and make more rapid progress in beginning reading. Furthermore, there is maturation in this discrimination function from the first to the third grade: the frequency of rotational errors on recognition drops from a high of 13% in the first grade to 3% in the third grade. In short, a significant proportion of children who continue to have problems of visual spatial orientation will have difficulty in the acquisition of reading skills. We have further investigated the problem of visual spatial orienta- tion in older children by using the flag figure and the recognition of asymmetric matrices and overlapping forms. The flag figure consists of two crossed diagonal lines with a square drawn at the end of each, having the diagonal line as its base. In effect, it is a picture of four crossed flags. The flags are oriented in various directions; a 7-year-old child of average intelligence can easily recognize the flags in different orientations, but a child with a reading disability will have difficulty. Similarly, asymmetric matrix-like forms and complex overlapping 447

ARCHIE A. SILVER / ROSA A. HAGIN forms present a problem in recognition. Of 60 children with reading disabilities who were involved in a perceptual training project over the last two years, only ten were initially able to recognize and match simple, asymmetric, and complex forms. In our experience, 80% of children with reading disabilities have difficulty with the orientation of visual stimuli in space. This is at a level of visual recognition and does not involve verbal symbols. Spatial orientation is further confused in the child with a reading disability, when a figure-background problem is introduced. To minimize the influence of the motor component, figure-background problems may be studied by recognition of pictures, hidden within a background by a variety of techniques.18'23'32'33 Our own preference for children 8-11 years old has been the marble board. This test, adapted from Werner and Strauss,36 has been standardized by Grain and Werner.4 It uses identical square boards, each having 10 rows of 10 depressions. The depressions are painted black, the remainder of the board gray. Standard designs are formed with black marbles in the de- pressions, and the subject is asked to reproduce the design with marbles on a second board. This test eliminates a verbal factor present in the hidden images, and becomes a problem in visually distinguishing the orientation of the test pattern. It reduces but does not eliminate a motor factor, in that the marbles must be placed in the depressions to make the pattern. Of children with reading disabilities, 50% will have difficulty with this task. Their errors appear to involve spatial orienta- tion and can be categorized into the following groups: (1) difficulty in constructing diagonals and angles, (2) omission of marbles in the figure, (3) displacement of the figure or its parts, and (4) the use of tactile clues, such as fingering the depressions. That these errors are not praxic is shown if a color contrast (e.g., using red marbles) enables the child to reproduce the figure correctly. The ability to clearly distinguish a figure from the background may be examined by means of ambiguous figures, such as the familiar vase-face (Rubin's goblet figure) illusion. Normally, awareness of the figure or background will alternate—at one time the profile and at another time the vase will be the foreground. Why this fluctuation occurs is not known.24 The number of apparent changes per minute, however, may be determined. The frequency of apparent change de- creases with age and with structural damage to the central nervous system. In children with reading disabilities, a bimodal curve is ob- 448

Visual Perception in Children with Reading Disabilities tained, at one end of which are those with extremely rapid fluctuations (20-30 per minute), and at the other, those with extremely slow fluctu- ations (4-6 per minute). The significance of this test is unknown, and the test itself, relying on subjective reporting by the child, may not be reliable. On the basis of having studied their discrimination of geometric forms and their errors in figure-background tests, we may postulate that, symptomatically, a significant defect in the visual perception of children with reading disabilities lies in defective ability to orient a figure in space correctly. This defect does not necessarily imply struc- tural damage to the brain, but it does suggest a lag in the maturation of some brain function. This hypothesis may be investigated further by tachistoscopic methods; the emergence of primitive patterns of visual discrimination may be observed in normal children as the exposure time is successively reduced.27 These primitive patterns are similar to those which children with reading disabilities will display with un- limited exposure time. VISUAL-MOTOR FUNCTION Visual-motor function adds the functions of fine motor coordination and of praxis to the capacity for precise visual discrimination. Even if tests of visual discrimination are normal and there are no defects in fine motor coordination, visual-motor function may be disturbed because of a defect in the ability to imitate motor patterns. Frequently, a child can recognize that his copy of a pattern is incorrect, but he cannot make it correspond. Praxis, like any other function, has a sequence of maturation, with the primitive visual-motor pattern proceeding from scribbles to connected loops drawn clockwise in a horizontal row, to single closed loops, to crossed horizontal and vertical lines, to the square, to the triangle, and finally to the diamond at age 7.27 Crossed diagonal lines require approximately 8 years for maturation.1 Delay in the maturation of visual-motor function has been found by de Hirsch et al.,s Coins,8 and Monroe21 to correlate significantly with the pres- ence of reading disability. Our own observations of children with reading disabilities reveal that, on the Bender-Gestalt test, they perform below their expected age and intelligence. Significant defects are indicated by four charac- teristics: difficulty with angulation, either immature or actually stel- 449

ARCHIE A. SILVER / ROSA A. HAGIN late; a tendency to verticalize the diagonals, and to rotate entire figures toward the vertical; replacement of dots with primitive loops; and use of cues, such as the edge of the paper or a previously drawn figure. These findings consistently appear, in greater or lesser degrees, in approximately 90% of children with reading disabilities. The findings agree with those of Keogh.13 There are, of course, many other ways of testing visual-motor function—for example, the copying of geometric figures other than the Gestalt form8-21; the parallelogram test of Luria,18 in which the patient is to place a circle in the appropriate corner of a parallelogram to reproduce a given parallelogram and circle, all presented in various spatial orientations; the Kohs block test10 or the block-design subtest of the Wechsler Intelligence Scale for Children; and Raven's progressive matrices.25 The latter example, however, may involve cognitive pro- cesses other than visual-motor function. Such tests as the Gottschaldt figures, used more for adults,11 combine a figure-background problem with a visual-motor one. The defects in visual-motor function found in children with reading disabilities, like defects in visual discrimina- tion, may be interpreted as being related to spatial orientation. These defects are characterized by performance on a lower level of the maturational scale than expected from the age and intelligence of the child. DEFECTS IN VISUAL MEMOR Y Tests of recall of visual stimuli appear in most surveys of visual per- ception in children with reading disabilities. Monroe,21 for example, required children to draw from memory 16 designs that were presented in groups of four for 10 sec/group. In a portion of the Wechsler and Hagin study34 cited earlier, recall of the stimulus card exposed for 3 sec and then removed from sight proved to be more difficult than visual discrimination, and a poor score in recall was significantly related to poor reading in both first- and third-graders. The Benton visual reten- tion test,2 however, as reported in 20 children aged 9-11 years with reading disabilities, revealed only two children with defective perfor- mance.16 Our own observations indicated that, when recall involved the mem- ory of asymmetric figures or the memory of a visual sequence, problems arose. The normal 6-year-old, for example, can remember a series of 450

Visual Perception in Children with Reading Disabilities five small and large square blocks arranged in a sequential pattern; if the blocks are removed, he can replace them in their correct sequence. The 5-year-old has difficulty with this, and when the square blocks are replaced by wedges with differing orientation, even the 6-year-old will falter. Our children with reading disabilities cannot draw from memory the complex asymmetric figures or sequences of overlapping forms that they have just seen for as long as 15 sec. Whether this is a problem of visual memory or a reflection of the visual-motor problem cannot always be determined from this test alone but becomes apparent in the context of a total examination. Problems in visual memory in children with reading disabilities may be interpreted primarily as defects in spatial orientation. This defect is also seen in visual discrimination, in visual figure-ground perception, and in visual-motor functioning. The visual discrimination function may be said to be immature if there are problems in orienting a figure in space or discriminating a figure against the intruding background. Visual-motor function may be said to be immature if there is a ten- dency to revert to primitive verticalization and spatial confusion. That these are difficult problems can be seen in efforts to correct them through training. Of 60 children involved in a perceptual-training project, 38 required more than 10 hr and three required more than 25 hr of training to learn to recognize, copy, and recall even the sup- posedly simple geometric forms; the total length of individual training sessions required to progress from simple forms to complex forms reached well over 50 hr for each child. What happens to these defects? As the child grows into adulthood, these perceptual areas do show some evidence of maturation. The de- fects do not, however, completely disappear, and some evidence of reading disability persists even if there is adequate academic, social, and vocational progress.26 A follow-up study of 24 children with reading dis- abilities originally studied and treated in our clinic between 1949 and 1951 and studied again as young adults in 1961 and 1962, some 10-12 years later, revealed the persistent stamp of reading disability.29 In visual-motor testing, for example, the Bender-Gestalt drawing does show statistically significant improvement in rotation and verticalization and in ability to cross the midline. Angulation difficulties, however, per- sist, and although the degree of rotation is decreased, some slight primi- tive tendency toward verticalization remains. When contrasted with a control group of adequate readers from a similar clinical population, 451

ARCHIE A. SILVER / ROSA A. HAGIN these primitive tendencies in those who had reading disabilities as chil- dren are seen more clearly. In the area of figure-background perception, those with reading dis- abilities in childhood made significantly more errors than did controls in reproducing diagonals, in omitting marbles, in displacement of the fig- ures, and in use of tactile or color cues. Twelve years later, significant improvement was noted in only one area: omissions of marbles from the figure. Although improved, the adult with a reading disability still suf- fered from a figure-background problem, because he had not attained the maturation level of the control groups. If we analyze our data in terms of adult reading achievement, we find that the adequate readers tend to have been less severely retarded in reading when tutoring was initiated, that as children they had fewer per- ceptual problems, and that as children they had a significantly greater proportion of verticalization and rotation errors in visual-motor perfor- mance, but significantly fewer figure-background problems. Diagnosti- cally, there were fewer "soft" neurologic signs (i.e., signs of minimal brain damage).29 Other investigators have considered the effect of training in perception on various aspects of reading behavior. Among these are Levin and Watson,17 Staats et al. ,31 Monsees,22 Elkind et al. ,6 Budoff and Quinlan.3 and McNeil and Stone.20 The persistence of perceptual defects into adulthood, however, led us to consider the possibility of a direct attack on perceptual defects in childhood. Instead of circumventing them, we would try to train them out. Accordingly, we devised training techniques to correct the specific perceptual defects found in careful evaluation of each child. In the visual area, this consisted primarily of the recognition, copying, and recall of simple and asymmetric, matrix-like, and over- lapping forms, exercises in the orientation of forms in space, and training in the isolation of the figure from the background. Details of this experi- ment may be found in Silver et al. a0 After 50 sessions of perceptual training, the overall Koppitz15 scores on Bender-Gestalt testing are improved significantly at the 0.001 con- fidence level (Wilcoxon test).28 Examination of the error characteristics reveals improvement in angulation, verticalization, rotation, accuracy of joining, and ability to change direction in card 6, all at the 0.005 level of confidence, using the chi-square test. On the marble-board test of figure- background perception, the total score, using Goldenberg's system,9 is significantly improved (at the 0.001 level). Individual error character- 452

Visual Perception in Children with Reading Disabilities istics show significant improvement in omission of marbles, angulation errors, and diagonal errors at the 0.0005 level and in displacements at the 0.005 level. These improvements are not made after control sessions. It appears, therefore, that specific training of visual discrimination, visual- motor copying, and visual memory can indeed result in improved ability in these functions. Is this reflected in improved reading ability? Of 58 children with reading disabilities treated in our program of perceptual correction, 43 improved in Koppitz scores and 15 did not. Oral reading and reading comprehension improved significantly in the children with improved Koppitz scores; improvement was not significant in the 15 whose Koppitz scores did not improve. In summary, the evaluation of visual perception is but one part of the perceptual examination of the child with a reading disability. Perceptual study is, in itself, only one part of the neurologic, psychiatric, psycho- logic, and educational evaluation considered minimal for the under- standing of such a child. Defects in visual perception are, however, associated with delayed acquisition of reading. In visual discrimination, the outstanding defect is in orientation of a figure in space and in clearly discriminating a fore- ground figure against an intruding background. In visual-motor function, the main defect is immaturity in ability to reproduce a correct spatial orientation of a figure, and specific immaturities appear in the retention of a primitive tendency to verticalize figures and in difficulty with angu- lation. Defective visual memory shows up in the difficulties in spatial orientation and memory of sequences of visual forms. As the child grows into adulthood, these defects tend to lessen; but usually they do not completely disappear, and some evidence of dys- function remains. Visual perceptual defects in childhood may be reduced by training procedures that use direct perceptual stimulation. Improvement in per- ception appears to be associated with improvement in oral reading and in reading comprehension. CEREBRAL DOMINANCE* The functional relationship between the two cerebral hemispheres has been a focus of our attention in attempting to understand the problems ' I his section was added after the conference. 453

ARCHIE A. SILVER / ROSA A. HAGIN of children suffering from developmental (specific) reading disability and those with minimal neurologic signs. If we analyze the perceptual defects found in children with reading disabilities, we are impressed that in each perceptual area the defect may be interpreted as a defect in spatial or temporal orientation. This defect appears in the visual, auditory, and hap tic avenues of perception, and in the total body-image concept, where problems of right-left orientation are evident. If we attempt to carry our understanding of these perceptual defects back one step further, we suggest that defects in spatial and tem- poral orientation may in themselves be caused by a lack of clear-cut cerebral dominance. The finding of Sperry (see Sperry's presentation, p. 167) that the function of visual spatial orientation resides primarily in the lesser hemisphere, suggests that these children with reading dis- abilities have functional defects in the lesser hemisphere or in its relative balance with the dominant one. Suggestive evidence that the problem of cerebral dominance is im- portant in reading disability has been advanced by McFie19 (phi phe- nomena) and Kimura14 (dichotic auditory stimulation) and affirmed by our observations with the extension test of Hoff and Schilder.12 On the latter test, children with reading disabilities do not have clear-cut cerebral dominance. To be consistent with our hypothesis, then, the teaching of reading should theoretically begin with the establishment of clear-cut cerebral dominance for language. We do not know how to do this, but we have attempted to teach reading to children with reading disabilities by work- ing with the next step in their neurophysiologic maturation—namely, by improving the accuracy of their perceptual input. The object of this experiment was threefold: to determine whether we can reduce perceptual errors in children of school age by training, to ask what effect this training has on oral reading and on reading compre- hension, and to ask what effect this training has on our measures of cerebral dominance. As indicated, errors can be reduced by training; children then do better in oral reading and in reading comprehension. Also, in children in whom perceptual training is successful, tests for cerebral dominance change in the direction of more definite establishment of a dominant cerebral hemisphere. Our experiments in perceptual training were de- signed to give the children a firm perceptual basis for the later develop- ment of language skills. 454

Visual Perception in Children with Reading Disabilities Perhaps we should go back even further and attempt to develop cerebral dominance in the infant. If, as Gesell has suggested,7 cerebral dominance is based on tonic neck reflexes, an infant who does not ex- hibit a preferred reflex direction is prone to develop language disability. Our efforts, using Dr. Lipsitt's techniques (see p. 381), may well be to establish a preferred direction of tonic neck reflexes in the first year of life and thus enhance very early the perceptual pattern of functional asymmetry. The work reported here was supported in part by grants from the Field Foundation and the Carnegie Corporation of New York. The statements made and opinions ex- pressed are the responsibility of the authors. REFERENCES 1. Bender, L. A Visual Motor Gestalt Test and Its Clinical Use. Research Mono- graphs No. 3. New York: American Orthopsychiatric Association, 1938. 176 pp. 2. Benton, A. L. The visual retention test as a constructional praxis task. Confin. Neurol. 22:141-155, 1962. 3. Budoff, M., and D. Quinlan. Reading progress as related to efficiency of visual and aural learning in the primary grades. J. Educ. Psychol. 55:247-252, 1964. 4. Crain, L., and H. Werner. The development of visuo-motor performance on the marble board in normal children. J. Genet. Psychol. 77:217-229, 1950. 5. de Hirsch, K., J. J. Jansky, and W. S. Langford. Predicting Reading Failure: A Preliminary Study of Reading, Writing, and Spelling Disability in Preschool Children. New York: Harper and Row, 1966. 144 pp. 6. Elkind, D., M. Larson, and W. Van Doorninck. Perceptual decentration learning and performance in slow and average readers. J. Educ. Psychol. 56:50-56, 1965. 7. Gesell, A. L., F. L. Ilg, and G. E. Bullis. Vision: Its Development in Infant and Child. New York: Hoeber Medical Division, Harper and Row, 1949. 329 pp. 8. Coins, J. T. Visual Perceptual Abilities and Early Reading Progress. (University of Chicago Department of Education. Supplementary Educational Monographs, No. 87.) Chicago: University of Chicago Press, 1958. 108 pp. 9. Goldenberg, S. Scoring guide to Marble Board Test and Ellis Visual Designs Test, pp. 215-222. In A. A. Strauss and N. C. Kephart, Eds. Psychopathology and Education of the Brain-Injured Child. Vol. II. Progress in Theory and Clinic. New York: Grune and Stratton, 1955. 266 pp. 10. Goldstein, K., and M. Scheerer. Abstract and concrete behavior: an experimental study with special tests. Psychol. Monogr. 53:1-151, 1941. 11. Gottschaldt, K. Uber den Einfluss der Erfahrung auf die Wahrnehmung von Figuren; vergleichende Untersuchungen iiber die Wirkung figuraler Einpragung und den Einfluss spezifischer Geschehensverlaufe auf die Auffassung optischer Komplexe. Psychol. Forsch. 12:1-87, 1929. 12. Hoff, H., and P. Schilder. Die Lagereflexe des Menschen. Vienna: J. Springer, 1927. 182pp. 455

ARCHIE A. SILVER / ROSA A. HAGIN 13. Keogh, B. K. The Bender Gestalt as a Predictive and Diagnostic Test of Reading Performance. Doctor's Thesis, Claremont Graduate School, Claremont, Cali- fornia, 1963. (Dissertation Abstracts 24:2360, 1963) 137 pp. 14. Kimura, D. Cerebral dominance and the perception of verbal stimuli. Canad. J. Psychol. 15:166-171, 1961. 15. Koppitz, E. The Bender Gestalt Test for Children. New York: Grune and Stratton, 1964. 195 pp. 16. Leton, D. A. Visual-motor capacities and ocular efficiency in reading. Percept. Motor Skills 15:407-432, 1962. 17. Levin, H., and J. S. Watson. Writing as pretraining for association learning. J. Educ. Psychol. 55:181-184, 1964. 18. Luria, A. R. Higher Cortical Functions in Man. New York: Basic Books, Inc. 1966.513pp. 19. McFie, J. Cerebral dominance in cases of reading disability. J. Neurol. Neurosurg. Psychiat. 15:194-199, 1952. 20. McNeil, J. D., and J. Stone. Note on teaching children to hear separate sounds in spoken words. J. Educ. Psychol. 56:13-15, 1965. 21. Monroe, M. Children Who Cannot Read. Chicago: University of Chicago Press, 1932.205pp. 22. Monsees, E. K. Temporal sequencing and expressive language disorders. Ex- ceptional Child. 35:141-147, 1968. 23. Poppelreuter, W. Die psychischen Schadigungen durch Kopfschuss. Volumes I and II. Leipzig: Voss, 1917. (Cited in Luria.18) 24. Prentice, W. C. H. Aftereffects in perception. Sci. Amer. 206:44-49, 1962. 25. Raven, J. C. The 1956 revision of the matrices test. Bull. Brit. Psychol. Soc. 32: Inset p. 3, 1957 (abstract). 26. Rawson, M. B. Developmental Language Disability: Adult Accomplishments of Dyslexic Boys. Baltimore: Johns Hopkins Press, 1968. 127 pp. 27. Schilder, P. Contributions to Developmental Neuropsychiatry. New York: Inter- national Universities Press, Inc., 1964. 407 pp. 28. Siegel, S. Nonparametric Statistics: for the Behavioral Sciences, pp. 75-83. New York: McGraw-Hill, 1956. 312pp. 29. Silver, A. A., and R. A. Hagin. Specific reading disability: follow-up studies. Amer. J. Orthopsychiat. 34:95-102, 1964. 30. Silver, A. A., R. A. Hagin, and M. F. Hersh. Reading disability: teaching through stimulation of deficit perceptual areas. Amer. J. Orthopsychiat. 37:744-752, 1967. 31. Staats, C. K., A. W. Staats, and R. F. Schutz. The effects of discrimination pre- training on textual behavior. J. Educ. Psychol. 53:32-37, 1962. 32. Strauss, A. A., and N. C. Kephart. Psychopathology and Education of the Brain- Injured Child. Vol. II. Progress in Theory and Clinic. New York: Grune and Stratton, 1955. 266 pp. 33. Strauss, A. A., and L. E. Lehtinen. Psychopathology and Education of the Brain-Injured Child. Vol. I. Fundamentals and Treatment of Brain-Injured Chil- dren. New York: Grune and Stratton, 1950. 206 pp. 34. Wechsler, D., and R. A. Hagin. The problem of axial rotation in reading dis- ability. Percept. Motor Skills 19:319-326, 1964. 35. Wechsler, D., and M. L. Pignatelli. Reversal errors in reading: phenomena of axial rotation. J. Educ. Psychol. 28:215-221, 1937. 36. Werner, H., and A. A. Strauss. Pathology of figure-background relation in the child. J. Abnorm. Psychol. 36:236-248, 1941. 456

RICHARD L. MASLAND Implications for Therapy CLASSIFICATION Dr. Ingram (p. 405) has provided two types of classification. The first is etiologic; it includes organic disease, deviation of development, and less well-defined and more heterogeneous problems. The second is func- tional ; breakdown in the mechanisms involved may occur in any of sev- eral crucial stages of the process of learning to read. He has postulated three points of possible breakdown in this process: a failure of percep- tion, an inadequate language function, and a difficulty (or inability) in associating a visual symbol with the sound that it represents. Language Function Dr. Ingram has emphasized the linguistic element in reading—the im- portance of the pre-existence of an adequately developed language function in the child. His demonstration, also shown by Dr. Hirsh (see p. 231), of the inconstancy or lack of precision in the use of language at the time the child is expected to be learning to read is an important con- tribution to our understanding of the problem of the child at this age. Although Dr. Ingram recognizes the frequency of other factors in dys- 457

RICHARD L. MASLAND lexia, his prospective study documents clearly the relationship between deviations in language development and deviations in learning to read. Drs. Silver and Hagin, in the preceding paper, also recognize the diversity of the problem, but they emphasize the significance of disorders of per- ception. I have tried to relate these learning-to-read processes in a neuro- physiologic and neuroanatomic model that I think has some value for understanding the complexity of the process with which we are dealing and the various points of weakness at which a breakdown may occur. Anatomic Model In regard to the language function, the indications are that the centers for spoken language develop in the left hemisphere. Although consider- able plasticity still exists in the child, it is reasonable to assume that the analysis and use of auditory language, by the time a child enters school, are centered largely in the left hemisphere. Dr. Sperry (p. 167) has indicated that the appreciation, analysis, and recognition of geometric patterns and the orientation of self and objects in space constitute a function that, at least in the adult, is most skillfully carried out in the right hemisphere, particularly in the parietal region. At some point in the reading process, it is essential that there be established an association or a relationship between the visual pattern of a letter (which is, according to this concept, most effectively analyzed in the right hemisphere) and the meaning and sound of that letter, whose analy- sis is mediated in the left hemisphere. Experimental work3 strongly indi- cates that such interhemispheric associations are much more difficult to make than intrahemispheric associations. Teleologically, the visual process—the spatial orientation function— must be concentrated in a single hemisphere. As was emphasized by Dr. Sperry, this appears to be a very strongly unilateral function. The pigeon's eyes are on the sides of its head, and it has no stereoscopic vision: there is no uncrossed visual pathway in the visual tracts (Figure 1). If you cover one of the pigeon's eyes, teach it to discriminate between mirror-image objects with one eye, and reward it for selecting, say, the "b," and then cover that eye and permit the bird to attempt the task with the other eye, it will select the mirror image.1 The same experiment has been done in the monkey (Figure 2). If the optic chiasm is sectioned, the animal will have only a unilateral input to each occiput. Exactly the same results are observed in such a monkey that is first trained with one eye and then tested with the other.4 458

Implications for Therapy FIGURE 1 Interhemispheric transfer in the pigeon. A bird trained to peck the letter "b" with its left eye has the trace of this image relayed to the left hemisphere as "d." If it is then required to select between "b" and "d" with its right eye, the new image in the left oc- ciput is compared with the reversed image of the memory trace in the left hemisphere, and the mirror image, "d," is selected. (After Mello.1) (Reversals in the retina are disregarded for simplifi- cation.) Returning to the pigeon, how does one explain this phenomenon? If the animal is trained with the left eye, it becomes responsive to an image projected to its right occiput. This image, presumably, is similarly located in the visual association area, after which it is carried by a point-to-point mechanism as a mirror image to the other hemisphere. If the animal then observes the object with its right eye, the object that matches is, in fact, the reverse object, and not the original image. Integration Deficit From this experiment, it would appear that under ordinary circum- stances in the human there must exist in each hemisphere two con- flicting mirror images—one representing the direct visual input to that 459

RICHARD L. MASLAND FIGURE 2 Interhemispheric transfer in the monkey. If the optic chiasm of the monkey is cut, each eye will project only to the ipsilateral hemisphere, "b" seen with the right eye is projected only to the right hemisphere and relayed to the left hemisphere as "d." If the mon- key is then required to use its left eye to select between "b" and "d," it will select "d," because it corresponds to the memory trace of the left hemi- sphere. (After Noble.4) (Reversals in the retina are disregarded for simplifi- cation.) hemisphere, the other representing the mirror image relayed from the other hemisphere. There must be some mechanism for the suppression of the secondary image. However, as postulated by Orton,5 confusion might easily develop. In addition, the studies cited above suggest that the most effective integration of complex visual patterns is in the right hemisphere. There must be a consistent reversal whenever images are as- sociated with auditory language symbols mediated in the left hemisphere. Perceptual Deficits The convincing demonstration by Drs. Silver and Hagin of the nature of the perceptual deficits of their group of children lends some support to 460

Implications for Therapy the thesis that disturbance of the mechanism for suppression of the sec- ondary image underlies much of the children's disability. For example, they pointed out the tendency toward verticalization. Consider the prob- lem of the child who must distinguish between a vertical line and a hori- zontal line. That is simple, because the vertical line is exactly the same in the two hemispheres (as is the horizontal line). But consider the child who must distinguish between two diagonal lines that are, incidentally, also at a 90-deg angle. Theoretically, they might be no more difficult to distinguish than the horizontal and vertical lines. In this instance, the lines are confused in the two hemispheres and the child has to remember not only the appearance of the line but which hemisphere he is seeing it with. It is evident from Silver and Hagin's studies that there may be a very sound reason to assign a neurologic basis for the perceptual diffi- culties of these children. In respect to recognition of figures and symbols that are to be used for communication, in which an association must be established between the visual image and the language function, the child is being required, at first, to use two hemispheres, and an unusually dif- ficult task is being imposed on him. Milner's data2 suggest that, in the adult, although visual pattern rec- ognition is still most effectively mediated in the right hemisphere, the recognition of symbols is most effectively accomplished by the left hemi- sphere. This suggests that the problem of establishing association be- tween vision and language function is handled by having the center for symbol recognition develop in the left hemisphere, rather than in the right, where pattern recognition is ordinarily most effectively handled. Permanence Drs. Silver and Hagin have pointed out that these perceptual deficits are frequently permanent. There is, however, a tendency to speak of them as developmental lags. Although many children may learn to overcome their disabilities, for many, the disabilities nonetheless remain. Rawson6 has documented that, although her group of dyslexic boys managed to circumvent their disabilities and become effective readers, they were still different from average adults. They continued to have spelling diffi- culties, and the perceptual deficits sometimes persisted. We are talking about at least two different tasks when we speak of "reading disability": the task of the third-grader, who has to be able to read words, probably requires a concentration on pattern recognition 461

RICHARD L. MASLAND and precision of pattern recognition; and the task of the high-school stu- dent, who has to extract meaning with a minimum of cues, requires a different type of skill even though he must first have mastered the earlier task to some extent if he is to accomplish this one. There is much to sug- gest that the bright child, even if he continues to have a very serious per- ceptual deficit, manages to become a reasonably effective reader by using sketchy cues, which are all that is essential if one is able to extrapolate, as was discussed in this meeting. TRAINING GOALS I have some reservations about the hypothesis presented by Drs. Silver and Hagin that, to teach a child to read, one should address oneself to the underlying deficit in perception. There is a question of whether to teach to the deficit or around the deficit. The primary task required of the child is the recognition of a letter or word and its association with a sound or meaning. The teaching of perceptual skill is not an end in itself; we are not in- terested in training the child simply to perform well on the Bender- Gestalt test. The goal is the recognition of letters. Why not conduct perceptual training with the very objects or patterns that must ulti- mately be learned? For some, this may be aided by training and practice in distinguishing right from left. For others, haptic sensations may be useful to supplement weak or confused visual skills. For others, expla- nation, description, and logical analysis of letter shapes may be helpful. For still others, the use of a name or sound as a label for the symbol may be helpful. Earlier at this meeting (see presentation by Hirsh, p. 231), experimental evidence has been reported that indicates that a letter or trigram invested with a name is more readily recalled than one without a name. As to experimental evidence of the value of perceptual training, I know of only one adequately controlled study: that of Rosen.7 He in- vestigated early readers in 25 classrooms; half the children were given a half-hour of perceptual training each day, and the other half were given a half-hour of extra reading instruction. At the end of a semester, they were all tested for perceptual motor skill and reading. The children who had received the extra training in perceptual motor skills were better 462

Implications for Therapy in perceptual motor skills; the children who had received the extra train- ing in reading were better in reading. The results were the same when the classes were broken down into three equal groups of good, medium, and poor readers. There was, however, a small subgroup of 50 very handi- capped boys in whom perceptual motor training seemed to offer some advantage, but the results were not statistically significant. IMP LICA TIONS This summary of some of the possible neurologic, perceptual, and language-function deficits that may come into play in dyslexia leads to an important thesis: There is no panacea for dyslexia, and we are dealing with a wide diversity of problems and certainly with a high degree of individualization. In addition, the importance of early experience in the development of intellectual abilities must be emphasized. It is still un- clear in which of these children the disability has an organic or structural basis, and in which an environmental or experiential factor is responsible. The types of perceptual motor disability that Drs. Silver and Hagin de- fined are reportedly more common in the underprivileged segments of our society than among other groups. Is that because these children are more likely to be organically damaged? Is it because of unfavorable social and environmental experiences? Or is it because of a combination of the two? Greater attention must be paid to the specific developmental experiences related to the establishment of perceptual skills and to the language abilities that are essential in learning to read. REFERENCES 1. Mello, N. K. Concerning the inter-hemispheric transfer of mirror-image patterns in pigeon. Physiol. Behav. 1:293-300, 1966. 2. Milner, B. Brain mechanisms suggested by studies of temporal lobes, pp. 122- 145. In C. H. Millikan and F. L. Darley, Eds. Brain Mechanisms Underlying Speech and Language. Proceedings of a Conference Held at Princeton, New Jersey, Nov. 9-12, 1965. New York: Grune and Stratton, 1967. 261 pp. 3. Myers, R. E. Transmission of visual information within and between the hemi- spheres: behavioral study, pp. 51-73. In V. B. Mountcastle, Ed. Interhemispheric Relations and Cerebral Dominance. Baltimore: Johns Hopkins Press, 1962. 294 pp. 463

RICHARD L. MASLAND 4. Noble, J. Paradoxical interocular transfer of mirror-image discrimination in the optic chiasm sectioned monkey. Brain Res. 10:127-151, 1968. 5. Orton, S. T. Visual functions in strephosymbolia. Arch. Ophthal. 30:707-713, 1943. 6. Rawson, M. B. Developmental Language Disability: Adult Accomplishments of Dyslexic Boys. Baltimore: Johns Hopkins Press, 1968. 127 pp. 7. Rosen, C. L. An experimental study of visual perceptual training and reading achievement in first grade. Percept. Motor Skills 22:979-986, 1966. 464

MANAGEMENT OF CHILDREN WITH PERCEPTUAL AND READING DISABILITIES

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Early Experience and Visual Information Processing in Perceptual and Reading Disorders: Proceedings of a Conference Held October 27-30, 1968, at Lake Mohonk, New York, in Association With the Committee on Brain Sciences, Division of Medical Sciences, National Research Council. Edited Get This Book
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