and expressive vocabulary acquisition than speech training alone for many children with autism (Barrera et al., 1980; Barrera and Sulzer-Azaroff, 1983; Carr and Dores, 1981; Layton, 1988; McIlvane et al., 1984; Yoder and Layton, 1988). These findings support several conclusions for children with autism:
There is no evidence that use of AAC systems as collaterals to language instruction results in delays in the acquisition of speech, though specifying the advantages and disadvantages of using AAC in support of the development of speech in different populations remains a research question.
There is evidence that sign language enhances the use of speech for some children.
There is no evidence to suggest that sign language interferes with the development of speech.
Children with good verbal imitation skills demonstrate better speech production than those with poor verbal imitation skills, with or without AAC.
Children with poor verbal imitation skills are the best candidates for an AAC system, such as sign language, because they are likely to make poor progress in speech acquisition without AAC.
Seal and Bonvillian (1997) analyzed sign language formation of 14 low-functioning students with autism and found that the size of the sign vocabulary and accuracy of sign formation were highly correlated with measures of fine motor abilities and tests of apraxia, which is a neurogenic impairment of planning, executing, and sequencing movements (LaPointe and Katz, 1998). These findings support the role of a motor impairment in the level of competence attained in sign language and speech acquisition for children with autism, in addition to their social-communication and symbolic deficits. It is important to note that simple signs may be a support for children learning to speak or an additional mode of communication for children who have no speech or limited speech. However, it is very rare to find a child with autism who learns to sign fluently (in sentences) and flexibly. Signing is not generally an entry point into a complex, flexible system.
The use of visual symbol systems has received attention recently because of the limited outcomes with signs and the visual strengths of many children with autistic spectrum disorders. Picture Communication Symbols are the most commonly used line drawings for augmenting spoken language. Other visual symbols used include tangible or real objects, photographs, rebus symbols and several commercial symbol-to-word computer programs, such as Picture-It, Pix-writer, and Writing with Symbols 2000. Visual symbols have been used successfully with children with