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EARLY EXPERIENCE AND LEARNING IN VISUAL INFORMATION PROCESSING
EARLY EXPERIENCE AND LEARNING IN VISUAL INFORMATION PROCESSING
Pages 249-404
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From page 249... ...
Later, some are rather slow. EFFECTS OF LIGHT DEPRIVA TION ON PROTEINS One of the more dramatic landmarks dealing specifically with changes in the retina was a study by Brattgaard.2 He reared rabbits in darkness to the age of 10 weeks, and showed that the retinal ganglion cells were markedly retarded in development.
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From page 250... ...
Using hematoxylin and eosin staining permitted us to determine only that large numbers of ganglion cells in chimpanzees and monkeys eventually disappeared3 and that in cats the mean thickness of the inner plexiform layer of the retina was significantly reduced.7 At 90 days of age, normally reared rats showed more than seven times the concentration of RNA found in dark-reared littermates. The values for retinal ganglion cells were intermediate when the animals were reared in the dark for 90 days and then in normal diurnal lighting conditions for 60 days.
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From page 251... ...
The usual population of ganglion cells is markedly lower in cat, rat, or rabbit than in primates. This may permit the spontaneous firing of receptor cells, which occurs even in total darkness, to activate ganglion cells frequently enough to ensure their continuing viability.
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From page 252... ...
B, Prolonged total light deprivation from the age of 8 months to 24 months followed by normal light to the age of 8 years results in marked loss of ganglion cells (bottom layer)
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From page 253... ...
Effects of Visual Environment on the Retina less. The lower traces are of later responses to flashes given at 2-sec intervals and show that these effects persist.
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From page 254... ...
no light I 2 3 Successive flashes at 2 sec. intervals BEHA VIORA L COR RE LA TES I would like to indicate some behavioral correlates of lack of visual stimulation in the monkey at birth and shortly thereafter.
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From page 255... ...
These results fit the data of Wiesel and Hubel,5'11 showing that it takes patterned light, not diffuse light, to improve the responses of edgedetector units in the visual system. We do not think that this measure of acuity represents retinal improvement itself.
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From page 256... ...
Some of the differences indicate an advantage for the animals reared in diffuse light. Ocular pursuit of a moving light shows this slight advantage, perhaps: 1-3 days versus 3-12 days of patterned light experience.
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From page 257... ...
Development of visual acuity in rhesus monkeys deprived of patterned light during early infancy. Psychonomic Science 1:33-34, 1964.
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From page 258... ...
One animal, Snark, was seeing poorly; we are sure his visual acuity was low when he was 4 years old, and he was around 10 years old when we did the histologic examination, by which time he was hardly seeing at all. What the sections showed was a loss of ganglion cells.
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From page 259... ...
DR. VALVERDE: Did you mention that ganglion cells of the retina completely disappeared?
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From page 260... ...
DR. ALPERN: I have the impression that there were changes in the electroretinograms and that histologically you found that the chimpanzees, in contrast with the cats, had particular kinds of ganglion cells.
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From page 261... ...
VALVERDE / A RUIZ-MARCOS The Effects of Sensory Deprivation on Dendritic Spines in the Visual Cortex of the Mouse: A Mathematical Model of Spine Distribution INTRODUCTION Dendritic spines, a sequence of postsynaptic structures, are small, thornlike projections on the dendrites of neurons in the mammalian cerebral cortex.
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From page 262... ...
of the layer V pyramidal cells increases exponentially with distance from the cell body. These observations are based on the area striata of the mouse.
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From page 263... ...
It was found that the number of spines diminishes in mice enucleated on one side and in mice reared in complete darkness and that in both normal and visually deprived subjects the number of spines along apical dendrites increases exponentially with distance from the cell body. We would like to describe some morphologic details of dendritic spines and their relevant afferent connections, the effects of unilateral enucleation on the number and distribution of dendritic spines, and a mathematical model that defines the distribution of spines in the apical dendrites of the layer V pyramidal cells of normal and dark-raised mice.
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From page 264... ...
RESULTS Connections of Apical Dendritic Spines in Visual Cortex The synaptic terminals on dendritic spines can be observed easily on Golgi preparations. They appear in the form of short twigs derived from ascending or descending fibers that are closely parallel to the apical dendrites for considerable distances.
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From page 265... ...
The Effects of Sensory Deprivation on Dendritic Spines 30 fj MK1T PSR 13 FIGURE 1 Camera lucida drawing of portion of apical dendrite of a layer V pyramidal cell of visual cortex of normal 48-day-old mouse. Golgi method.
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From page 266... ...
, giving off a small twig for dendrite 1, which is another apical shaft of one pyramidal cell of layer V Effects of Enudeation on Number of Dendritic Spines: Further Details of Axospinodendritic Contacts In Golgi preparations, the apical dendrites of the pyramidal cells of layer V, which are 500-600n deep, as they ascend through layers V, IV, and III appear densely covered with spines, a series of short side appendages representing postsynaptic structures.
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From page 267... ...
The Effects of Sensory Deprivation on Dendritic Spines MK1T PSR 12.13 FIGURE 2 Camera lucida drawing of stellate cell of layer IV of area striata of normal 48-dayold mouse. Golgi method.
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From page 268... ...
There was no difference in the number of spines in segments of layer V between enucleated and normal animals of the same age. Figure 3 is a detailed camera lucida drawing of several portions of apical dendrites of deep pyramidal cells traversing layer IV.
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From page 269... ...
The Effects of Sensory Deprivation on Dendritic Spines > M150T PSL I4 FIGURE 3 Camera lucida drawing of portions of several apical dendrites of layer V pyramidal cells traversing layer IV of area striata of normal 48-day-old mouse. Details of synaptic contacts between various fibers and the dendrites can be seen.
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From page 270... ...
VALVERDE / A RUIZ-MARCOS M1UT PSL 14,15 ER FIGURE 4 Camera lucida drawing of portions of several apical dendrites of layer V pyramidal cells traversing layer IV of left area striata of 48-day-old mouse enucleated on right side at birth.
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From page 271... ...
The Effects of Sensory Deprivation on Dendritic Spines -- 0 FIGURE 5 Mosaic photomicrographic reconstruction of two apical dendrites of layer V pyramidal cells at the level of layer IV of area striata. A, 24-dayold mouse enucleated at birth; normal dendrite in the unaffected area striata with contacts in parallel.
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From page 272... ...
We have previously defined this relationship for apical dendrites of pyramidal cells of layer V in the area striata of 24day-old mice.43'47 It can be expressed by the following exponential equation: ye=ym(l-Ke-*
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From page 273... ...
The Effects of Sensory Deprivation on Dendritic Spines B FIGURE 6 Mosaic photomicrographic reconstruction of two apical dendrites of layer V pyramidal cells at the level of layer IV of area striata. A, 24-day-old mouse enucleated at birth.
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From page 274... ...
325 375 425 FIGURE 7 Number and distribution of spines in consecutive 50-/J segments along the apical dendrites of layer V pyramidal cells in the area striata. Sequence of mean values in four representative age groups of normal mice.
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From page 275... ...
The computer than printed out a graphic for each group of animals of the same age and condition with the experimental and theoretical distribution of the mean number of dendritic spines and their corresponding numeric values. The graphic output from this program, reproduced in Figure 8, corresponds to the distribution of spines along apical dendrites in normal 19-day-old mice.
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From page 276... ...
Chi value 2.409,8df,p<0.05. spines along apical dendrites of the layer V pyramidal cells of area striata in four groups of mice: Controls: 10, 14, 19, 21, 24, 36, 48, and 180 days old Raised in darkness since birth: 10, 14, 19, 21, 24, 36, 48, and 180 days old Enucleated on right side for study of distribution of dendritic spines in left area striata: 24 and 48 days old Enucleated on right side for study of distribution of dendritic spines in right area striata: 24 and 48 days old In all four groups of striate apical dendrites, the computer obtained highly significant adjustments to the theoretical distribution formu276
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From page 277... ...
. Equation 2 is valid to describe the distribution of spines along apical dendrites in the pyramidal cells of layer V of the area striata of the mouse at the ages and conditions just mentioned, yielding specific values of the coefficients IF, B, and K for each age.
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From page 278... ...
VALVERDE / A RUIZ-MARCOS SO "m " K 1.00860 B 0.00100 IF 0.00353 40 30 20 10 25 75 125 175 225 275 325 375 425 Distance From Cell Body in Microns FIGURE 9 Predicted distribution of dendritic spines along apical shafts of layer V pyramidal cells of area striata corresponding to 21-day-old mice that were raised in darkness.
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From page 279... ...
Distribution of Dendritic Spines in Visual Cortex of Enucleated and Dark-Raised Mice Mice enucleated at birth or raised in darkness are subject to a statistically significant diminution of the number of spines, which is most evident at layer IV in enucleated animals and throughout the apical dendrites in dark-raised animals of all the ages we have studied. Figure 10 is a graphic output from program RV-6803 corresponding to the distribution of dendritic spines in the affected area striata (con50 40 20 10 ym 400.00 B 0.00115 K 0.99982 IF 0.00365 25 75 125 175 225 275 325 375 425 Distance From Cell Body in Microns FIGURE 10 Experimental and theoretical distribution of dendritic spines along apical shafts of layer V pyramidal cells of affected area striata of four 48-day-old mice enucleated at birth.
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From page 280... ...
The differences from the averaged numbers of spines ob50 40 I V) a 30 j 8 6 z 20 10 ym 400.00 B -0.00184 K 1.02462 IF 0.00491 25 75 125 175 225 275 325 375 425 Distance From Cell Body in Microns FIGURE 11 Experimental and theoretical distribution of dendritic spines along apical shafts of layer V pyramidal cells of area striata of nine 48-day-old mice raised in darkness.
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From page 281... ...
The reconstruction has been drawn with values of the theoretical distributions given by the computer according to the mathematical model. The distance from the cell body along the apical dendrites is represented by the x-axis; the mean number of spines per 50-ji segment, by the y-axis; and age, by the z-axis.
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From page 282... ...
425 FIGURE 12 Three-dimensional reconstruction of distribution of dendritic spines along apical dendrites and evolution of distribution with age in normal and dark-raised mice. Reconstruction is based on theoretical distributions according to our mathematical model.
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From page 283... ...
The mathematical model that we have introduced39'46 demonstrates that the distribution of dendritic spines along the apical shafts of layer V pyramidal cells of the area striata in the mouse follows a mathematical law defined by Equation 2, which is valid for all age groups studied. If we now consider that every dendritic spine supports at least one synaptic connection, it is evident that the patterns of connectivity with respect to apical dendrites might be organized in part according to this law.
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From page 284... ...
VALVERDE / A RUIZ-MARCOS spines along the apical dendrites follows the same laws in man as in the mouse.
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From page 285... ...
The existence of a statistically significant diminution of the mean number of dendritic spines per segment in the apical shafts of layer V pyramidal cells of the visual cortex in dark-raised mice was first reported by Valverde.43 Changes in the morphology of the dendritic spines of young rabbits subjected to visual deprivation for the first 30 days of life have been described by Globus and Scheibel.16 Coleman and Riesen6 showed that stellate cells of layer IV in the visual cortex of cats reared in the dark have smaller dendritic length and fewer dendrites than those of normal animals. All these studies point out, as we have stated,43 that visual sensory deprivation affects the fine structure of the central nervous system and that some structural changes in nerve cells might occur as the result of experience.
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From page 286... ...
dendritic spines would not grow normally in the absence of normal visual inputs. Whatever the effect might be, the theoretical interest of our observations is obvious: they may give new clues to the anatomic plasticity of the brain in relation to behavioral and learning phenomena.
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From page 287... ...
Postnatal development of the visual cortex in darkness (mice)
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From page 288... ...
Number and distribution of the apical dendritic spines of the layer V pyramidal cells in man.
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Ruiz-Marcos. Light deprivation and the spines of apical dendrites in the visual cortex of the mouse.
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From page 290... ...
And, a more serious question, in the synapses of, say, the stellate cells on the pyramidal cells, or of the afferent fibers on either stellate or pyramidal cells, do the endings select a particular portion of the dendrite? Are they limited to only one portion, or might an afferent end on both the basal and the apical dendrites?
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From page 291... ...
In an albino infant, light is diffusely scattered across the retina, which results in lowered visual acuity. If this continual scattering of light is not remedied at an early age (for example, by means of an artificial pupil)
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From page 292... ...
Visual deprivation may also result from "suppression" of the turned eye's image. STRABISMUS AND VISUAL ACUITY Some children with strabismus develop in the turned eye an amblyopia, a reduction in visual acuity that cannot be improved with lenses or attributed to disease.
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From page 293... ...
TREATMENT N«72 ONS < I YR. TREATMENT D ««/o« 20/30 20/60 20/120 20/20 a 20/40 • 20/80 azO/200 LOSS OF FIXATION POST - TRE AT M E NT ACUITY FIGURE 1 Data of Claude Worth26 on 985 constant convergent squinters displayed to illustrate the influence of the onset of strabismus and delay in treatment on the development of visual acuity.
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From page 294... ...
If treatment was delayed by 3-12 months, a reasonable number of the children obtained normal or nearly normal acuity. If treatment was delayed by more than a year, most of the children did not obtain good visual acuity, and approximately 40% lost the ability to obtain monocular fixation.
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From page 295... ...
What is important is the evidence that amblyopia can be improved and even corrected in patients older than 8 years. NORMAL DEVELOPMENT OF ACUITY Let us now consider the development of acuity in the normal infant.
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From page 296... ...
In any case, it is clear that a child's visual acuity develops remarkably rapidly and reaches nearly its maximum by about 2 years of age. Somewhat related to our discussion on the development of acuity and amblyopia in human infants are the experimental results of Hubel and Wiesel.10 They cut loose the right medial rectus muscle of four no 100 >- a: -.
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From page 297... ...
If the embarrassment occurs during the developmental period of visual acuity (birth to 2 or 3 years) , then the ensuing amblyopia may include some portion due to impairment of normal development.
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From page 298... ...
I Visual acuity in the newborn human: a study based on induced optokinetic nystagmus recorded by electro-oculography.
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From page 299... ...
W Visual acuity of children, pp.
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From page 300... ...
But you do get amblyopia in the same species by playing with the process as it affects the central nervous system. This would suggest that the amblyopia does not arise simply from noncongruence, but can also arise from some problem in the lack of visual acuity itself.
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From page 301... ...
It appears that the two associated conditions in amblyopia are a deviant eye, which produces a lack of synergy in the two visual inputs, and one defocused retinal image. Each of these conditions has, of course, its counterpart in the Hubel and Wiesel studies.
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From page 302... ...
WILLIAM A MASON Information Processing and Experiential Deprivation: A Biologic Perspective Man's capability in the living world as a seeker and user of information is undeniably unique.
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Information Processing and Experiential Deprivation Other portions of this volume deal with the effects of experience on particular organs and processes in animal subjects. In contrast, my interest here is directed toward a broader set of questions.
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WILLIAM A MASON or a frog.
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From page 305... ...
Information Processing and Experiential Deprivation lus is a reaction to the "probability" that a suitable food object will be encountered.26 Likewise, a monkey's leap from one tree to another implies a statistical "faith" in the weight-bearing potential of tree limbs, the reliability of distance cues, and so on. From this point of view, all behavior points forward; it has a predictive or probabilistic component.3'4 Even the simplest-behaving organism is always of necessity playing the odds -- using information received to initiate some program of action as the most likely to result in success.
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From page 306... ...
WILLIAM A MASON by the complexity of the phenomenon being considered, by our knowledge of its history, and by our preference for "analytic" as opposed to "synthetic" terms.
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From page 307... ...
Information Processing and Experiential Deprivation substitute.18 In contrast with the frog's schematic fly, however, the monkey's primitive schema undergoes a rapid and progressive enrichment as development proceeds. As physical attributes and their arrangement in time and space become associated with a single source, "mother" emerges as an entity; she acquires object status.
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From page 308... ...
WILLIAM A MASON provision is made for creating behavioral stability by other means.
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Schemata may continue to develop under conditions in which the impetus and constraints that influence normal development are changed radically. The result is not behavioral disorganization, but a form of organization that reflects the particular circumstances of the rearing environment.
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WILLIAM A MASON analytic.
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From page 311... ...
An infant rhesus monkey with a thalidomide-induced deformity of the forelimbs not only walked bipedally, a behavior that is infrequent in normal animals but can be seen on occasion, but used its feet to groom its mother -- a pattern that to my knowledge has never been observed in an intact monkey, an "invention" in response to very special circumstances.24 Arousal Effects Another reliable consequence of early environmental restriction is a tendency toward fearfulness or heightened emotionality. The behavioral expressions of this effect are varied and depend on the particular 311
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WILLIAM A MASON species and the situation in which the animal is observed.
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From page 313... ...
subserving memory, attention, and similar functions. When activated, these processes cause a feedback to lower synaptic levels, where they can inhibit, facilitate or otherwise modify the input patterns of the more slowly conducting afferent fibers; in this fashion, they exert active control over the selection of information.
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WILLIAM A MASON Basic Cognitive Skills Certainly the strongest support for the thesis that high arousal exerts a disruptive effect on information processing is the poor performance of restricted animals on learning tasks.
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From page 315... ...
Information Processing and Experiential Deprivation inferiority was the tendency to persevere in the selection of a previously unrewarded object. Contrasting results have been obtained from similar tests performed with rhesus monkeys.
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From page 316... ...
if the test stimuli departed slightly from those to which the animal was exposed in its living cage. Transfer effects were no longer obtained, however, when the differences between the familiar stimuli and the test patterns were extreme.9'10'14 It thus seems clear that "casual" exposure to specific shapes during the rearing period will not only facilitate recognition of these patterns when they are later encountered in a discrimination-learning test, but will also lead to the establishment of some form of generalization "gradient." It becomes easier to recognize new stimuli that merely resemble the familiar pattern.
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From page 317... ...
, in spite of changes in conditions of presentation and the specific receptor surfaces that are stimulated. Ganz's conceptual approach developed out of research on animals raised under conditions of highly restricted visual input, which, strictly speaking, are outside the population that we are most concerned with here.
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From page 318... ...
WILLIAM A MASON Much of the evidence that has led me to this view has come out of deprivation experiments with nonhuman primates.
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From page 319... ...
Information Processing and Experiential Deprivation sponses toward inanimate objects that they have never before encountered. The frequency of these responses increases as the objects become more animal-like, or more representational.
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L Experiential deprivation and later behavior.
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Information Processing and Experiential Deprivation 30. Melzack, R
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Broadbent has recently criticized the methodology of the Harlow experiments, and has suggested that many of the conclusions about cognitive development are unjustified. Broadbent in particular feels very strongly that cognitive development is impaired, but this has not been shown yet.
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From page 323... ...
Information Processing and Experiential Deprivation performance -- and try to infer the antecedents from that. In the long run, we must do better.
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From page 324... ...
The exploring albino rat captured the stage from the brooding adult when the academy decided that public responses and easily induced drives were more critical than feelings, sensations, or thoughts. One of the stars of this decade is the human infant, and the theme turns once again to those mental processes called "cognitive structure." The ease with which loyalties to subjects or subject matters are broken is to be expected in a discipline as young as psychology.
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From page 325... ...
Continuity in Cognitive Development During the First Year of Life out a hand, and explore the object to see whether a quick determination is possible. If a few minutes of exploration proves fruitless, no worry; there are many other objects in the room that can be explored.
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From page 326... ...
Investigators of mental growth in the human infant before the 1960's 326
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From page 327... ...
Existing empiric data suggest that an infant may acquire a mental representation of an event by only looking or listening. An infant who has habituated to a repeated presentation of the same, initially novel, stimulus shows a dramatic change in fixation time when presented with a transformation of the stimulus.
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From page 328... ...
JEROME KAGAN CONTINUITY IN MENTAL DEVELOPMENT The mechanisms of establishment of cognitive structures are separate from the issue of continuity in level of cognitive development. Do infants who at some time show precocious acquisition of a class of structures remain precocious?
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From page 329... ...
Duration of orientation toward a visual stimulus ("fixation time") and vocalization during stimulus presentation are two reasonable indexes of an infant's degree of attention to an external event.
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From page 330... ...
Empiric support for the role of schema discrepancy on attention is suggestive, rather than definitive. At 4 months of age, achromatic illustrations of male faces elicit fixation times twice as long as those elicited by random shapes of varying num330
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From page 331... ...
Control children viewed all four stimuli for the first time at 4 months. The experimental infants showed shorter fixation times to all four stimuli than the controls.
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From page 332... ...
A subordinate theme is the possibility that vocalization during the early months has different meanings for the two sexes. Vocalization may display a sexual dimorphism in the human infant.
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From page 333... ...
These variables were coded by two independent observers watching from opposite sides of the crib, neither of whom could see the stimulus being presented to the child. Interobserver reliabilities were 0.97 for fixation time and 0.71 for duration of vocalization.
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JEROME KAGAN FIGURE 1 Achromatic faces shown to infants.
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From page 335... ...
Continuity in Cognitive Development During the First Year of Life FIGURE 2 Clay faces shown to infants.
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From page 337... ...
RESULTS Fixation-Time Stability Two fixation-time variables will be considered: average first fixation and average total fixation across all stimulus presentations in an episode. First fixation times averaged 8 sec at 4 months and 5 sec at 8 and 13 months.
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From page 338... ...
There was moderate continuity from 8 to 13 months for girls, but not for boys. It is relevant to add that both first and total fixation times at 8 months covaried positively with the parents' educational level for girls, but not for boys.
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From page 339... ...
A second source of support for the hypothesis that vocalization is a more faithful index of attentional processes in girls than in boys comes from the covariation between duration of first fixation and vocalization at 4 months. The distribution of first fixation times to each stimulus 339
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From page 341... ...
The probability of vocalizing 1 sec or more increased linearly with length of first fixation for girls, but was independent of fixation time for boys. The pattern of intercorrelations at 8 months furnishes additional support for the attentional significance of girls' vocalization.
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From page 342... ...
A final source of evidence is a longitudinal study in London in which 41 boys and 35 girls were seen at the ages of 6 and 18 months and 2, 3, 4, 5, and 8 years.33 At 6 and 18 months, each child was assigned a speech quotient from the Griffith's Infant Scale, which assessed spontaneous babbling at 6 months and use of words at 18 months. Although there were no sex differences in mean speech quotient at 6 or 18 months, the speech quotient was more stable from 6 to 18 months for girls than for boys (r = 0.51 for girls versus 0.15 for boys)
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From page 343... ...
Among the langur of northern India, for example, squeals and screams are observed more frequently among females than among males.21 More important, however, is the generally accepted premise that closely related strains or the sexes within a strain can differ in their typical reactions to states of arousal.6'39 This generalization might hold for male and female infants with respect to early vocalization. Aside from possible sex differences in the significance of vocalization, it is to be noted that both vocalization and fixation time displayed better stability from 8 to 13 months among girls than among boys.
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From page 344... ...
Bell. A facial dimension in visual discrimination by human infants.
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Language and intelligence: a longitudinal study of the first eight years.
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JEROME KAGAN DISCUSSION DR. KAGAN: I want to add to the first empiric generalization summarized in my paper, dealing with the changing control of fixation time in the young infant.
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From page 347... ...
Continuity in Cognitive Development During the First Year of Life We believe that tempo of play, like any behavior, is determined by multiple factors. Obviously, the richer the set of hypotheses the child has for a particular object, the longer he will play with it.
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From page 348... ...
JEROME KAGAN more commonly for the impulsive than for the reflective children. Only one type of error was more frequent for the reflective children.
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From page 349... ...
Continuity in Cognitive Development During the First Year of Life pect of a variable that has always been present in man's description of man. Hippocrates talked of the sanguine, choleric, and phlegmatic types, and Jung talked about introversion and extroversion.
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From page 350... ...
JEROME KAGAN used. To be specific, one of the patterns was a triangle inside a circle.
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From page 351... ...
The field of early perceptual development can be conveniently divided into four interrelated topics: visual-motor coordination and spatial localization, visual resolution and discrimination capacities, visual preferences and other selective responses to visual stimulation, and the retention of visual information and other effects of visual experience.
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From page 352... ...
Visual-motor coordination is the primary determinant of spatial localization and accurate directed responses, whereas visual discrimination capacity is the primary determinant of the intake of visual information, assisted by visual-motor coordination to the degree that it may exist. This distinction raises an issue of historical importance: By what response indicators shall visual perception be measured in the young infant?
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From page 353... ...
Until recently, these procedures were not thought to be applicable to the infant in the early months, owing to the lack of coordinated, visually directed responses, as well as to the lack of adequate learning abilities. But advances in technology have made feasible the conditioning even of newborn infants (see the following presentation, by Lipsitt)
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From page 354... ...
Vertical striped patterns of three widths were each paired with gray to determine the smallest pattern that would be discriminated from an unpatterned target, as a rough estimate of visual acuity.14 Listed next are three steps in a "complexity" dimension, using a series of white squares containing 0, 1, 4, or 16 black squares, regularly arranged. In the next three pairs, linear versus curvilinear forms or arrangement were opposed, but with white : black ratio and length of contour equated.
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From page 355... ...
Visual Perception and Experience in Infancy FIGURE 1 Visual-preference testing apparatus in mock operation. So that the baby could be seen in the picture, the crib was not set in as far as it would be in normal operation.
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From page 356... ...
Infants Showing Longer Fixation of Left or Right Stimulus of Pair6 Stimulus Targets Premature0 Full-termd Acuity gratings ^-in.-striped-gray 22-0 26-0 ^-in.-striped-gray 23-1 23-3 g-in.-striped-gray 13-7 10-11 Complexity pairings, no. of elements 0-1 2-27 3-24 1-4 18-9 15-11 4-16 20-7 16-8 Linear versus round configurations L1-R1 14-7 13-11 L2-R2 12-10 12-11 L3-R3 9-10 13-10 Other stimulus variations*
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From page 357... ...
For example, better visual acuity than hitherto found has been suggested for newborn infants by tests using both differential 357
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From page 358... ...
Without getting into the problem of defining "complexity" and distinguishing it from other variations in patterning, it can safely be stated that the young infant can discriminate more than one dimension of visual patterns. These various developmental changes in responsiveness to patterns might be explained by improvement in visual acuity, by an increase in the number and variety of discriminable dimensions of patterns, or by changes in the preferred points along the discriminated dimensions.
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From page 359... ...
Thus, some of the changes cannot be attributed to the development of visual capacities as such, and indicate, instead, the increased attention value of some patterns relative to others. Changes in visual selectivity may have as much portent for perceptual development in the infant and child as changes in visual acuity.
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From page 360... ...
Among the stimuli that have been used to date, infants during the early weeks of life have looked most at sharply defined patterns, especially black-and-white patterns. That was brought out most clearly in a longitudinal study designed for other purposes -- namely, to show differences in the rate of development of visual preferences between two selected groups of infants.12'13 The 18 pairs of stimulus targets (Figure 3)
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From page 361... ...
were also sharply defined patterns consisting of white elements against a blue background. By far the lowest in attention value was pair 18 (plain white and gray)
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From page 362... ...
After 2 months of age, high pattern definition was not sufficient, although some sharply defined patterns continued to receive long fixation times. Between 4 and 6 months, widely diverse targets were of high attention value; the topranking five were pair 7 (mesh and wood object versus rotating red-onyellow disk)
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From page 363... ...
I . I 4 8 12 16 20 24 28 32 36 40 44 48 52 AGE, WEEKS FIGURE 4 Fixation times for each target of a pair presented together for a total of 40 sec, averaged for the same 10 infants at each age.
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From page 364... ...
, the strong initial preference for a black-and-white schematic face pattern over a face photograph disappeared by 16 weeks of age, most likely owing to the decrease in the early attention value of sharply defined patterns and the subsequent interest in other, more subtle patterns -- as was true for pair 16. The irrelevance of the facial resemblance is suggested by an absence, in the lower graph, of preference for the correct over the scrambled arrangement of a schematic face until about 20 weeks of age; in fact, there was some early preference for the scrambled face.
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From page 365... ...
I . -L i I i l I L 4 8 12 16 20 24 28 32 36 40 44 48 52 AGE, WEEKS FIGURE 5 Fixation times for each target of a pair presented for a total of 40 sec, averaged for the same 10 infants at each age.
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From page 366... ...
ROBERT L FANTZ 35 25 15 _ PAIR 8 - Left target Right target < rr 35 25 15 PAIR 12 - Left target Right target I I I I I I J_ 52 8 12 16 20 24 28 32 AGE, WEEKS 36 40 44 48 FIGURE 6 Fixation times for each target of a pair presented for a total of 40 sec, averaged for the same 10 infants at each age.
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From page 367... ...
Familiar target Unfamiliar target -L -L -L 12 16 20 24 28 32 AGE, WEEKS 36 40 44 48 52 FIGURE 7 Fixation times for each target of a pair presented together for a total of 40 sec, averaged for the same 10 infants at each age. Targets (from Figure 3)
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From page 368... ...
Such results might well have been included under the heading of "visual experience." But they are equally relevant to visual selectivity, inasmuch as novelty is one category of stimulus determinant of differential attention -- one that happens to be of particular theoretical importance. Surprisingly, response to novelty has been quite difficult to measure reliably and predictably; it has been affected by seemingly minor variations in experimental conditions.8 One of the persistent problems is that of equating patterns in initial attention value, so that effects of recent exposures will not be obscured.
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From page 369... ...
To permit better comparison of the two groups, fixation times were converted to percentages of total fixation time given to the familiar pattern in successive testing weeks (Figure 8) ; 50% indicated chance response.
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From page 370... ...
For each group, fixation times for the two targets were converted to percentages for the target that had been repeatedly exposed earlier in the testing session, relative to the novel one. Percentages are based either on two 20-sec exposures (top graph)
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From page 371... ...
, I . i_ 8 10 12 14 WEEKS OF AGE 16 18 20 FIGURE 9 Results comparing selected home infants and institution infants on development of preference for circular over linear arrangement of line segments.
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From page 372... ...
These and other less clear-cut results indicate that tracing changes in visual selectivity within short exposures, as well as over weeks of age, is a promising approach to the problems of studying information processing and effects of visual exposure in the young infant. In the overall analysis of group differences, including the results given in Figures 8 and 9, the home group of infants showed significantly earlier or greater changes in preference for eight pairs of targets taken separately and for all 18 pairs averaged together.13 The significance of changes in visual selectivity as indicators of rate of perceptual-cognitive development is suggested by this differentiation between groups of infants with high expectation of eventual differences in cognitive performances, due to either congenital or early environmental differences.
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From page 373... ...
As in the case of studying visual capacities, the available approaches to studying experiential effects are limited by the slow motor development of the infant, with the additional problem of varying experience in acceptable but sufficiently controlled ways. Recently developed conditioning procedures (as described above)
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From page 374... ...
For varying experience in human infants, enrichment procedures must be substituted for visual deprivation, perhaps starting with infants who happen to be in a relatively stimulus-poor environment.29 In a recent unpublished study of institution-reared infants using this approach, we provided 10 weeks of extra patterned visual stimulation in the crib and nursery (including a merry-go-round of varied objects) for every other entering neonate.
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From page 375... ...
STA GES OF PER CEPTUAL DE VEL OPMENT In most of the research cited here, visual preferences have served as convenient behavioral indicators of the early development of visual perception and information processing. From another viewpoint, the visual selectivities themselves are part of the development process; they have considerable influence on what information is taken in for processing and for directing behavior.
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From page 376... ...
But in later months, the attention value of various patterns generally decreases, and attention turns more to solid objects, flashing lights, brightly colored objects, and moving targets (among the targets used to date)
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From page 377... ...
, whereas object solidity and form are highly relevant stimulus characteristics that were found to continue to be of high attention value throughout the first 6 months of life. This apparent development has also been shown to take place in infant monkeys,9 which in the early months of life without deprivation showed visual preferences for patterned over plain stimuli and for some patterns over others.
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From page 378... ...
(This is not intended to deny the complexities of learning to read, but merely to suggest that the untrained interest in patterns on paper may be one essential predisposing factor.) This is a new stage of information processing, rather than a reversion to the earlier visual exploration of patterns, for the child is now much more efficient and retentive in his explorations and gives meaning to much of the informational content of the patterns.
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From page 379... ...
Changes in visual selectivity may in fact be of more critical importance, in that the basic oculomotor coordinations, visual acuities, and pattern-discrimination capacities are present long before they are put to use in deciphering markings on paper. And if the new visual selectivities of the young child are necessary for facilitation of the normal development of pictorial perception and reading, then aberrations in the development of these selectivities could easily cause retarded development of these complex perceptual achievements; such a possibility is at least worth exploring.
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From page 380... ...
L Studying visual perception and the effects of visual exposure in early infancy.
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From page 381... ...
Rock. A reappraisal of the roles of past experience and innate organizing processes in visual perception.
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From page 382... ...
Newborn infants do indeed see, and they profit from, or appreciate, and process visual information in important ways -- i.e., their memories are affected by what they look at. Fantz's experiments, as 552
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From page 383... ...
PR EM A TURE INFANTS The easiest way to summarize the Miranda data, without distorting the essential results, is to say that 1 month before the expected date of birth, but 3 weeks after birth, the premature babies' pattern preferences were essentially consonant with the visual-fixation behavior displayed by the full-term newborn babies tested at a mean age of 3l/2 days. In general, both the premature and the full-term babies resolved grating stimuli of 1/2 in.
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From page 384... ...
Kagan's presentation does not leave the impression that habituation and learning processes do not occur in the human infant until he is 30, 60, or 90 days old. A growing body of data indicates that newborn children are remarkable habituators to stimulation of many sorts.
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From page 385... ...
Once the newborn child is habituated to a given odorant or tone, presentation of a different stimulus without violation of the temporal FIGURE 1 Awake and alert newborn being administered an odorant on cotton swab.
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From page 386... ...
REINFORCEMENT Kagan's inclination, I think, is toward the view that a child does not become a habituator or learner until perhaps 30-60 days of age. Studies of newborn children show that they learn; the best evidence comes from a series of studies in which Dr.
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From page 387... ...
Many mothers report that they are able to communicate with their newborn babies best while they are feeding them. The child looks up at its mother's eyes, and while sucking looks around at the corners of the room and at other interesting objects in the environment.
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From page 388... ...
In speaking to nurses with considerable experience with newborn babies, I have often been amazed, in view of their extensive opportunities to observe infants, that many do not believe that newborn babies can see. When we invite them into our laboratory and show them newborn babies' horizontal and vertical scanning of dangling objects, they are often overwhelmed and begin to wonder about their own visual perception.
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From page 389... ...
The apparatus would be suitable for the study of visual exploration in infants, although we have not used it that way. When we went to work in the infant home, we discovered that the nuns had suspended mobiles over the cribs of infants as young as 5 days of age.
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From page 390... ...
I submit that visual reinforcement in real life is more like that, and not so much like pellet reinforcement. We implemented research involving visual reinforcement of the hangingmobile type, in which the child controls his own visual input from his surroundings.
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From page 391... ...
This was followed by a 15-min conjugate reinforcement phase. The effect of this reinforcement on the babies' activity levels was highly significant.
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From page 392... ...
RE-EXT. FIGURE 5 Mean response rate as a function of conjugate reinforcement condition over 46 min of continuous observation in four infants from previous group; leg attached to mobile during acquisition.
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From page 393... ...
There was recovery of the conjugate reinforcement effect, and if the subject's limb was released from control of the mobile, his activity then declined. That the infants could be shown to intensify their behavior when in control of their own stimulus input and to reduce their behavior when the response was no longer pertinent to visual input indicates that lively visual stimulation may serve as a reinforcer to enhance learning 393
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From page 394... ...
I6, 1967 BASELINE CONDITIONING EXTINCTION RECONDITIONING EXTINCTION RECONDITIONING EXTINCTION SUCCESSIVE 30 SECOND INTERVALS FIGURE 7 Unpublished data of Smith and Lipsitt. In third training session, infant's right leg responses activated the mobile during conditioning periods.
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From page 395... ...
Conjugate Reinforcing with Sucking We are also seeing infants at various ages in the Hunter Laboratory for conjugate reinforcement experiments devised and conducted by Professor Siqueland. In these experiments, the child controls his visual input through his sucking behavior.
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From page 396... ...
Another group was a baseline group, which received no visual stimulation for sucking; the babies had pacifiers in their mouths and their sucking behavior was recorded, but the sucking did not control the visual feedback. A third group, represented by the dashed line that begins at the bottom, got reinforcement withdrawal with increases in sucking; that is, this group started with the visual stimulus already full on, and successive or repetitive sucking on the device produced withdrawal or CONJUGATE REINFORCEMENT RED AND WHITE BIRDS 5 70 DAYS OLD' SESSION 6 NOV.
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From page 397... ...
diminution of illumination of the visual stimulus commensurate with the high-amplitude sucking. These children, 4 months old, were being operantly reinforced for their sucking behavior, and the behavior was controlled by the "novelty" and attractiveness of the stimulus.
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From page 398... ...
One group received visual reinforcement; the sucking behavior of a second group was associated with stimulus diminution; and a third group served as a control, with no visual changes occurring during the recording of sucking behavior.
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From page 399... ...
When the stimulated twins are now tested in the controlled learning situation, those who have had such training seem on the basis of preliminary findings to learn faster in this conjugate reinforcement situation. The stimulated and nonstimulated premature babies are tested "blind" by an assistant who does not know whether they are stimulated or control subjects.
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From page 400... ...
It should be apparent that very young infants do indeed learn. It should also be obvious from our conjugate reinforcement data that infants are captivated by visual stimulation, particularly if it is novel.
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From page 401... ...
Pretraining with visual stimulation of the sort that I have described here, perhaps along with coordinated auditory stimulation such as occurs in real life, must be exceedingly important in the development of fascination with reading materials on the part of children who read well and who like to read. It is my belief that children who read well and who read a lot find some sort of joy in reading -- joy in controlling their own environment -- very much as the children in the conjugate reinforcement situation seem to enjoy manipulating their own visual input.
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From page 402... ...
Conjugate reinforcement of infant exploratory behavior.
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Key Terms
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