Perceptual and Motor Skills, 1978,47,699-706.
@ Perceptual and Motor Skills 1978
DYSLEXIA, AN IMBALANCE I N CEREBRAL INFORMATIONPROCESSING STRATEGIES1 P. G. AARON Itzdiancr State University Summary.-Reading ability seems to involve analytic-sequential processing of selected letters and a holistic-simultaneous perception of the salient features of the entire word. The dyslexic child, being normal in intelligence, is most likely deficient in either one of the two processes while being normal in the other. T o test this hypothesis, 28 reading disabled children, on the basis of the nature of errors made in a writing from dictation task, were divided into two groups: analytic-sequential deficient and holistic-simultaneous deficient. Further tesring showed that the first group was poor in processing a sequence of digits but normal on holistic-simultaneous memory tasks. The opposite pattern of performance was shown by the second group. A control group of 14 normal readers did not show such an imbalance.
The present report provides some experimental support to the view that specific reading disability (dyslexia) in children is either due to deficiency in the analytic-sequential processing of information or deficiency in the holisticsimultaneoi~sprocessing of information, believed to be mediated predominantly. by the left and right ceiebral hemispheres, respectively. Analytic-sequential and holistic-simultaneous operations seem to be two fundamental information-processing strategies of human beings (Das, 1973; Bever, 1975). This statement seems equally applicable to the reading process as well, the decoding aspect of which involves at least two similar operations, viz., sequential processing of a selected sample of a series of letters in a word and the Gestalt-simultaneous processing of the salient feature of the word itself. Information from four different classes of population supports this conclusion: normal readers, stroke patients, blind subjects who read the braille, and reading-disabled children. After reviewing a number of studies of normal readers, Smith and Holrnes ( 1971) have concluded that in reading, the domain of word categories is distinguished separately from that of the letters and that letter identification and word identification are two independent operations. Reports of stroke patients who could name individual letters but could not read whole words and vice versa (Kinsbourne & Warrington, 1962a, 1962b; Albert, et al., 1973; Hecaen & Kremin, 1976) depending upon the location of the lesion, demonstrate that these two processes are dissociable. Subjective reports by blind subjects show that maximum efficiency in reading the braille is achieved when the fingers of both hands are used simultaneously thus sending information to both T h i s srudy was supported by a grant from the Research Committee of Indiana State University, Terre Haute, Indiana. Requests for reprints should be sent to: P. G. Aaron, Professor of Educational Psychology, 1506, Statesman Towers, Indiana State University, Terre Haute, IN 47809.
700
P. G . AARON
hemispheres (Smith, 1929). These observations indicate that both sequential and holistic operations are involved in the reading process. It can be concluded that deficiency in the analytic-sequential or the holistic-simultaneous process could impair reading ability and may result in two different clinical forms of dyslexia. Boder's (1971, 1973) classification of dyslexics into dysphonetics and dyseidetics is based on such a view. It was hypothesized, therefore, that in a group of randomly selected dyslexic children, some will be inefficient in the analytic-sequential processing ability but normal in the holistic-simultaneous processing ability; others will be deficient in the holistic-simultaneous process but normal in the analytic-sequential process. Normal readers, on the other hand, will be competent in both processes. The strategy involved in the testing of this hypothesis was to classify dyslexic children into two categories, dysphonetics (analytic-sequential deficient) and dyseidetics (holistic-simultaneous deficient), and to determine if these deficiencies reflect a corresponding imbalance in information-processing strategies.
METHOD Szlbjects Classification of dyslexic children into analytic-sequential deficient (dysphonetic) and holistic-simultaneous deficient (dyseidetic) was accomplished with the aid of Boder's diagnostic screening procedure (1973). Boder's procedure involves the administration of a word-reading inventory of graded difficulty and, on the basis of the subject's performance, asking him to write from dictation five words from among those he had been able to read without hesitation (sight vocabulary) and five words which he had read with difficulty (unknown vocab ulary). According to Boder, the dysphonetic child whose auditory memory for analytic-sequential processes is poor depends on visual Gestalts and has a reasonably good memory for the over-all word image. H e is, nevertheless, poor in remembering the sequential order of elements within a word. Consequently he omits, reverses, or displaces letters. In the writing to dictation task he, therefore, makes bizarre mistakes by writing "koo" for "book" or "faete" for "father." O n the other hand, the dyseidetic child whose visual memory for words is poor depends heavily on sequential auditory memory and tends to write "tebl" for "table" or "maek for "make," the way words sound rather than how they look. This diagnostic screening procedure, therefore, provides a simple means of identifying the two groups of dyslexic children. Boder's diagnostic screening test was administered to a group of 46 reading disabled children from Grades 2, 3, and 4. As determined by the Primary Mental Ability test of intelligence, these children had a mean IQ of 94.2, were free from any noticeable psychological or neurological impairments, and were reading more than one grade lwel below expectation. As judged by their teachers they were also not impaired in the oral expressive aspects of language. Following the
DYSLEXIA
701
specific procedures recommended by Boder (1973), the subjects were classified as dysphonetic or dyseidetic on the basis of the nature of their spelling errors (Figs. 1 and 2 ) . Only children who could be clearly identified as dysphonetic or dyseidetic were selected for this study. After this initial screening, an attempt was made to match each child in one group with another child from the other group on the basis of their CA, MA, and sex. Such a matching resulted in 14 pairs of subjects. The dyseidetic and dysphonetic groups did not differ from each other in CA, MA, or reading scores (Table 1) . Another matched group of 14 normal readers was also selected to serve as the control group. The reading score of the control group was significantly different from that of the two dyslexic groups. There were 11 boys and 3 girls in each group.
FIG. 1. Specimen writing of an analytic-sequential deficient child
FIG. 2. Specimen writing of a holisticsimultaneous deficient child
Matekh Four tests were administered to all the three groups. A Kodak Carousel projector with a rear-view screen and timer was used for Tests 1, 3, and 4. ( 1 ) M e m o ~ yfor faces.-A set of 25 photographs of men and women taken from a college yearbook was made into photographic slides. The photographs were selected with care to eliminate any readily distinguishable feature such as moustache, hair style, or dress. Each of the 25 slides was shown to each subject on a rear-view screen for 5 sec. The intertrial interval was about 1 sec. After
702
P. G. AARON
the exposure of all the 25 slides, a multiple-choice test, in which three other similar looking faces appeared simultaneously dong with each original piccure, was administered. The subject had to identify correctly the face he had seen before. Since human faces cannot be readily verbalized, it was expected that those children who are dyseidetic would correctly identify significantly fewer photographs than the dysphonetic children. ( 2 ) WISC Digit Span.-This test of auditory-sequential memory was administered to all children and the memory for the sequence of both forward and backward digits was noted. Since this task tests the ability to process information sequentially, it was expected that the dyseidetic children would obtain higher scores than the dysphonetic children in this task. ( 3 ) Reprodaction of paired letter stima1i.-In this task 16 paired letter stimuli were used. The construction of these stimuli involved placing two letters such as d and b close to each other with a very fine dividing line between them and photographing them in order to make projection slides. When projected, the stimuli appeared to have almost no space berween the letters. During testing, each stimulus was projected on the screen for a period of 2 sec. and the subject was asked to reproduce on a piece of paper what he had seen. These stimuli were designed in such a way that each stimulus could be reproduced as a letter and its reversed form or as a single visual gestalt. For example, the stimuli db and HH could be processed analytically and sequentially as d and b and H and H or as single visual gestalts:
It was assumed that the written response would adequately reflect the information-processing strategy of the subject and that the dysphonetic child would process them as a single gestalt whereas the dyseidetic subject would process them as two discrete letters (Figs. 3 and 4 ) . ( 4 ) Reproduction of individmzl lettm/shapes.-Individual letters and unfamiliar geometrical shapes were also photographed and made into slides. Sixteen such slides were prepared and each slide was exposed under two different recall conditions. Under immediate recall, the stimulus was exposed for 1/2 sec. and the subject was asked to reproduce immediately on a piece of paper what he had seen. The next stimulus appeared on the screen soon after the subject had finished writing. Under delayed recall, the same set of slides, rearranged in a different order, was exposed for 1/2 sec. Immediately following the presentation of each stimulus the experimenter read aloud a series of three digits (if the stimulus was a letter) or three letters (if the stimulus was a shape) and the subject was asked to repeat it. This interpolated task took approximately 5 sec. Following this delay, the subject was asked to reproduce on a sheet of paper what
DYSLEXIA
FIG. 3. Reproduction of the paired
FIG.4. Reproduction of the paired
letter stimuli by an analytic-sequential deficient (dysphonetic) child
letter stimuli by a holistic-simultaneous deficient (dyseidetic) child
he had seen on the screen. When the subject had finished writing, the next stimulus appeared on the screen. The task was aimed to srudy the tendency of some young children to reverse or rotate letters when they write. It is known that human beings generally process pictures and shapes without regard to their left-right orientation along the horizontal axis (Standing, et al., 1970). Consequently, i t was expected that children such as the dysphonetics who process the stimulus as a picture, very much like a gestalt, are likely to disregard the left-right orientation and produce more reversals than children who process it as sequential units. Administering the task under two different recall conditions was to see if such reversal is primarily a perceptual or memory phenomenon. RESULTSAND DISCUSSION The results of the four tests are shown in Table 1. Four statisrically reliable findings emerged. ( 1) The dysphonetic group identified significantly more faces than the dyseidetic group did. The performance of the dysphonetic group in this task was comparable to that of the control group. ( 2 ) The dyseidetic group recalled more sequence of digits than the dysphonetic group did even though the difference between the means did not reach the conventional level of statistical significance ( p < . l o ) . The number of digits recalled by the dysphonetic group, however, was significantly lower than that of the control group. ( 3 ) The dysphonetic group reproduced significantly more paired letters
704
P. G. AARON
TABLB
1
MEANSCORES OBTAINED BY DYSLEXIC GROUPS AND CONTROLS ( n= ~ 14)
Groups Dyspho- Dyseinetic detic Age MA (yr.)
F
Control
1, 2, vs 3
0.17 0.30 27.43t
1
2
3
9.07 8.37 2.12 12.57 1.60
9.17 8.75 2.37 10.07 8.34
8.86 8.85 4.00 13.29 9.14
0.07
Reading (grade) * Memory for faces Digic Span Letter reversals (no delay) 0.15 Letter reversals (5-sec. delay) 0.79 Gestalts reproduced in Paired Letters Test 2.58 *Gates-McGinirieReading Test. t p 5 . 0 2 . $ p 4.001.
Group Comparisons: t 1 vs 2 1 vs 3 2 vs 3
1.01 2.12t 1.62
2.40t 0.56 4.16f
2.07t 2.80$ 1.29
0.07
0.45
0.45
0.15
0.07
2.06t
6.23$
0.75
0.71
0.64
2.13t
2.08t
0.81
as visual gestalts than the other two groups did. ( 4 ) The dysphonetic group reversed more letters and shapes than the other groups under delayed recall. Under immediate recall, there was no significant difference in reversals among the three groups. A majority of children even in the analytic-sequential deficient group did not reverse letters under either condition of recall. These results indicate that dyslexic children deficient in one informationprocessing strategy are normal in the other process and thus lead to the confirmation of the hypothesis proposed earlier. Such an anomalous development wherein one or the other function predominates has also been reported for auditory functions in younger dyslexics (Bakker, et al., 1973), for visual functions in older dyslexics (Yeni-Komshian, et dl., 1975), and for motor skills in learning disabled children (Rudel, 1974). In a group of dyslexics, Syrnmes and Rapoport (1972) as well as Witelson (1976) found superior spatial visualization and a corresponding inferiority in sequencing. Several studies show that adult humans can recognize a picture or a geometrical shape as familiar even if it is the left-right mirror image of the one seen before and they cannot tell if it is the original or not (Bartlett, 1932; Standing, et al., 1970; Rock, 1973). Thus, right-left direction along the horizontal axis is not a crucial feature in the processing of visual gestalts. In the present study, significantly more letters were reversed by some children in the dysphonetic group indicating that they tend to process letters as though they are pictures rather than phonetic units. This cognitive strategy could account for the high frequency of reversals and rotations of letters reported for dyslexic children. Further, the fact that such reversals were made only under delayed recall is consistent with the findin8s of other investigators (Morrison, et al., 1977) and
DYSLEXIA
705
indicates that letter reversal is primarily a storage-retrieval rather than a perceptual problem. The dyseidetic children showed fewer rotations but ~roducedmore mutilated letters and shapes than the dysphonetic group even though the difference was nonsignificant ( p < .lo). The visual-perceptual problems encountered by some disabled readers in reproducing geometric forms could be explained in terms of their tendency to process such stimuli analytically as verbal units rather than as visual gestalts. Some Clinical Implications ( 1 ) Dyslexia, when seen in children with no previous adverse health history, seems to be the result of an imbalance in the information-processing strategies. ( 2 ) Since dyslexics seem to be normal or above normal in certain cognitive abilities, such strength may be taken advantage of while devising remedial programs. There is some evidence2 to support such a view. ( 3 ) Letter reversals, so often held symptomatic of dyslexia in children, may not be associated with any visual perceptual deficit. In fact, such children seem to have normal visual-memory capabilities. Furthermore, since very few dyslexic children show a consistent tendency for reversals, letter disorientation in writing is of questionable diagnostic value. (4) The present study indicates that Boder's diagnostic screening procedure is a valid but simple means of differentiating the two clinical subtypes of dyslexia. REFERENCES ALBERT,M. L., YAMADORI,A., GARDNER,H., & HOWES, D. Comprehension in alexia. Brain, 1973, 96, 317-328. BAKKER,D. J., SMINK, T., & REITSMA,P. Ear dominance and reading ability. Costex, 1973. 9. 301-312. B A R T L E ~R. , C. Remembering: a study in experimental and ~ o c dpsychology. Cambridge: Cambridge Univer. Press, 1932. BEVER,T. G. Cerebral asymmetries in humans are due to differentiation of two incompatible processes: holistic and analytic. Ann& of the New York Academy of Sciences, 1975, 263, 251-262. BODER,E. Developmental dyslexia: prevailing diagnostic concepts and a new diagnostic approach. In H . R. Myklebust (Ed.), Progress in learning disabilities. New York: Grune & Stratton, 1971. Vol. 2. Pp. 293-312. BODER.E. Developmental dyslexia: a diagnostic approach based on three atypical reading -spelling patterns. Developmental Medicine and Child Neurology, 1973, 15, 663-687. DAS, J. P. Structure of cognitive abilities: evidence for simultaneous and successive processing. Jorcrnal of Educational Psychology, 1973, 65, 1083-108. HECAEN,G., & KREMIN,H. Neurolinguistic research on reading disorders resulting from left hemisphere lesions: aphasic and "pure" alexia. In H. Whitaker & H. A. Whitaker (Eds.), Studies in nerrrolingrristics. Vol. 2. New York: Academic Press, 1976. Pp. 269-329. KINSBOURNE, M., & WARRINGTON,E. A disorder of simultaneous form perception. Brain, 1962, 85, 461-486. ( a ) 'P. G. Aaron, S. L. Grantham, & N. Campbell, Differential treatment of dyslexia of diverse etiologies. (Unpublished paper)
706
P. G.AARON
KINSBOURNE,M., & WARRINGTON,E. A variety of reading disability associated with righc hemisphere lesions. Journal o f Neurology, Netnosurgery amd Psychiatry. 1962, 25, 339-344. ( b ) MORRISON,F. J., GIORDANI, B., & NAGY, J. Reading disability: an information processing analysis. Science, 1977, 196, 77-79. ROCK, I. Orientation and form. New York: Academic Press, 1973. RUDEL,R. G. The neurolog,ical assessment of learning disabilities. In S. G. Brainard ( E d . ) , Learning disa zlztres: zssues and recornmendations for research. Washington, D. C.: 1974. Pp. 123-141. (N.I.E. Conference Report, U. S. Department of HEW) SMITH,F., & HOLMES,L. D. The independence of letter, word and meaning identification in reading. Reading Research Quarterly, 1971, 6, 394-415. SMITH, M. J. Which hand is the eye of the blind? Genetic Prychology Monographs. 1929. 5. 209-252. STANDING,L., CONEZIO,J., & HABBR,R. Perception and memory for pictures: single trial learning of 2500 visual stimuli. Psychonomic Science, 1970, 15, 73-84. SYMMES,S. J., & RAPOPORT,L. J. Unexpected reading failure. (American Jownul o f Orthopsychirrtry, 1972, 42, 82-91. WITELSON,F. S. Abnormal righc hemisphere specialization in developmental dyslexia. In M. R. Knights & D. J. Bakker (Eds.). T h e newropsychology of learning diso+derr. Baltimore: Univer. Park Press, 1976. Pp. 233-255. YENI-KOMSHIAN,H. G.,ISENBBRG, D., & GOLDBERG, H. Cerebral dominance and reading disability: left visual field deficits in poor readers. Neuropsychologia, 1975, 13.83-93. Accepted August 17, 1978.
@ Perceptual and Motor Skills 1978
DYSLEXIA, AN IMBALANCE I N CEREBRAL INFORMATIONPROCESSING STRATEGIES1 P. G. AARON Itzdiancr State University Summary.-Reading ability seems to involve analytic-sequential processing of selected letters and a holistic-simultaneous perception of the salient features of the entire word. The dyslexic child, being normal in intelligence, is most likely deficient in either one of the two processes while being normal in the other. T o test this hypothesis, 28 reading disabled children, on the basis of the nature of errors made in a writing from dictation task, were divided into two groups: analytic-sequential deficient and holistic-simultaneous deficient. Further tesring showed that the first group was poor in processing a sequence of digits but normal on holistic-simultaneous memory tasks. The opposite pattern of performance was shown by the second group. A control group of 14 normal readers did not show such an imbalance.
The present report provides some experimental support to the view that specific reading disability (dyslexia) in children is either due to deficiency in the analytic-sequential processing of information or deficiency in the holisticsimultaneoi~sprocessing of information, believed to be mediated predominantly. by the left and right ceiebral hemispheres, respectively. Analytic-sequential and holistic-simultaneous operations seem to be two fundamental information-processing strategies of human beings (Das, 1973; Bever, 1975). This statement seems equally applicable to the reading process as well, the decoding aspect of which involves at least two similar operations, viz., sequential processing of a selected sample of a series of letters in a word and the Gestalt-simultaneous processing of the salient feature of the word itself. Information from four different classes of population supports this conclusion: normal readers, stroke patients, blind subjects who read the braille, and reading-disabled children. After reviewing a number of studies of normal readers, Smith and Holrnes ( 1971) have concluded that in reading, the domain of word categories is distinguished separately from that of the letters and that letter identification and word identification are two independent operations. Reports of stroke patients who could name individual letters but could not read whole words and vice versa (Kinsbourne & Warrington, 1962a, 1962b; Albert, et al., 1973; Hecaen & Kremin, 1976) depending upon the location of the lesion, demonstrate that these two processes are dissociable. Subjective reports by blind subjects show that maximum efficiency in reading the braille is achieved when the fingers of both hands are used simultaneously thus sending information to both T h i s srudy was supported by a grant from the Research Committee of Indiana State University, Terre Haute, Indiana. Requests for reprints should be sent to: P. G. Aaron, Professor of Educational Psychology, 1506, Statesman Towers, Indiana State University, Terre Haute, IN 47809.
700
P. G . AARON
hemispheres (Smith, 1929). These observations indicate that both sequential and holistic operations are involved in the reading process. It can be concluded that deficiency in the analytic-sequential or the holistic-simultaneous process could impair reading ability and may result in two different clinical forms of dyslexia. Boder's (1971, 1973) classification of dyslexics into dysphonetics and dyseidetics is based on such a view. It was hypothesized, therefore, that in a group of randomly selected dyslexic children, some will be inefficient in the analytic-sequential processing ability but normal in the holistic-simultaneous processing ability; others will be deficient in the holistic-simultaneous process but normal in the analytic-sequential process. Normal readers, on the other hand, will be competent in both processes. The strategy involved in the testing of this hypothesis was to classify dyslexic children into two categories, dysphonetics (analytic-sequential deficient) and dyseidetics (holistic-simultaneous deficient), and to determine if these deficiencies reflect a corresponding imbalance in information-processing strategies.
METHOD Szlbjects Classification of dyslexic children into analytic-sequential deficient (dysphonetic) and holistic-simultaneous deficient (dyseidetic) was accomplished with the aid of Boder's diagnostic screening procedure (1973). Boder's procedure involves the administration of a word-reading inventory of graded difficulty and, on the basis of the subject's performance, asking him to write from dictation five words from among those he had been able to read without hesitation (sight vocabulary) and five words which he had read with difficulty (unknown vocab ulary). According to Boder, the dysphonetic child whose auditory memory for analytic-sequential processes is poor depends on visual Gestalts and has a reasonably good memory for the over-all word image. H e is, nevertheless, poor in remembering the sequential order of elements within a word. Consequently he omits, reverses, or displaces letters. In the writing to dictation task he, therefore, makes bizarre mistakes by writing "koo" for "book" or "faete" for "father." O n the other hand, the dyseidetic child whose visual memory for words is poor depends heavily on sequential auditory memory and tends to write "tebl" for "table" or "maek for "make," the way words sound rather than how they look. This diagnostic screening procedure, therefore, provides a simple means of identifying the two groups of dyslexic children. Boder's diagnostic screening test was administered to a group of 46 reading disabled children from Grades 2, 3, and 4. As determined by the Primary Mental Ability test of intelligence, these children had a mean IQ of 94.2, were free from any noticeable psychological or neurological impairments, and were reading more than one grade lwel below expectation. As judged by their teachers they were also not impaired in the oral expressive aspects of language. Following the
DYSLEXIA
701
specific procedures recommended by Boder (1973), the subjects were classified as dysphonetic or dyseidetic on the basis of the nature of their spelling errors (Figs. 1 and 2 ) . Only children who could be clearly identified as dysphonetic or dyseidetic were selected for this study. After this initial screening, an attempt was made to match each child in one group with another child from the other group on the basis of their CA, MA, and sex. Such a matching resulted in 14 pairs of subjects. The dyseidetic and dysphonetic groups did not differ from each other in CA, MA, or reading scores (Table 1) . Another matched group of 14 normal readers was also selected to serve as the control group. The reading score of the control group was significantly different from that of the two dyslexic groups. There were 11 boys and 3 girls in each group.
FIG. 1. Specimen writing of an analytic-sequential deficient child
FIG. 2. Specimen writing of a holisticsimultaneous deficient child
Matekh Four tests were administered to all the three groups. A Kodak Carousel projector with a rear-view screen and timer was used for Tests 1, 3, and 4. ( 1 ) M e m o ~ yfor faces.-A set of 25 photographs of men and women taken from a college yearbook was made into photographic slides. The photographs were selected with care to eliminate any readily distinguishable feature such as moustache, hair style, or dress. Each of the 25 slides was shown to each subject on a rear-view screen for 5 sec. The intertrial interval was about 1 sec. After
702
P. G. AARON
the exposure of all the 25 slides, a multiple-choice test, in which three other similar looking faces appeared simultaneously dong with each original piccure, was administered. The subject had to identify correctly the face he had seen before. Since human faces cannot be readily verbalized, it was expected that those children who are dyseidetic would correctly identify significantly fewer photographs than the dysphonetic children. ( 2 ) WISC Digit Span.-This test of auditory-sequential memory was administered to all children and the memory for the sequence of both forward and backward digits was noted. Since this task tests the ability to process information sequentially, it was expected that the dyseidetic children would obtain higher scores than the dysphonetic children in this task. ( 3 ) Reprodaction of paired letter stima1i.-In this task 16 paired letter stimuli were used. The construction of these stimuli involved placing two letters such as d and b close to each other with a very fine dividing line between them and photographing them in order to make projection slides. When projected, the stimuli appeared to have almost no space berween the letters. During testing, each stimulus was projected on the screen for a period of 2 sec. and the subject was asked to reproduce on a piece of paper what he had seen. These stimuli were designed in such a way that each stimulus could be reproduced as a letter and its reversed form or as a single visual gestalt. For example, the stimuli db and HH could be processed analytically and sequentially as d and b and H and H or as single visual gestalts:
It was assumed that the written response would adequately reflect the information-processing strategy of the subject and that the dysphonetic child would process them as a single gestalt whereas the dyseidetic subject would process them as two discrete letters (Figs. 3 and 4 ) . ( 4 ) Reproduction of individmzl lettm/shapes.-Individual letters and unfamiliar geometrical shapes were also photographed and made into slides. Sixteen such slides were prepared and each slide was exposed under two different recall conditions. Under immediate recall, the stimulus was exposed for 1/2 sec. and the subject was asked to reproduce immediately on a piece of paper what he had seen. The next stimulus appeared on the screen soon after the subject had finished writing. Under delayed recall, the same set of slides, rearranged in a different order, was exposed for 1/2 sec. Immediately following the presentation of each stimulus the experimenter read aloud a series of three digits (if the stimulus was a letter) or three letters (if the stimulus was a shape) and the subject was asked to repeat it. This interpolated task took approximately 5 sec. Following this delay, the subject was asked to reproduce on a sheet of paper what
DYSLEXIA
FIG. 3. Reproduction of the paired
FIG.4. Reproduction of the paired
letter stimuli by an analytic-sequential deficient (dysphonetic) child
letter stimuli by a holistic-simultaneous deficient (dyseidetic) child
he had seen on the screen. When the subject had finished writing, the next stimulus appeared on the screen. The task was aimed to srudy the tendency of some young children to reverse or rotate letters when they write. It is known that human beings generally process pictures and shapes without regard to their left-right orientation along the horizontal axis (Standing, et al., 1970). Consequently, i t was expected that children such as the dysphonetics who process the stimulus as a picture, very much like a gestalt, are likely to disregard the left-right orientation and produce more reversals than children who process it as sequential units. Administering the task under two different recall conditions was to see if such reversal is primarily a perceptual or memory phenomenon. RESULTSAND DISCUSSION The results of the four tests are shown in Table 1. Four statisrically reliable findings emerged. ( 1) The dysphonetic group identified significantly more faces than the dyseidetic group did. The performance of the dysphonetic group in this task was comparable to that of the control group. ( 2 ) The dyseidetic group recalled more sequence of digits than the dysphonetic group did even though the difference between the means did not reach the conventional level of statistical significance ( p < . l o ) . The number of digits recalled by the dysphonetic group, however, was significantly lower than that of the control group. ( 3 ) The dysphonetic group reproduced significantly more paired letters
704
P. G. AARON
TABLB
1
MEANSCORES OBTAINED BY DYSLEXIC GROUPS AND CONTROLS ( n= ~ 14)
Groups Dyspho- Dyseinetic detic Age MA (yr.)
F
Control
1, 2, vs 3
0.17 0.30 27.43t
1
2
3
9.07 8.37 2.12 12.57 1.60
9.17 8.75 2.37 10.07 8.34
8.86 8.85 4.00 13.29 9.14
0.07
Reading (grade) * Memory for faces Digic Span Letter reversals (no delay) 0.15 Letter reversals (5-sec. delay) 0.79 Gestalts reproduced in Paired Letters Test 2.58 *Gates-McGinirieReading Test. t p 5 . 0 2 . $ p 4.001.
Group Comparisons: t 1 vs 2 1 vs 3 2 vs 3
1.01 2.12t 1.62
2.40t 0.56 4.16f
2.07t 2.80$ 1.29
0.07
0.45
0.45
0.15
0.07
2.06t
6.23$
0.75
0.71
0.64
2.13t
2.08t
0.81
as visual gestalts than the other two groups did. ( 4 ) The dysphonetic group reversed more letters and shapes than the other groups under delayed recall. Under immediate recall, there was no significant difference in reversals among the three groups. A majority of children even in the analytic-sequential deficient group did not reverse letters under either condition of recall. These results indicate that dyslexic children deficient in one informationprocessing strategy are normal in the other process and thus lead to the confirmation of the hypothesis proposed earlier. Such an anomalous development wherein one or the other function predominates has also been reported for auditory functions in younger dyslexics (Bakker, et al., 1973), for visual functions in older dyslexics (Yeni-Komshian, et dl., 1975), and for motor skills in learning disabled children (Rudel, 1974). In a group of dyslexics, Syrnmes and Rapoport (1972) as well as Witelson (1976) found superior spatial visualization and a corresponding inferiority in sequencing. Several studies show that adult humans can recognize a picture or a geometrical shape as familiar even if it is the left-right mirror image of the one seen before and they cannot tell if it is the original or not (Bartlett, 1932; Standing, et al., 1970; Rock, 1973). Thus, right-left direction along the horizontal axis is not a crucial feature in the processing of visual gestalts. In the present study, significantly more letters were reversed by some children in the dysphonetic group indicating that they tend to process letters as though they are pictures rather than phonetic units. This cognitive strategy could account for the high frequency of reversals and rotations of letters reported for dyslexic children. Further, the fact that such reversals were made only under delayed recall is consistent with the findin8s of other investigators (Morrison, et al., 1977) and
DYSLEXIA
705
indicates that letter reversal is primarily a storage-retrieval rather than a perceptual problem. The dyseidetic children showed fewer rotations but ~roducedmore mutilated letters and shapes than the dysphonetic group even though the difference was nonsignificant ( p < .lo). The visual-perceptual problems encountered by some disabled readers in reproducing geometric forms could be explained in terms of their tendency to process such stimuli analytically as verbal units rather than as visual gestalts. Some Clinical Implications ( 1 ) Dyslexia, when seen in children with no previous adverse health history, seems to be the result of an imbalance in the information-processing strategies. ( 2 ) Since dyslexics seem to be normal or above normal in certain cognitive abilities, such strength may be taken advantage of while devising remedial programs. There is some evidence2 to support such a view. ( 3 ) Letter reversals, so often held symptomatic of dyslexia in children, may not be associated with any visual perceptual deficit. In fact, such children seem to have normal visual-memory capabilities. Furthermore, since very few dyslexic children show a consistent tendency for reversals, letter disorientation in writing is of questionable diagnostic value. (4) The present study indicates that Boder's diagnostic screening procedure is a valid but simple means of differentiating the two clinical subtypes of dyslexia. REFERENCES ALBERT,M. L., YAMADORI,A., GARDNER,H., & HOWES, D. Comprehension in alexia. Brain, 1973, 96, 317-328. BAKKER,D. J., SMINK, T., & REITSMA,P. Ear dominance and reading ability. Costex, 1973. 9. 301-312. B A R T L E ~R. , C. Remembering: a study in experimental and ~ o c dpsychology. Cambridge: Cambridge Univer. Press, 1932. BEVER,T. G. Cerebral asymmetries in humans are due to differentiation of two incompatible processes: holistic and analytic. Ann& of the New York Academy of Sciences, 1975, 263, 251-262. BODER,E. Developmental dyslexia: prevailing diagnostic concepts and a new diagnostic approach. In H . R. Myklebust (Ed.), Progress in learning disabilities. New York: Grune & Stratton, 1971. Vol. 2. Pp. 293-312. BODER.E. Developmental dyslexia: a diagnostic approach based on three atypical reading -spelling patterns. Developmental Medicine and Child Neurology, 1973, 15, 663-687. DAS, J. P. Structure of cognitive abilities: evidence for simultaneous and successive processing. Jorcrnal of Educational Psychology, 1973, 65, 1083-108. HECAEN,G., & KREMIN,H. Neurolinguistic research on reading disorders resulting from left hemisphere lesions: aphasic and "pure" alexia. In H. Whitaker & H. A. Whitaker (Eds.), Studies in nerrrolingrristics. Vol. 2. New York: Academic Press, 1976. Pp. 269-329. KINSBOURNE, M., & WARRINGTON,E. A disorder of simultaneous form perception. Brain, 1962, 85, 461-486. ( a ) 'P. G. Aaron, S. L. Grantham, & N. Campbell, Differential treatment of dyslexia of diverse etiologies. (Unpublished paper)
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KINSBOURNE,M., & WARRINGTON,E. A variety of reading disability associated with righc hemisphere lesions. Journal o f Neurology, Netnosurgery amd Psychiatry. 1962, 25, 339-344. ( b ) MORRISON,F. J., GIORDANI, B., & NAGY, J. Reading disability: an information processing analysis. Science, 1977, 196, 77-79. ROCK, I. Orientation and form. New York: Academic Press, 1973. RUDEL,R. G. The neurolog,ical assessment of learning disabilities. In S. G. Brainard ( E d . ) , Learning disa zlztres: zssues and recornmendations for research. Washington, D. C.: 1974. Pp. 123-141. (N.I.E. Conference Report, U. S. Department of HEW) SMITH,F., & HOLMES,L. D. The independence of letter, word and meaning identification in reading. Reading Research Quarterly, 1971, 6, 394-415. SMITH, M. J. Which hand is the eye of the blind? Genetic Prychology Monographs. 1929. 5. 209-252. STANDING,L., CONEZIO,J., & HABBR,R. Perception and memory for pictures: single trial learning of 2500 visual stimuli. Psychonomic Science, 1970, 15, 73-84. SYMMES,S. J., & RAPOPORT,L. J. Unexpected reading failure. (American Jownul o f Orthopsychirrtry, 1972, 42, 82-91. WITELSON,F. S. Abnormal righc hemisphere specialization in developmental dyslexia. In M. R. Knights & D. J. Bakker (Eds.). T h e newropsychology of learning diso+derr. Baltimore: Univer. Park Press, 1976. Pp. 233-255. YENI-KOMSHIAN,H. G.,ISENBBRG, D., & GOLDBERG, H. Cerebral dominance and reading disability: left visual field deficits in poor readers. Neuropsychologia, 1975, 13.83-93. Accepted August 17, 1978.
