Journal o f Autism and Developmental Disorders, Vol. 20, No. 1, 1990
Comprehension of Concrete and Abstract Words in Autistic Children Gall A. Eskes, 2 Susan E. Bryson, and Terry A. McCormick Dalhousie University
This study employed the Stroop paradigm to examine comprehension o f single words in autistic children. The words o f interest varied along a concreteabstract dimension. In the Stroop paradigm, subjects are asked to name the color o f ink in which color words are printed. Comprehension is indexed by the degree to which the automatic processing o f words interferes with the color-naming task. For both concrete and abstract words, autistic children showed the same degree o f interference as reading-matched controls. The findings corroborate and extend previous work suggesting that autistic children understand, and by implication, can mentally represent, at least some word meanings.
Disturbances in the development of language are one of the most striking features of early childhood autism. However, several lines of research suggest that the basic deficit is not linguistic as such, but rather a more general cognitive impairment in the processing of semantic information. Empirical evidence for this hypothesis was first provided by the early studies of Hermelin and O'Connor (1967, 1970). Autistic and carefully matched subnormal children were asked to recall a series of unrelated words, meaningful sentences, or randomly ordered lists of words derived from at least two semantic categories. Although memory per se was not impaired
~This research was supported by grants from the Hospital for Sick Children Foundation, Toronto, Ontario, NSERC of Canada and Dalhousie RDFS. We thank the children and parents who made this research possible, and the anonymous reviewers for their thoughtful comments. 2Address all correspondence to Gall A. Eskes, Department of Psychology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada. 61 0162-3257/90/0300-0061506.00/09 1990PlenumPublishingCorporation
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Eskes, Bryson, and McCormick
in the autistic children, their recall, unlike that of the controls, was not facilitated by the semantic relationships among words. Further evidence for an apparent insensitivity to meaning is that the autistic children did not organize their responses into semantically related categories. Later studies (Frith, 1969; Fyffe & Prior, 1978; Tager-Flusberg, 1986; Wolff& Barlow, 1979) have generally confirmed these initial results. In a subsequent series of experiments, Tager-Flusberg (1985a, 1985b, 1985c) explored the possibility that autistic children may differ in how the meanings of words and their underlying concepts are represented and organized in memory. The children categorized pictorically represented objects into basic and superordinate level concepts (e.g., bird and tool, respectively; cf. Rosch, 1975). Regardless of whether the concepts were represented by pictures or words, autistic children showed the same pattern of correct and incorrect responses as language-matched controls, suggesting that the nature and extension of concepts and word meanings (at least for concrete objects) is similar across groups. Autistic children's knowledge of word meanings was also investigated by Bryson (1983), using different versions of the Stroop (1935) color-word test. In the traditional Stroop task, subjects are asked to name the colors of ink in which color words are written. Incongruity between the two stimulus dimensions (e.g., the word blue written in red ink) produces interference, as indicated by increased latencies in naming the ink colors. Interference is assumed to result from automatic processing of the words (even though that is not the task), thereby competing with the ink-naming responses. In Bryson's study, subjects named the ink colors of incongruously colored forms (e.g., green lips) and color words, and they reported the number of circles adjacent to incongruous numbers (e.g., 2 circles presented with the number 3). In each task, the incongruity in stimulus information produced as much interference in high-functioning autistic children as in reading-matched controis. Since interference is considered a measure of automatic access to the meaning of the stimulus (Posner & Snyder, 1975), these data suggest that autistic children's comprehension of simple concepts such as color, number, and form parallels that of matched normal children. The results for color word incongruity have been confirmed by Frith and Snowling (1983), thus prividing converging evidence for Tager-Flusberg's (1985a, 1985b, 1985c) claim that the representation of meaning does not distinguish autistic from control children. One question that remains to be determined is whether autistic children also understand more abstract terms such as life or dream. Abstract ideas differ from the concrete by virtue of having less tangible referents. Available evidence suggests that autistic children have difficulty with complex abstractions, perhaps because the information to be extracted cannot be perceived directly (cf. Menyuk & Quill, 1985). Clinical observations and lan-
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Comprehension in Autistic Children
guage studies indicate, for example, that their speech is very literal and dominated by concrete terms (Kanner, 1943; Ricks & Wing, 1975). Frith and Snowling (1983) did report that high-functioning autistic children, like normal controls, find concrete words easier to read than abstract words matched for word frequency. The authors noted, however, that decoding speed does not constitute a direct test of whether the children actually access the meaning of the individual words. The present study was designed to extend previous investigations of single-word comprehension in autistic children. The Stroop task was used to examine the children's understanding of words that refer not only to concrete concepts (e.g., table) but also to more abstract, less imageable ideas (e.g., life). Previous work with the Stroop indicates that in normal children and adults, as words become more meaningful and more closely related to color, their ability to interfere with ink-color naming increases (Fox, Shor, & Steinman, 1971; Hochman, 1969; Klein, 1964). For example, while color words cause the most interference, common words cause more interference than rare words, and rare words in turn generate more interference than consonant nonsense words (Klein, 1964). A distinct advantage of the Stroop paradigm is that comprehension of individual words is accessed directly. Subjects are not required to generate a semantically ralated response or remember a series of related items, either of which could account for an apparent failure to appreciate the meaning of a stimulus. On the other hand, the Stroop does not access all aspects of word meaning, a matter to which we return later. In our study, concrete and abstract words were presented in a variation of the Stroop color-word test. Interference was taken as evidence that word meanings had been accessed. We also included pronounceable nonwords to ensure that any latency differences on the color-of-ink naming task did not reflect the time taken merely to decode (rather than comprehend) the relevant stimuli. The main question of interest was whether autistic children would show the same degree of interference as matched normal children when presented with abstract as well as concrete words. Our results provide preliminary evidence of autistic children's understanding of abstract ideas in the absence of confounding task demands.
METHOD
Subjects Eleven autistic and 11 normal children (10 male, 1 female in each group) participated is this experiment. Nine of the autistic children were identified through an epidemiological investigation of autistic conditions (Bryson, Clark, & Smith, 1988), the remaining three (including the one female) through
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Eskes, llryson, and McCormick Table I. Subject Data
Subject variables Age (years-months) Nonverbal intelligence* Receptive language Reading
Autistic
Control
M
M
SD
13-0 3.1 87.9 20.3 78.4 22.8 91.9 20.6
SD
8-2 0.5
*Nonverbal intelligence was measured using the Performance Scale of the Wechsler Intelligence Scale for Children-Revised, receptive language using the Peabody Picture Vocabulary Test-Revised, and reading ability (decoding) using the Wide Range Achievement Test-Revised. Data are expressed as standard scores.
a local society for autistic persons. Each child conformed to the new research diagnostic criteria for autism (summarized by Denckla, 1986, and operationalized by Bryson et al., 1988). They presented with (a) abnormal attachment behavior and/or a failure to develop reciprocal relationships, (b) deviant and noncommunicative language, and (c) repetitive behaviors involving both simple motor stereotypies and more complex, compulsive rituals (see Bryson et al., 1988, for a more detailed description of the children). The children also met the DSM-III-R criteria (American Psychiatric Association, 1987). All but one of the autistic children were enrolled in the regular school system; seven were in special classes, and four in regular classes, either fullor part-time. Relevant descriptive data on this relatively high-functioning, literate, population are provided in Table I. With one exception, all scored within the mildly retarded to normal range of intelligence (IQ > 70) on the Performance Scale of the Wechsler Intelligence Scale for Children-Revised (WlSC-R). Standard reading (decoding) scores on the Wide Range Achievement Test-Revised (WRAT-R) are comparable to measured nonverbal intelligence, while performance on a measure of receptive language (Peabody Picture Vocabulary Test, PPVT) is relatively depressed. The autistic children ranged in age from 8-19 years (M = 13 years). The normal children were matched to the autistic children on the baseline measure of speed of reading words in black print (described below). Pilot testing suggested that a group of normal children approximately 5 years younger was required for this purpose. The normal controls had a mean age of 8 years 2 months, and ranged in age from 7-9 years. None had a history of any learning difficulties. The two groups were matched on reading speed rather than on some measure of receptive language to avoid the circularity inherent in matching on the variable under study. We note, however, that on a measure of receptive language (the PPVT), the age-equivalent score of our autistic sample (9 years 7 months) is somewhat higher than the mean
Comprehension in Autistic Children
65
chronological age (8 years 2 months) o f the control children, w h o are assumed to be o f average (or high average) abilities.
Materials Eight cards (27.5 • 20.5 cm) were prepared as stimuli. A Color Card and a Black Word Card served as baseline measures. The six experimental cards included a Stroop Color-Word Card, a Color-Related Word Card, a Concrete Word Card, an Abstract Word Card, a Pronounceable Nonsense Word Card, and a Consonant Nonsense Word Card. With the exception of the Black Word Card, each card consisted of 20 items printed in one of four colors (red, blue, green, or brown), and arranged in a 4 x 5 matrix. The colors appeared equally often on each card, with no two instances of a color occurring in sequence horizontally. Items on the Color Card consisted of 20 groups of three asterisks, each triad appearing in one of the four colors. On the Black Word Card (the baseline measure for matching the two groups of subjects), 16 words were arraged randomly in a 4 • 4 matrix. This card consisted of the real words described below printed in black ink. Each of the experimental cards consisted of four different, randomly ordered, items, each repeated five times. On the Stroop Color-Word Card (STR), the words red, blue, green, and brown appeared in incongruent colors of ink (e.g., red in blue ink). The Color-Related Word Card (CR) consisted of words that are not themselves color names but are associated with the color red, blue, green, or brown (fire, sky, grass, and dirt, respectively). These words had mean levels of concreteness and imagery of 6.62 and 6.54 (out of a possible 7; Paivio, Yule, & Madigan, 1968), and were printed in inappropriate colors of ink (e.g., grass in red ink). The Concrete Word Card (CON) comprised words referring to common objects (table, book, ship, house; concreteness and imagery = 6.96 and 6.57, respectively). The Abstract Word Card (ABS) consisted of the words idea, life, dream, and time, all of which refer to concepts that connot be experienced directly by the senses (concreteness and imagery = 2.48 and 3.75). The items on the Pronounceable Nonsense Word Card (NWP) were orthographically and phonologically similar to real English words, but were not real words (ploun, vaf, gebe, biese). On the Consonant Nonsense Word Card (NWC), the items comprised only consonants, and thus did not either look or sound like real words (hjbm, dsqf, kpqx, vgrtc). All words were printed in lower case letters, and were monosyllabic (except for table). They were matched for length across cards, and, in the case of real words, for frequency of use (Thorndike & Lorge, 1944).
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Eskes, Bryson, and McCormick
Procedure All children were tested individually in a quiet room, either in their home or school. The child and two Experimenters were seated at a table side by side. Each of the eight stimulus cards was presented three times during one 30-min testing session. The children were given a rest period after each eightcard block, with each block consisting o f one presentation o f each of the eight different cards. Order of presentation within each block was randomized, except for the Black Word Card which always appeared first. At the beginning of each session, the children were given a practice card to ensure that they understood the experimental task. The practice card consisted o f four rows of four items. Words (color words and concrete words different from those used in the experiment) printed in one of the four colors alternated with asterisk triads, such that an equal number o f both words and asterisks appeared in each color. The Experimenter demonstrated the task by naming the colors o f ink of the items in the first two rows, and then asked the child to do the same on the next two rows. In the experiment proper, the Experimenter pointed to the upper lefthand corner, while asking the child to start at the top and read all the words on the Black Word Card as quickly as possible. For all other cards, the children were instructed in the same manner to name the ink colors o f all the words or asterisks. None of the children had any difficulty following the instructions. Response times for each card were recorded by one Experimenter, and accuracy of responses by the other Experimenter. Timing began when the Experimenter said "start," and ended when the child produced his last response. All sessions were audiotaped for later verification. The two dependent measures were interference scores and errors. Interference for each card was calculated for each child by subtracting the mean response time on the Color Card from the mean response time on each of the six experimental cards. Responses were scored as errors if the child either named the color incorrectly or read the word rather than naming the color.
RESULTS The two groups were matched for reading ability, as measured by their speed of reading the words on the Black Word Card. The mean reading speed for the autistic group and the normal controls was 11.5 sec (4.5-19.9 sec) and 12.1 sec (7.2-17.4 sec), respectively, t(20) = 0.40, p > .05.
Comprehension in Autistic Children
67
INTERFERENCESCORES 3 0 1-t
I ~
~
1
25. S
C 20' 0 R 15 E S
10 5 0 NWC
Ng/P
ABS
CON
CR
STR
CARDS
Fig. 1. Mean (and SD) interference scores of normal and autistic children on the different Stroop conditions. Abbreviations: NWC, consonant nonsenseword card; NWP, pronounceablenonsenseword card; ABS, abstract word card; CON, concreteword card; CR, colorrelated word card, STR, Stroop color-word card.
Interference Data Mean interference scores on each experimental card were computed for every child, and were averaged for each group (see Figure 1). Before subjecting these data to an analysis of variance, we first determined whether one group was more variable in their responses than the other. Variability Between Groups. The lack o f a difference in variability between the two groups was verified in two ways. First, variability across the three individual trials for each card was compared between groups by an analysis of variance on the standard deviations o f each mean for each subject. The A N O V A examined the significance of two factors, G r o u p (2 levels) and Cards (6 levels, repeated measures). There was no significant main effect of G r o u p (mean SD = 4.7 vs. 3.6, autistic vs. control), F(1, 10) -- 1.52, nor was the interaction between G r o u p and Card significant, F(7, 70) = 0.75. Second, homogeneity of variance of the m e a n interference scores for each card was analyzed between groups using the Levene Test for H o m o g e n e i t y o f Variances (Keppel, 1973). The results indicated that the variability of the two groups did not differ, F(1, 10) = 0.680, p > .05. Variability Within Groups. The pattern o f individual mean interference scores within the autistic group was examined qualitatively rather than quantitatively because o f the small n u m b e r o f subjects. A careful scrutiny of the data failed to yield any evidence that responses o f the autistic children were
68
Eskes, Bryson, and McCormick Table I1. Summary of Statistical Analyses for the Combined
Groups Source of interference
F p Pronounceability NWC vs. NWP 8.56 .01 Meaning NWP vs. CON 14.77 .003 NWP vs. ABS 12.24 .01 NWP vs. CR 6.85 .02 Color-related meaning CON vs. CR 4.53 ns Abstract meaning CON vs. ABS 5.40 .04 Stroop effect CON vs. STR 34.20 .001 aNWC = consonant nonsense word card, NWP = pronounceable nonsense word card, CON = abstract word card, CR = color-related word card, STR = Stroop color-word card. Cards*
related to nonverbal intelligence, receptive language, or reading ability (cf. Table I). Parametric Statistics. An analysis of variance o f the interference scores examined the significance of two factors, G r o u p (2 levels) and Cards (6 levels, repeated measures). There was no significant main effect of Group, F(1, 20) = 2.04, and no significant G r o u p • Card interaction, F(5, 100) = 0.02. The main effect of Cards was significant, F(5,100) = 39.62, p < .001. Since the results of the two groups did not differ, the data were combined for further analysis. Planned comparisons on the interference scores, collapsed over groups, were conducted between N W C and N W P (the effect o f pronounceability), N W P and each of C O N , ABS, and CR (the effect o f meaning), C O N and CR (the effect o f color-related meaning), C O N and ABS (the effect o f abstract meaning), and C O N and STR (the Stroop effect). Relevant comparisons are summarized in Table II. Interference in color naming on the N W C Card was significantly less than that generated by the N W P Card (4.8 vs. 7.2 sec). However, pronounceable nonwords produced shorter color-naming latencies than meaningful words; interference on the N W P Card was significantly less than that associated with the C O N , ABS, or CR Cards (7.2 vs. 11.0, 9.1, 9.3 sec, respectively). Finally, the ABS and CR Cards generated significantly less interference than the C O N condition (11.0 vs. 9.1, 9.3 sec), which in turn generated less interference than the STR Card (11.0 vs. 18.0 sec).
Errors The mean number of errors on each card was computed for every child, and was averaged for each group. A two-way analysis o f variance revealed a significant main effect of Cards, F(7, 140) = 18.65, p < .001. Once again,
Comprehension in Autistic Children
69
there was no significant main effect of Group, and no significant Group x Card interaction (Fs = 0.33 and 1.06, respectively). Newman-Keuls multiple comparisons of errors between cards, averaged for the two groups, showed that there were significantly more errors on the STR Card than on any other card (p < .01). No other comparisons were significant. DISCUSSION This study used a variation of the Stroop task to examine whether autistic children comprehend single words that differ along a concrete-abstract dimension. Our high-functioning autistic group showed the same amount of interference under all experimental conditions as younger normal children matched for reading (decoding) ability. Interference in color naming is assumed to reflect automatic processing of the meaning of a stimulus. Thus, at this level of processing, both concrete and abstract words appear as meaningful to autistic children as to matched normal controls. The finding that autistic children understand concrete words presented singly is supported by previous research using the Stroop as well as other paradigms (Bryson, 1983; Frith & Snowling, 1983; Tager-Flusberg, 1985a, 1985b, 1985c). The present study extends this work by showing that autistic children also possess at least some appreciation of more complex, abstract concepts such as life or time. Indeed, their response to words whose meanings are not directly available to the senses are comparable to those of readingmatched controls. We thus conclude that the comprehesion abilities of some autistic children (i.e., high-functioners) may be more extensive than previously thought (Menyuk & Quill, 1985; Ricks & Wing, 1975). Despite our failure to show any group differences, color-naming responses did differ across stimulus conditions. The pronounceable nonwords were more interfering than the unpronounceable nonwords, suggesting that both groups of children are sensitive to the orthographic regularity of pronounceable items. This finding is consistent with earlier developmental work (Guttentag, 1979; Guttentag & Haith, 1978) showing that pronounceability begins to interfere with picture naming by the third grade. Note also that all real word conditions resulted in significantly more interference than that produced by the pronounceable nonwords. This effect of meaning confirms results of previous authors, who have concluded that the degree of interference generated is a direct functon of how meaningful the words are to the reader (Fox et al., 1971; Hochman, 1969; Klein, 1964). As expected, the greatest amount of interference was seen in the standard Stroop condition (incongruent color words). This result is well
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Eskes, Bryson, and McCormick
documented in normal children and adults (Hochman, 1969; Klein, 1964). In contrast to previous findings, color-related words did not generate more interference than real words (matched for concreteness and imageability) that have no apparent relationship to color. An additional study with adults using the same materials also failed to generate the expected color-related effect. Our discrepant results may reflect the use of considerably fewer stimulus items than employed in earlier work (Klein, 1964). However, since this effect did not obtain for any group, it does not detract from our main conclusion that autistic children have at least some comprehension of a variety of words, including those that refer to concepts that are generally considered more complex and nonimageable. Note further that while each word class was more interfering than nonwords, concrete words generated more interference than the abstract words. As indicated above, degree of interference is considered an index of the relative meaningfulness of a stimulus. On this assumption, our findings suggest that abstract words are less meaningful for both autistic and normal children than frequency-matched concrete words. On the other hand, our concrete-abstract effect may reflect differential rates of accessing meaning rather than actual differences in the degree to which the stimuli are meaningful. Frith and Snowling (1983) reported a related effect in normal and autistic children. In their study, concrete words were easier to read than abstract words matched for frequency. Recent studies of semantic priming indicate that semantic relationships based on more abstract, conceptual attributes (e.g., categories) take longer to process than those based on perceptual features (e.g., color or shape; Flores d'Arcais, Schreuder, & Glazenborg, 1985). Such findings serve to underscore the underlying differences in how each word class is represented (Coltheart, 1980; Kroll & Merves, 1986; Paivio, 1971). We emphasize in this context that the Stroop phenomenon (i.e., interference in ink-color naming) is assumed to operate at an automatic level (Posnet & Snyder, 1975). Processes that function automatically may not access all aspects of meaning, or, in the case of the Stroop, all aspects of meaning, particularly the less tangible, may not be accessed within the time taken to decode the words. At the extreme, abstract words may produce more interference than pronounceable nonwords only beccause the former are more familiar. Thus, our failure to find any group differences in the processing of abstract words must be interpreted with caution. Our data do not address related questions such as whether the extensional, or perhaps even more likely, the intentional meanings of terms distinguish the autistic from other groups. Tager-Flusberg's (1985a, 1985b, 1985c) findings indicated that the way in which autistic children generalize (or extend) relatively concrete concepts is not unlike that o f developmentally matched controls. To our knowledge, no such data exist for concepts that are more abstract.
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Comprehension in Autistic Children
As noted earlier, Menyuk and Quill (1985) have proposed that autistic children tend to process the perceptual rather than the functional or more conceptual attributes of concepts. Representations based primarily on perceptual information may be sufficient for the tasks employed to date, and may therefore account for our and other's failures to demonstrate a comprehension deficit in autism. We are currently testing Menyuk and Quilrs hypothesis more directly by using a semantic priming paradigm. The critical question is whether autistic children respond differentially to semantically related and unrelated words when the relationship is defined by either perceptual and/or conceptual information. Menyuk and Quill, among others (Bartak, Rutter, Cox, 1975; Bartolucci, Pierce, & Streiner, 1980; Park, 1967; Frith & Snowling, 1983), also reported that autistic children have particular difficulty with terms that have no fixed referents, namely, relational terms such as prepositions or pronouns. An understanding of such terms depends on an appreciation of the entire context in which they appear. Researchers have only begun to explore the autistic child's comprehension of words presented in context (Frith & Snowling, 1983; Snowling & Frith, 1986). Studies such as the one reported here constitute a beginning in our attempt to bettter understand whether and how autistic children differ in the processing of incoming information. At present, converging evidence suggests that the representation of word meanings and their underlying conceptual structure does not deviate in autism. Such findings have led others to conclude that autistic children have the knowledge but are unable to use it in a meaningful way (Schwartz, 1981; Tager-Flusberg, 1986). Indeed, TagerFlusberg used this hypothesis to account for the fact that the same autistic children who produced prototypical responses to concepts and showed a sensitivity to their extensional meanings did not benefit from the semantic relatedness in Hermelin and O'Connor's (1967, 1970) memory task. That is, unlike controls, they did not recall words from the same semantic categories any better than random strings of words. We emphasize, however, that the "failure to use the knowledge" hypothesis does not constitute an explanation of why. It thus seems important to first preclude the possibiltiy that at least some knowledge in autistic children is represented in such a way that they do not have the cognitive flexibility to adapt to an ever-changing world or to communicate effectively with others.
REFERENCES
AmericanPsychiatricAssociation.(1987). Diagnostic and statistical manual of mental disorders (3rd ed., rev.). Washington, DC: Author. Bartak, L., Rutter, M., &Cox,A. (1975). A comparativestudyof infantileautismand specific developmentalreceptivelanguagedisorder: The children.British Journal of Psychiatry, 126, 127-145.
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Bartolucci, G., Pierce, S., & Streiner, D. (1980). Cross-sectional studies of grammatical morphemes in autistic and mentally retarded children. Journal of Autism andDevelopmental Disorders, 10, 39-50. Bryson, S. E. (1983). Interference effects in autistic children: Evidence for the comprehension of single stimuli. Journal of Abnormal Psychology, 92, 250-254. Bryson, S. E., Clark, B. S., & Smith, I. M. (1988). First report of a Canadian epidemiological study of autistic syndromes. Journal of Child Psychology and Psychiatry, 29, 433-445. Coltheart, M. (1980). Deep dyslexia: A right hemisphere hypothesis. In M. Coltheart, K. Patterson, & J. C. Marshall (Eds.), Deep dyslexia (pp. 326-380). London: Routledge & Kegan Paul. Denckla, M. B. (1986). Editorial: New diagnostic criteria for autism and related behavioral disorders-Guidelines for research protocols. Journal of American Academy of Child Psychiatry, 25, 221-224. Flores d'Arcals, G. B., Schreuder, R., and Glazenborg, G. (1985). Semantic activation during recognition of referential words. Psychological Research 47, 39-49. Fox, L., Shor, R., & Steinman, R. (1971). Semantic gradients and interference in naming color, spatial direction, and numerosity. Journal of Experimental Psychology, 91, 59-65. Frith, U. (1969). Emphasis and meaning in recall in normal and autistic children. Language and Speech, 12, 29-38. Frith, U., & Snowling, M. (1983). Reading for meaning and reading for sound in autistic and dyslexic children. British Journal of Developmental Psychology, 1, 329-342. Fyffe, C., & Prior, M. (1978. Evidence for language recoding in autistic, retarded and normal children: A re-examnation. British Journal of Psychology, 69, 393-402. Guttentag, R. (1979). Picture-naming interference with good and poor readers. Perceptual and Motor Skills, 49, 67-70. Guttentag, R., & Haith, M. (1978). Automatic processing as a function of age and reading ability. Child Development, 49, 707-716. Hermelin, B., & O'Connor, N. (1967). Remembering of words by psychotic and subnormal children. British Journal of Psychology, 58, 213-218. Hermelin, B., & O'Connor, N. (1970). Psychological experiments with autistic children. Oxford: Pergamon. Hochman, S. (1969). Stress and response competition in children's color-word performance. Perceptual and Motor Skills, 28, 115-118. Kanner, L. (1943). Autistic disturbances of affective contact. The Nervous Child, 2, 217-250. Keppel, G. (1973). Design and analysis: A researcher's handbook. Englewood ClifFs , NJ: Prentice-Hall. Klein, G. (1964). Semantic power measured through the interference of words with color-naming. American Journal of Psychology, 77, 576-588. Kroll, J., & Merves, J. (1986). Lexical access for concrete and abstract words. Journal of Experimental Psychology: Learning, Memory, and Cognition, 12, 92-107. Menyuk, P., and Quill, K. (1985). Semantic problems in autistic children. In E. Schopler & G. B. Mesibov (Eds.), Communication problems in autism. New York: Plenum Press. Paivio, A. V. (1971). Imagery and verbalprocesses. New York: Holt, Rinehart & Winston. Paivio A. V., Yuille, J. C., & Madigan, S. A. (1968). Concreteness, imagery, and meaningfulness values for 925 nouns. Journal of Experimental Psychology Monographs, 76(1, Pt. 2). Park, C. C. (1967). The seige. Toronto: Little, Brown. Posner, M., & Snyder, C. (1975). Attention and cognitive control. In R. Solso (Ed.), Information processing and cognition (pp. 55-85). Hillsdale, N J: Erlbaum. Ricks, D. M., & Wing, L. (1975). Language, communication, and the use of symbols in normal and autistic children. Journal of Autism and Childhood Schizophrenia, 5, 191-221. Rosch, E. (1975). Cognitive representations of semantic categories. Journal of Experimental Psychology: General, 104, 192-233. Schwartz, S. (1981). Language disabilities in infantile autism: A brief reveiw and comment. Applied Psycholinguistics, 2, 25-31. Snowling, M., & Frith, U. (1986). Comprehension in "hyperlexic" readers. Jouranl of Experimental Child Psychology, 42, 392-415.
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Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643-662. Tager-Flusberg, H. (1985a). Basic level and superordinate level categorization in autistic, mentally retarded, and normal children. Journal of Experimental Child Psychology, 40, 450-469. Tager-Flusberg, H. (1985b). The conceptual basic for referential word meaning in children with autism. Child Development, 56, 1167-1178. Tager-Flusberg, H. (1985c). Constraints on the representation of word meaning: Evidence from autistic and mentally retarded children. In M. Barrett & S. A. Kuczaj (Eds.), The development of word meaning. New York: Springer-Verlag. Tager-Flusberg, H. (1986). The semantic deficit hypothesis of autistic children's language. Australian Journal of Human Communication Disorders, 14, 51-58. Thorndike, E. L., & Lorge, I. (1944). The teacher's word book of 30,O00 words. New York: Teacher's College Bureau of Publications, Columbia University. Wolff, S., & Barlow, A. (1979). Schizoid personality in childhood: A comparative study of schizoid, autistic and normal children. Journal of Child Psychology and Psychiatry, 20, 29-46.
Comprehension of Concrete and Abstract Words in Autistic Children Gall A. Eskes, 2 Susan E. Bryson, and Terry A. McCormick Dalhousie University
This study employed the Stroop paradigm to examine comprehension o f single words in autistic children. The words o f interest varied along a concreteabstract dimension. In the Stroop paradigm, subjects are asked to name the color o f ink in which color words are printed. Comprehension is indexed by the degree to which the automatic processing o f words interferes with the color-naming task. For both concrete and abstract words, autistic children showed the same degree o f interference as reading-matched controls. The findings corroborate and extend previous work suggesting that autistic children understand, and by implication, can mentally represent, at least some word meanings.
Disturbances in the development of language are one of the most striking features of early childhood autism. However, several lines of research suggest that the basic deficit is not linguistic as such, but rather a more general cognitive impairment in the processing of semantic information. Empirical evidence for this hypothesis was first provided by the early studies of Hermelin and O'Connor (1967, 1970). Autistic and carefully matched subnormal children were asked to recall a series of unrelated words, meaningful sentences, or randomly ordered lists of words derived from at least two semantic categories. Although memory per se was not impaired
~This research was supported by grants from the Hospital for Sick Children Foundation, Toronto, Ontario, NSERC of Canada and Dalhousie RDFS. We thank the children and parents who made this research possible, and the anonymous reviewers for their thoughtful comments. 2Address all correspondence to Gall A. Eskes, Department of Psychology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada. 61 0162-3257/90/0300-0061506.00/09 1990PlenumPublishingCorporation
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Eskes, Bryson, and McCormick
in the autistic children, their recall, unlike that of the controls, was not facilitated by the semantic relationships among words. Further evidence for an apparent insensitivity to meaning is that the autistic children did not organize their responses into semantically related categories. Later studies (Frith, 1969; Fyffe & Prior, 1978; Tager-Flusberg, 1986; Wolff& Barlow, 1979) have generally confirmed these initial results. In a subsequent series of experiments, Tager-Flusberg (1985a, 1985b, 1985c) explored the possibility that autistic children may differ in how the meanings of words and their underlying concepts are represented and organized in memory. The children categorized pictorically represented objects into basic and superordinate level concepts (e.g., bird and tool, respectively; cf. Rosch, 1975). Regardless of whether the concepts were represented by pictures or words, autistic children showed the same pattern of correct and incorrect responses as language-matched controls, suggesting that the nature and extension of concepts and word meanings (at least for concrete objects) is similar across groups. Autistic children's knowledge of word meanings was also investigated by Bryson (1983), using different versions of the Stroop (1935) color-word test. In the traditional Stroop task, subjects are asked to name the colors of ink in which color words are written. Incongruity between the two stimulus dimensions (e.g., the word blue written in red ink) produces interference, as indicated by increased latencies in naming the ink colors. Interference is assumed to result from automatic processing of the words (even though that is not the task), thereby competing with the ink-naming responses. In Bryson's study, subjects named the ink colors of incongruously colored forms (e.g., green lips) and color words, and they reported the number of circles adjacent to incongruous numbers (e.g., 2 circles presented with the number 3). In each task, the incongruity in stimulus information produced as much interference in high-functioning autistic children as in reading-matched controis. Since interference is considered a measure of automatic access to the meaning of the stimulus (Posner & Snyder, 1975), these data suggest that autistic children's comprehension of simple concepts such as color, number, and form parallels that of matched normal children. The results for color word incongruity have been confirmed by Frith and Snowling (1983), thus prividing converging evidence for Tager-Flusberg's (1985a, 1985b, 1985c) claim that the representation of meaning does not distinguish autistic from control children. One question that remains to be determined is whether autistic children also understand more abstract terms such as life or dream. Abstract ideas differ from the concrete by virtue of having less tangible referents. Available evidence suggests that autistic children have difficulty with complex abstractions, perhaps because the information to be extracted cannot be perceived directly (cf. Menyuk & Quill, 1985). Clinical observations and lan-
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Comprehension in Autistic Children
guage studies indicate, for example, that their speech is very literal and dominated by concrete terms (Kanner, 1943; Ricks & Wing, 1975). Frith and Snowling (1983) did report that high-functioning autistic children, like normal controls, find concrete words easier to read than abstract words matched for word frequency. The authors noted, however, that decoding speed does not constitute a direct test of whether the children actually access the meaning of the individual words. The present study was designed to extend previous investigations of single-word comprehension in autistic children. The Stroop task was used to examine the children's understanding of words that refer not only to concrete concepts (e.g., table) but also to more abstract, less imageable ideas (e.g., life). Previous work with the Stroop indicates that in normal children and adults, as words become more meaningful and more closely related to color, their ability to interfere with ink-color naming increases (Fox, Shor, & Steinman, 1971; Hochman, 1969; Klein, 1964). For example, while color words cause the most interference, common words cause more interference than rare words, and rare words in turn generate more interference than consonant nonsense words (Klein, 1964). A distinct advantage of the Stroop paradigm is that comprehension of individual words is accessed directly. Subjects are not required to generate a semantically ralated response or remember a series of related items, either of which could account for an apparent failure to appreciate the meaning of a stimulus. On the other hand, the Stroop does not access all aspects of word meaning, a matter to which we return later. In our study, concrete and abstract words were presented in a variation of the Stroop color-word test. Interference was taken as evidence that word meanings had been accessed. We also included pronounceable nonwords to ensure that any latency differences on the color-of-ink naming task did not reflect the time taken merely to decode (rather than comprehend) the relevant stimuli. The main question of interest was whether autistic children would show the same degree of interference as matched normal children when presented with abstract as well as concrete words. Our results provide preliminary evidence of autistic children's understanding of abstract ideas in the absence of confounding task demands.
METHOD
Subjects Eleven autistic and 11 normal children (10 male, 1 female in each group) participated is this experiment. Nine of the autistic children were identified through an epidemiological investigation of autistic conditions (Bryson, Clark, & Smith, 1988), the remaining three (including the one female) through
64
Eskes, llryson, and McCormick Table I. Subject Data
Subject variables Age (years-months) Nonverbal intelligence* Receptive language Reading
Autistic
Control
M
M
SD
13-0 3.1 87.9 20.3 78.4 22.8 91.9 20.6
SD
8-2 0.5
*Nonverbal intelligence was measured using the Performance Scale of the Wechsler Intelligence Scale for Children-Revised, receptive language using the Peabody Picture Vocabulary Test-Revised, and reading ability (decoding) using the Wide Range Achievement Test-Revised. Data are expressed as standard scores.
a local society for autistic persons. Each child conformed to the new research diagnostic criteria for autism (summarized by Denckla, 1986, and operationalized by Bryson et al., 1988). They presented with (a) abnormal attachment behavior and/or a failure to develop reciprocal relationships, (b) deviant and noncommunicative language, and (c) repetitive behaviors involving both simple motor stereotypies and more complex, compulsive rituals (see Bryson et al., 1988, for a more detailed description of the children). The children also met the DSM-III-R criteria (American Psychiatric Association, 1987). All but one of the autistic children were enrolled in the regular school system; seven were in special classes, and four in regular classes, either fullor part-time. Relevant descriptive data on this relatively high-functioning, literate, population are provided in Table I. With one exception, all scored within the mildly retarded to normal range of intelligence (IQ > 70) on the Performance Scale of the Wechsler Intelligence Scale for Children-Revised (WlSC-R). Standard reading (decoding) scores on the Wide Range Achievement Test-Revised (WRAT-R) are comparable to measured nonverbal intelligence, while performance on a measure of receptive language (Peabody Picture Vocabulary Test, PPVT) is relatively depressed. The autistic children ranged in age from 8-19 years (M = 13 years). The normal children were matched to the autistic children on the baseline measure of speed of reading words in black print (described below). Pilot testing suggested that a group of normal children approximately 5 years younger was required for this purpose. The normal controls had a mean age of 8 years 2 months, and ranged in age from 7-9 years. None had a history of any learning difficulties. The two groups were matched on reading speed rather than on some measure of receptive language to avoid the circularity inherent in matching on the variable under study. We note, however, that on a measure of receptive language (the PPVT), the age-equivalent score of our autistic sample (9 years 7 months) is somewhat higher than the mean
Comprehension in Autistic Children
65
chronological age (8 years 2 months) o f the control children, w h o are assumed to be o f average (or high average) abilities.
Materials Eight cards (27.5 • 20.5 cm) were prepared as stimuli. A Color Card and a Black Word Card served as baseline measures. The six experimental cards included a Stroop Color-Word Card, a Color-Related Word Card, a Concrete Word Card, an Abstract Word Card, a Pronounceable Nonsense Word Card, and a Consonant Nonsense Word Card. With the exception of the Black Word Card, each card consisted of 20 items printed in one of four colors (red, blue, green, or brown), and arranged in a 4 x 5 matrix. The colors appeared equally often on each card, with no two instances of a color occurring in sequence horizontally. Items on the Color Card consisted of 20 groups of three asterisks, each triad appearing in one of the four colors. On the Black Word Card (the baseline measure for matching the two groups of subjects), 16 words were arraged randomly in a 4 • 4 matrix. This card consisted of the real words described below printed in black ink. Each of the experimental cards consisted of four different, randomly ordered, items, each repeated five times. On the Stroop Color-Word Card (STR), the words red, blue, green, and brown appeared in incongruent colors of ink (e.g., red in blue ink). The Color-Related Word Card (CR) consisted of words that are not themselves color names but are associated with the color red, blue, green, or brown (fire, sky, grass, and dirt, respectively). These words had mean levels of concreteness and imagery of 6.62 and 6.54 (out of a possible 7; Paivio, Yule, & Madigan, 1968), and were printed in inappropriate colors of ink (e.g., grass in red ink). The Concrete Word Card (CON) comprised words referring to common objects (table, book, ship, house; concreteness and imagery = 6.96 and 6.57, respectively). The Abstract Word Card (ABS) consisted of the words idea, life, dream, and time, all of which refer to concepts that connot be experienced directly by the senses (concreteness and imagery = 2.48 and 3.75). The items on the Pronounceable Nonsense Word Card (NWP) were orthographically and phonologically similar to real English words, but were not real words (ploun, vaf, gebe, biese). On the Consonant Nonsense Word Card (NWC), the items comprised only consonants, and thus did not either look or sound like real words (hjbm, dsqf, kpqx, vgrtc). All words were printed in lower case letters, and were monosyllabic (except for table). They were matched for length across cards, and, in the case of real words, for frequency of use (Thorndike & Lorge, 1944).
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Eskes, Bryson, and McCormick
Procedure All children were tested individually in a quiet room, either in their home or school. The child and two Experimenters were seated at a table side by side. Each of the eight stimulus cards was presented three times during one 30-min testing session. The children were given a rest period after each eightcard block, with each block consisting o f one presentation o f each of the eight different cards. Order of presentation within each block was randomized, except for the Black Word Card which always appeared first. At the beginning of each session, the children were given a practice card to ensure that they understood the experimental task. The practice card consisted o f four rows of four items. Words (color words and concrete words different from those used in the experiment) printed in one of the four colors alternated with asterisk triads, such that an equal number o f both words and asterisks appeared in each color. The Experimenter demonstrated the task by naming the colors o f ink of the items in the first two rows, and then asked the child to do the same on the next two rows. In the experiment proper, the Experimenter pointed to the upper lefthand corner, while asking the child to start at the top and read all the words on the Black Word Card as quickly as possible. For all other cards, the children were instructed in the same manner to name the ink colors o f all the words or asterisks. None of the children had any difficulty following the instructions. Response times for each card were recorded by one Experimenter, and accuracy of responses by the other Experimenter. Timing began when the Experimenter said "start," and ended when the child produced his last response. All sessions were audiotaped for later verification. The two dependent measures were interference scores and errors. Interference for each card was calculated for each child by subtracting the mean response time on the Color Card from the mean response time on each of the six experimental cards. Responses were scored as errors if the child either named the color incorrectly or read the word rather than naming the color.
RESULTS The two groups were matched for reading ability, as measured by their speed of reading the words on the Black Word Card. The mean reading speed for the autistic group and the normal controls was 11.5 sec (4.5-19.9 sec) and 12.1 sec (7.2-17.4 sec), respectively, t(20) = 0.40, p > .05.
Comprehension in Autistic Children
67
INTERFERENCESCORES 3 0 1-t
I ~
~
1
25. S
C 20' 0 R 15 E S
10 5 0 NWC
Ng/P
ABS
CON
CR
STR
CARDS
Fig. 1. Mean (and SD) interference scores of normal and autistic children on the different Stroop conditions. Abbreviations: NWC, consonant nonsenseword card; NWP, pronounceablenonsenseword card; ABS, abstract word card; CON, concreteword card; CR, colorrelated word card, STR, Stroop color-word card.
Interference Data Mean interference scores on each experimental card were computed for every child, and were averaged for each group (see Figure 1). Before subjecting these data to an analysis of variance, we first determined whether one group was more variable in their responses than the other. Variability Between Groups. The lack o f a difference in variability between the two groups was verified in two ways. First, variability across the three individual trials for each card was compared between groups by an analysis of variance on the standard deviations o f each mean for each subject. The A N O V A examined the significance of two factors, G r o u p (2 levels) and Cards (6 levels, repeated measures). There was no significant main effect of G r o u p (mean SD = 4.7 vs. 3.6, autistic vs. control), F(1, 10) -- 1.52, nor was the interaction between G r o u p and Card significant, F(7, 70) = 0.75. Second, homogeneity of variance of the m e a n interference scores for each card was analyzed between groups using the Levene Test for H o m o g e n e i t y o f Variances (Keppel, 1973). The results indicated that the variability of the two groups did not differ, F(1, 10) = 0.680, p > .05. Variability Within Groups. The pattern o f individual mean interference scores within the autistic group was examined qualitatively rather than quantitatively because o f the small n u m b e r o f subjects. A careful scrutiny of the data failed to yield any evidence that responses o f the autistic children were
68
Eskes, Bryson, and McCormick Table I1. Summary of Statistical Analyses for the Combined
Groups Source of interference
F p Pronounceability NWC vs. NWP 8.56 .01 Meaning NWP vs. CON 14.77 .003 NWP vs. ABS 12.24 .01 NWP vs. CR 6.85 .02 Color-related meaning CON vs. CR 4.53 ns Abstract meaning CON vs. ABS 5.40 .04 Stroop effect CON vs. STR 34.20 .001 aNWC = consonant nonsense word card, NWP = pronounceable nonsense word card, CON = abstract word card, CR = color-related word card, STR = Stroop color-word card. Cards*
related to nonverbal intelligence, receptive language, or reading ability (cf. Table I). Parametric Statistics. An analysis of variance o f the interference scores examined the significance of two factors, G r o u p (2 levels) and Cards (6 levels, repeated measures). There was no significant main effect of Group, F(1, 20) = 2.04, and no significant G r o u p • Card interaction, F(5, 100) = 0.02. The main effect of Cards was significant, F(5,100) = 39.62, p < .001. Since the results of the two groups did not differ, the data were combined for further analysis. Planned comparisons on the interference scores, collapsed over groups, were conducted between N W C and N W P (the effect o f pronounceability), N W P and each of C O N , ABS, and CR (the effect o f meaning), C O N and CR (the effect o f color-related meaning), C O N and ABS (the effect o f abstract meaning), and C O N and STR (the Stroop effect). Relevant comparisons are summarized in Table II. Interference in color naming on the N W C Card was significantly less than that generated by the N W P Card (4.8 vs. 7.2 sec). However, pronounceable nonwords produced shorter color-naming latencies than meaningful words; interference on the N W P Card was significantly less than that associated with the C O N , ABS, or CR Cards (7.2 vs. 11.0, 9.1, 9.3 sec, respectively). Finally, the ABS and CR Cards generated significantly less interference than the C O N condition (11.0 vs. 9.1, 9.3 sec), which in turn generated less interference than the STR Card (11.0 vs. 18.0 sec).
Errors The mean number of errors on each card was computed for every child, and was averaged for each group. A two-way analysis o f variance revealed a significant main effect of Cards, F(7, 140) = 18.65, p < .001. Once again,
Comprehension in Autistic Children
69
there was no significant main effect of Group, and no significant Group x Card interaction (Fs = 0.33 and 1.06, respectively). Newman-Keuls multiple comparisons of errors between cards, averaged for the two groups, showed that there were significantly more errors on the STR Card than on any other card (p < .01). No other comparisons were significant. DISCUSSION This study used a variation of the Stroop task to examine whether autistic children comprehend single words that differ along a concrete-abstract dimension. Our high-functioning autistic group showed the same amount of interference under all experimental conditions as younger normal children matched for reading (decoding) ability. Interference in color naming is assumed to reflect automatic processing of the meaning of a stimulus. Thus, at this level of processing, both concrete and abstract words appear as meaningful to autistic children as to matched normal controls. The finding that autistic children understand concrete words presented singly is supported by previous research using the Stroop as well as other paradigms (Bryson, 1983; Frith & Snowling, 1983; Tager-Flusberg, 1985a, 1985b, 1985c). The present study extends this work by showing that autistic children also possess at least some appreciation of more complex, abstract concepts such as life or time. Indeed, their response to words whose meanings are not directly available to the senses are comparable to those of readingmatched controls. We thus conclude that the comprehesion abilities of some autistic children (i.e., high-functioners) may be more extensive than previously thought (Menyuk & Quill, 1985; Ricks & Wing, 1975). Despite our failure to show any group differences, color-naming responses did differ across stimulus conditions. The pronounceable nonwords were more interfering than the unpronounceable nonwords, suggesting that both groups of children are sensitive to the orthographic regularity of pronounceable items. This finding is consistent with earlier developmental work (Guttentag, 1979; Guttentag & Haith, 1978) showing that pronounceability begins to interfere with picture naming by the third grade. Note also that all real word conditions resulted in significantly more interference than that produced by the pronounceable nonwords. This effect of meaning confirms results of previous authors, who have concluded that the degree of interference generated is a direct functon of how meaningful the words are to the reader (Fox et al., 1971; Hochman, 1969; Klein, 1964). As expected, the greatest amount of interference was seen in the standard Stroop condition (incongruent color words). This result is well
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Eskes, Bryson, and McCormick
documented in normal children and adults (Hochman, 1969; Klein, 1964). In contrast to previous findings, color-related words did not generate more interference than real words (matched for concreteness and imageability) that have no apparent relationship to color. An additional study with adults using the same materials also failed to generate the expected color-related effect. Our discrepant results may reflect the use of considerably fewer stimulus items than employed in earlier work (Klein, 1964). However, since this effect did not obtain for any group, it does not detract from our main conclusion that autistic children have at least some comprehension of a variety of words, including those that refer to concepts that are generally considered more complex and nonimageable. Note further that while each word class was more interfering than nonwords, concrete words generated more interference than the abstract words. As indicated above, degree of interference is considered an index of the relative meaningfulness of a stimulus. On this assumption, our findings suggest that abstract words are less meaningful for both autistic and normal children than frequency-matched concrete words. On the other hand, our concrete-abstract effect may reflect differential rates of accessing meaning rather than actual differences in the degree to which the stimuli are meaningful. Frith and Snowling (1983) reported a related effect in normal and autistic children. In their study, concrete words were easier to read than abstract words matched for frequency. Recent studies of semantic priming indicate that semantic relationships based on more abstract, conceptual attributes (e.g., categories) take longer to process than those based on perceptual features (e.g., color or shape; Flores d'Arcais, Schreuder, & Glazenborg, 1985). Such findings serve to underscore the underlying differences in how each word class is represented (Coltheart, 1980; Kroll & Merves, 1986; Paivio, 1971). We emphasize in this context that the Stroop phenomenon (i.e., interference in ink-color naming) is assumed to operate at an automatic level (Posnet & Snyder, 1975). Processes that function automatically may not access all aspects of meaning, or, in the case of the Stroop, all aspects of meaning, particularly the less tangible, may not be accessed within the time taken to decode the words. At the extreme, abstract words may produce more interference than pronounceable nonwords only beccause the former are more familiar. Thus, our failure to find any group differences in the processing of abstract words must be interpreted with caution. Our data do not address related questions such as whether the extensional, or perhaps even more likely, the intentional meanings of terms distinguish the autistic from other groups. Tager-Flusberg's (1985a, 1985b, 1985c) findings indicated that the way in which autistic children generalize (or extend) relatively concrete concepts is not unlike that o f developmentally matched controls. To our knowledge, no such data exist for concepts that are more abstract.
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Comprehension in Autistic Children
As noted earlier, Menyuk and Quill (1985) have proposed that autistic children tend to process the perceptual rather than the functional or more conceptual attributes of concepts. Representations based primarily on perceptual information may be sufficient for the tasks employed to date, and may therefore account for our and other's failures to demonstrate a comprehension deficit in autism. We are currently testing Menyuk and Quilrs hypothesis more directly by using a semantic priming paradigm. The critical question is whether autistic children respond differentially to semantically related and unrelated words when the relationship is defined by either perceptual and/or conceptual information. Menyuk and Quill, among others (Bartak, Rutter, Cox, 1975; Bartolucci, Pierce, & Streiner, 1980; Park, 1967; Frith & Snowling, 1983), also reported that autistic children have particular difficulty with terms that have no fixed referents, namely, relational terms such as prepositions or pronouns. An understanding of such terms depends on an appreciation of the entire context in which they appear. Researchers have only begun to explore the autistic child's comprehension of words presented in context (Frith & Snowling, 1983; Snowling & Frith, 1986). Studies such as the one reported here constitute a beginning in our attempt to bettter understand whether and how autistic children differ in the processing of incoming information. At present, converging evidence suggests that the representation of word meanings and their underlying conceptual structure does not deviate in autism. Such findings have led others to conclude that autistic children have the knowledge but are unable to use it in a meaningful way (Schwartz, 1981; Tager-Flusberg, 1986). Indeed, TagerFlusberg used this hypothesis to account for the fact that the same autistic children who produced prototypical responses to concepts and showed a sensitivity to their extensional meanings did not benefit from the semantic relatedness in Hermelin and O'Connor's (1967, 1970) memory task. That is, unlike controls, they did not recall words from the same semantic categories any better than random strings of words. We emphasize, however, that the "failure to use the knowledge" hypothesis does not constitute an explanation of why. It thus seems important to first preclude the possibiltiy that at least some knowledge in autistic children is represented in such a way that they do not have the cognitive flexibility to adapt to an ever-changing world or to communicate effectively with others.
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Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18, 643-662. Tager-Flusberg, H. (1985a). Basic level and superordinate level categorization in autistic, mentally retarded, and normal children. Journal of Experimental Child Psychology, 40, 450-469. Tager-Flusberg, H. (1985b). The conceptual basic for referential word meaning in children with autism. Child Development, 56, 1167-1178. Tager-Flusberg, H. (1985c). Constraints on the representation of word meaning: Evidence from autistic and mentally retarded children. In M. Barrett & S. A. Kuczaj (Eds.), The development of word meaning. New York: Springer-Verlag. Tager-Flusberg, H. (1986). The semantic deficit hypothesis of autistic children's language. Australian Journal of Human Communication Disorders, 14, 51-58. Thorndike, E. L., & Lorge, I. (1944). The teacher's word book of 30,O00 words. New York: Teacher's College Bureau of Publications, Columbia University. Wolff, S., & Barlow, A. (1979). Schizoid personality in childhood: A comparative study of schizoid, autistic and normal children. Journal of Child Psychology and Psychiatry, 20, 29-46.
