Deaf Children's Understanding of Beliefs and Desires

Transcription

1 Deaf Children's Understanding of Beliefs and Desires Lucy Steeds University of Oxford Karen Rowe University of Bristol Ann Dowker University of Oxford Twenty-two children (5-12 years old) who were profoundly, prelingually deaf were given two tests designed to tap their "theory of mind," that is, their ability to attribute independent mental states to other people. The tests were versions of Baron-Cohen, Leslie, and Frith's Sally-Anne task and of Baron-Cohen's breakfast task. Seventy percent of the children were successful on all questions requiring belief attribution, a considerably and significantly larger percentage than the 29% obtained by Peterson and Siegal for a similar sample, though it is still lower than would be expected on the basis on chronological age. Children were universally successful on questions requiring the attribution of desire. We discuss implications of the findings. A child credited with having a "theory of mind" is able to attribute independent mental states to himself or herself and others in order to predict and explain behavior (Premack & Woodruff, 1978). Despite the somewhat misleading term, this child need only take account of another person's beliefs, desires, and thoughts; it is not assumed that he or she conceives of these mental states as unobservable entities. In other words, a child with a theory of mind need not have postulated any theoretical constructs (quasi-scientifically). For convenience, the term theory of mind will be used in this article as it has frequently been used in the litera- We think the staff and pupils at Elmfidd School in Bristol and the Frank Barnes School in London; Dr. J. G. Kyle «t the Centre for Deaf Studies, University of Bristol; Dr. R. W. Hiorns for his advice on statistics; and Prof. R. Campbell and Dr. P. L. Harris for helpful discussion. Prof. C Peterson and two anonymous reviewers provided useful feedback on earlier drafts. Correspondence should be sent to Ann Dowker, Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford OX1 3UD, England. Copyright 1997 Oxford Univertity Press. CCC ture: to refer to children's ability to explicitly take account of other people's mental states in a test situation. No assumptions are made either about the presence or absence of theoretical constructs, or about the extent to which children's performance on such tasks may result in underestimates (Chandler, Fritz, & Hala, 1989; Clements & Perner, 1994) or overestimates (Clark, 1990; Murray & Field, 1990; Happe, 1995) of their implicit understanding of mental states in a more naturalistic context. Experiments testing for theory of mind have aimed to tap children's understanding of several different mental states and have taken a variety of forms. The first such experiment (Wimmer & Perner, 1983) and many subsequently (e.g., Baron-Cohen, Leslie, & Frith, 1985; Perner, Ruffman, & Leekam, 1994) have focused on whether young children can predict another person's behavior as based on his or her mistaken belief. There is some agreement that success in these so-called false-belief tasks typically emerges in normal children when they are around 4 years old. Growing evidence now shows that many autistic children have difficulties with tasks that assess theory of mind (e.g., Baron-Cohen et al., 1985), and attempts have been made to account for the full range of autistic deficits in terms of a theory-of-mind impairment (e.g., Leslie, 1987, 1994; Baron-Cohen, 1993). This has led to proposals of a theory-of-mind module that is impaired or absent in autism. A difficulty for such theories is that diagnostic criteria for autism include the development of symptoms before the age of 3 (DSM-IV):

2 186 Journal of Deaf Studies and Deaf Education 2:3 Summer 1997 that is, autistic children are already showing the disorder at an age when normal children also do not pass false-belief tasks. Attempts to reconcile the conflicting evidence range from suggestions that theory of mind depends on a specific brain mechanism that is present from birth but must mature before theory of mind can be manifested (cf. Fletcher, Happe, Frith, Baker, Dolan, Frackowiack, & Frith, 1995) to proposals that false-belief understanding develops out of other capacities that develop earlier, for example, pretend play (Leslie, 1987) and shared attention (Baron-Cohen, 1991b, 1993, 1994; Baron-Cohen, Cox, Baird, Sweetenham, Nightingale, Morgan, Drew, & Charman, 1996). An alternative or complementary theory is that the rate and extent of development of theory of mind may be influenced by exposure to conversations about mental states (cf. Perner, Ruffman, & Leekam, 1994; Jenkins & Astington, 1996) and that the severe communication disorder of autistic children prevents them from making adequate use of such conversations. Some support for the latter theory comes from findings of associations between verbal ability and theory of mind acquisition in both normal children (Happe, 1995; Jenkins & Astington, 1996) and autistic children (Happe, 1995; Sparrevohn & Howie, 1995), though a much higher verbal mental age was necessary for theory of mind tasks to be passed by autistic than normal children. Also, causal primacy has not been established. If exposure to communication is important to the development of a theory of mind, then one would expect that nonautistic children with communication disorders would also be delayed in theory-of-mind acquisition. There have been several attempts to study this topic Specifically language-impaired (SLI) children are sometimes used as controls for autistic children (e.g., Leslie & Frith, 1988; Perner, Frith, Leslie, & Leekam, 1989) and generally do much better than autistic children in theory-of-mind tasks. It should be noted, however, that SLI is a very heterogeneous condition, and that Shields, Varley, Broks, and Simpson (1996) have found impaired performance on theory-of-mind tasks by children with semantic pragmatic deficits (those that would have the greatest eflfect on comprehension), but not in children with phonological and syntactic deficits. The technique pioneered by Hermelin and O'Connor (1978) of comparing autistic groups with children with specific sensory impairments has also been used. For example, McAlpine and Moore (1995) studied theory of mind in blind children. Although blind children are not impaired in verbal communication, they are impaired in some forms of nonverbal communication, and in particular are not able to detect eye direction: a skill that Baron-Cohen and others (Baron-Cohen, 1993, 1994; Baron-Cohen, Campbell, Karmiloflf- Smith, Grant, & Walker, 1995; Campbell, 1994) regarded as important, though not absolutely essential, for the development of shared attention. McAlpine and Moore (1995) did indeed find that blind children were somewhat delayed in passing a false-belief task, though this may have been in part due to the greater information-processing demands of such a task for children who cannot use visual cues. The focus of this study is performance on theoryof-mind tasks by prelingually deaf children. Being born unable to hear does not automatically give rise to communication difficulties: studies of deaf children born to signing deaf parents have found a timetable of language acquisition roughly parallel to that of hearing children, including an early stage of manual babbling (e.g., Pettito & Marentette, 1991). Nevertheless, only a minority of deaf children have parents who are fluent signers and thus a deaf child's linguistic development is usually delayed, at least until he or she joins a community of native signers in primary school (and probably sometime beyond this, given the Total Communication, TC, ethos of most British schools for the deaf). Several studies have found that relatively few hearing parents achieve sufficient proficiency in manual communication to converse freely with their deaf children about imaginary or unobservable topics (e.g., M. Harris, 1992; Marschark, 1993), and further evidence shows that many deaf children start talking about others' mental states only when they start at a school for the deaf (Wood, Wood, Griffith, & Howarth, 1986). As a result of limited early exposure to language, it seems many deaf children will be delayed in gaining conversational access to information about the intangible thoughts and feelings of others. Furthermore, it is plausible that this will delay theory-of-mind development. Consistent with this theory, Peterson and Siegal (1995) reported that children aged 8 13 who were pro-

3 Understanding of Beliefs and Desires 187 foundly, prelingually deaf struggled with a false-belief test: only 35% passed a version of the classic "Sally- Anne" task (Baron-Cohen et al., 1985), which tests the understanding that someone who has not seen an object being moved will believe it to be in its original rather than actual location, and normally presents little problem for hearing children past their fourth birthday. The level of performance shown by deaf children did not differ significantly from that reported for autistic children of a comparable (nonverbal) mental age (Baron-Cohen et al., 1985). These results were replicated in a later comparison of deaf and autistic children across a wider age range (Peterson & Siegal, 1996). This study was essentially a reexamination of the claims made by Peterson and Siegal (1995), using an English sample and a wider range of tests. A highly similar, if slightly younger, sample of children participated in two different false-belief tests: the modified Sally-Anne task used by Peterson and Siegal and Baron-Cohen's (1991a) adaptation of a task devised by Harris, Johnson, Hutton, Andrews, and Cooke (1989). Inclusion of this second task, which demands emotion prediction rather than behavior prediction, gave a broader base on which to establish the children's understanding of false-belief, as recommended by Gray and Hosie (1996). It also offered a comparison of children's understanding of desires with their understanding of beliefs. There were two grounds for predicting that understanding of desires might be easier for the deaf children than understanding of beliefs. The first was that some previous studies suggest that both normal children (Wellman & Bartsch, 1988; Wellman & Woolley, 1990) and autistic children (Baron-Cohen, 1991a; Phillips, Baron-Cohen, & Rutter, 1995) understand desires earlier and more easily than beliefs. The second is that it may be possible to understand desires on the basis of nonverbal communication (e.g., pointing), whereas the understanding of beliefs is more likely to require verbal communication. Method Participants. The 22 children (13 girls and 9 boys) were drawn from two government-funded schools for deaf children, one in London and one in Bristol. The two schools shared a common teaching ethos and both served children with a range of socioeconomic backgrounds. The schools used TC in their teaching, which entailed the use of both British Sign Language (BSL) and Sign-Supported English, with the aim that the children should become bilingual in English and BSL. All children were audiologically diagnosed as being profoundly deaf: they had an average hearing loss of at least 96 decibels in the better ear and had become deaf prior to the onset of language acquisition. They all were described by their teachers as using BSL as their principal communication medium. Most came from hearing families, though detailed information about home background is not available. The mean age of the children was 9 years 8 months (range: 5;8 to 12;4). No subject had any known associated disabilities such as autism, mental retardation, uncorrected visual impairment, or cerebral palsy. Each was judged by their teachers to be within the normal range of intelligence. (Most of these judgments were based on the teachers' extensive observation of the children in a school setting. Some of the children had also been given standardized intelligence tests, but records of these were not available to the experimenters. Unfortunately, practical constraints also did not permit IQ_tests to be given to the children in this study.) Task design. All children carried out two tasks. Both tasks lent themselves to use with deaf children for the following reasons: they revolve around (a) simple vocabulary and (b) a storyline that is readily comprehensible and also, by virtue of the involvement of props, visually salient. Marble task. The materials were a female doll (40 cm high), a furry cloth dog (30 cm high), a basket with fabric cover, a square box with fitted lid, and a marble. The basic task was the same as that used by Peterson and Siegal (1995): Baron-Cohen et al.'s (1985) adaptation of Wimmer and Perner's (1983) Sally-Anne story-test of false-belief. The task begins like this: a doll hides a marble in a basket and then goes off for a walk. While she is gone, a second character appears, moves the marble from the basket to a box and then leaves. The first doll then returns to the scene and the child being tested is asked where this doll will look for

4 188 Journal of Deaf Studies and Deaf Education 2:3 Summer 1997 her marble. Two control questions are finally asked, which tap whether the child (a) has noted the marble's new location and (b) can recall its original hiding place. It was inappropriate to produce a sign-for-word translation of the experimental script devised by Baron-Cohen et al. (1985), but the content of this script was faithfully rendered in the BSL version used in the current experiment, as shown in the Appendix. Following the reasoning of Peterson and Siegal, a toy dog was substituted for the second doll of the classic Sally-Anne marble paradigm. Every time the dolls' names are used in a classic version, they must be fingerspelled, and Peterson and Siegal found this posed considerable difficulty for signing deaf children: it increased demands on both attention and memory and presumably put poor spellers at a disadvantage. Breakfast cereal task. The materials were a male doll (40 cm high), a mini-box of Rice Krispies (10 X 7 X 4 cm) with either Weetabix or nothing inside, and a mini-box of Weetabix (9 X 17 X 5 cm) with either Rice Krispies or nothing inside. The basic task was Baron-Cohen's (1991a) adaptation of an experiment developed by Harris et al. (1989). This is a story-test designed to tap children's understanding of false-belief and also their appreciation of beliefs and desires as causes of emotion. The story begins with two types of breakfast cereal being presented to a hungry doll, who likes one of the cereals but not the other. The child being tested is asked what the doll would feel happy or sad if presented with (a) one box, and (b) the other (desire test 1). The doll then leaves the scene and the subject discovers that one of the cereal boxes contains the normal contents of the other (preferred) box, while this other box is empty. The boxes are then resealed. When the doll returns, the subject is once again asked what the doll would feel if presented with either box (belief test). Finally, the subject watches as the surprising contents of each cereal box are revealed to the doll; the subject is then asked what the doll's emotions would now be if given either box (desire test 2). A faithful BSL translation of Baron-Cohen's (1991a) experimental script (for first desire test, belief test, and second desire test) was used. A retranslation of the tasks into English is given in the Appendix. Following Baron-Cohen (1991a), questions within each of the three tests were randomized to avoid any order effect of children preferring to respond "happy" before "sad" or vice versa. Memory questions were asked at the beginning and end of the experiment, in order to check whether each subject had noted and remembered which of the cereals the doll preferred. A partiality check was also made in order to establish that a subject's own preferences between the two cereals did not confound task performance: in the last question posed, each child was asked to sign which of the two they personally liked more. The preferences of the doll were varied across trials: half the children were told the doll liked Weetabix but disliked Rice Krispies; the other half were told the reverse. In either case the preferred cereal was located in the wrong box. Overall procedure. Each child was tested individually in an empty classroom in the school. They were seated across a low table from two women: the experimenter (LS) and a storyteller (KR). KR is profoundly deaf and fluent in BSL, the children's principal means of communicating. She has signing abilities beyond the Stage 3 level. Most teachers in British signing schools for the deaf would be expected to have reached Stage 2 (examining authority: Council for the Advancement of Communication with Deaf People). KR told the stories involved in each task to each child using BSL. Each step in the narrative was followed by illustrative enactment: LS manipulated the animate characters and KR moved all other props in accompaniment. In order to counter fatigue or practice effects, half the subjects were presented with the marble task before the breakfast cereal task, and for the other half the order was reversed. LS and KR independently recorded each child's responses and were in complete agreement. Children from the two schools did not differ in their performance: no significant differences were found on any task (Fisher's Exact in each case, p >.05, 2-tail test). This justified the pooling of data from the two schools in all analyses.

5 Understanding of Beliefs and Desires 189 Table 1 Success on belief and desire tasks (out of 20 children who took all tests) Passed control questions Failed at least one control question Total Succeeded on belief tasks Failed on belief tasks Succeeded on desire tasks Failed on desire tasks Results Of the 22 children given the marble task, 15 (67%) passed the control questions for the marble task, and 7 (33%) failed at least one of them. Omitting over a third of the children from the analysis could have seriously biased the results, so these children were included in the rest of the study. However, the "control failers" and "control passers" are separated in the table and in some of the analyses. A one-way analysis of variance (ANOVA) was carried out on the whole initial sample of 22 children with control question success (passed all controls versus failed some controls) as the grouping factor, and age as the dependent variable. This showed a significant effect, with children who passed all controls tending to be older than those who failed some controls The children in this study performed significantly better on the marble task than those deaf children studied by Peterson and Siegal (19/22 versus 9/26; x 2 = 13.13; df= \;p<.01). They also performed considerably better than Baron-Cohen et al.'s (1985) autistic children (19/22 versus 4/20; x 2 = 18.62; df = \;p<.01), while not differing significantly from their normal children (19/22 versus 23/27; X 2 = 0.014; df= \;p = not significant [NS]). Twenty out of 22 children passed the control questions on the breakfast task. The two who did not (aged 5;8 and 10;3) were not included in the rest of the study. Sixteen of the 20 remaining children passed both belief questions. All children who passed one belief question passed the other as well. There was no indication that a child's performance was influenced by his or her own preference between the two cereals: belief test pass-rates of subjectss whose preference coincided with that of the doll did not differ significantly from those of children with the opposite preference (or indeed from the combined performance of subjects who had the opposite preference to the doll and subjects who were indifferent) (Fisher's Exact, p >.05, 2-tail test). The breakfast task had not been previously administered to deaf children. The children in this study performed significantly better than the autistic children in Baron-Cohen's (1991a) study (16/20 versus 9/17; x 2 = 14.3; df= 1; p <.01) and similarly to the normal children in that study (16/20 versus 14/19; x 2 = 0.22; df=,!;/> = NS). However, the high success rate on the marble task may be misleading, as only one belief question was asked, whereas in many other studies, including that of Peterson and Siegal (1995), two questions were asked. This means that if the marble task were considered in isolation, children in this study might appear to have an artificially high success rate through chance alone. Therefore, in subsequent analyses, children were counted as successful on belief only if they passed the marble task belief question and both breakfast task belief questions. As shown in Table 1, 14 children passed all belief questions, and 6 failed some. No child failed all the belief questions in both tasks. A one-way ANOVA was carried out on the 20 children given the belief tasks with belief success (passed versus failed) as the grouping factor and age as the dependent variable. The effect failed to reach significance The overall rate of success on the belief task is 70%

6 190 Journal of Deaf Studies and Deaf Education 2:3 Summer 1997 as compared with 35% (9 out of 26) of Peterson and Siegal's group of deaf children of hearing parents. The difference between these percentages is significant ( X 2 = 5.65;#-=l;/><.05). In the breakfast task, the children were required to justify all their judgments (both for belief and for desire). Ninety-eight percent of all their justifications were correct: they referred (a) to the apparent (rather than actual) contents, (b) to the doll's desires (e.g., "he likes Weetabix"), or (c) in the belief test, to the doll's restricted knowledge ("he didn't see inside"). It could be argued that children should not be counted as having a true understanding of false belief unless they pass the control questions as well as the belief questions. In fact, the necessity for such a criterion is highly questionable, in view of the children's almost universal success in justifying their judgments. Nonetheless, it seemed worth investigating how the use of the most stringent possible criteria would affect results. Due to the substantial number of control failers, such criteria would reduce the number of successful children to 11. The success rate would thus be reduced to 55% (if we consider only the 20 children who received all tests) or even to 50% (if we consider the entire initial sample of 22 children). These figures are still considerably greater than the 35% for Peterson and^ Segal's children, but due to the relatively small sample sizes, the differences between the samples fail to reach significance if these criteria are employed. If we take the success rate in this sample as 11 out of 20 (55%), then x 2 (df= 1) = If we take it as 11 out of 22, then x 2 (df= 1) = Neither figure reaches significance. However, even at the lowest possible estimate of success rate on the belief task (50%), the children in this sample are still performing significantly better than Baron-Cohen's samples of autistic children This is true whether their performance is compared with Baron-Cohen, Leslie, and Frith's (1985) children in the two-question marble task (x 2 = 4.11; df= 1; p <.05), or with Baron-Cohen's (1991) children in the breakfast belief task (x 2 = 4.36; df= 1; p<.05). By contrast, the children in Peterson and Siegal's (1995) study did not differ significantly from the autistic children in Baron-Cohen's studies. All of the 20 children who were given the breakfast test passed both desire questions. This universal success made more detailed analyses (e.g., by age) unnecessary. This task had not previously been given to deaf children. The performance was considerably better than that of the autistic children in Baron-Cohen's (1991a) study (20/20 versus 9/18; x 2 = \2;df= l;p<.01). Comparisons with Baron-Cohen's (1991) normal children were inappropriate due to the near-universal success in both groups (20/20 versus 17/19). A Wilcoxon sign test was used to compare children's performance on the belief and desire tasks. They performed significantly better on the desire tasks [Wilcoxon statistic (6/20) = 0; p <.05]. Discussion The extent of the difference in false-belief understanding between deaf children in this study and those in Peterson and Siegal's (1995, 1996) studies depends somewhat on the stringency of the criteria used to determine false-belief understanding. However, even when stringent criteria are used, the children in this study did not appear to be as severely delayed as those in Peterson and Segal's (1995, 1996) studies. There are at least two ways of explaining the discrepancies between these results and those reported by Peterson and Siegal. First, it could be argued that the children included in this study have developed some theory of mind that children in the earlier study still lacked, possibly as the result of greater language exposure. Such an argument is consistent with the fact that the few deaf children of deaf parents (i.e., children who had been brought up in a rich conversational environment using sign language) in Peterson and Siegal's (1995, 1996) studies also showed unimpaired understanding of false belief. Moreover, when Clark, Schwanenflugel, and Everhart (1996) assessed the theory of mind of deaf adults (who had presumably had far greater language exposure than deaf children) by the rather different technique of asking them to classify cognitive verbs, they found no difference between deaf and hearing adults. At first sight, this argument may seem improbable, given that the conspicuous difference in pass-rates for the two samples is set against a background of highly comparable life circumstances. Specifically, language

7 Understanding of Beliefs and Desires 191 exposure is likely to have been very similar for the two groups, since (a) the majority of children had nonsigning parents, and (b) all four of the schools that children were drawn from schools that were described as using TC in teaching. In fact, the current sample might be expected to have had marginally less exposure to language, given their somewhat younger age (although age only offers a crude index of language exposure). However, it could still be that the English children had somewhat greater or earlier exposure to sign language than the Australian children. Moreover, some of the children on Peterson and Segal's study had been taught Sign-Supported English as a first medium of communication, whereas all the children in this study had been taught both BSL and Sign-Supported English, with BSL considered to be their primary communication medium. Despite the possibly greater initial difficulty of learning more than one communication system, BSL is a more "naturalistic" language, and as such may be more conducive to rapid early language acquisition, and to the ability to make use of any opportunities for conversation with members of the deaf community. An alternative explanation of the failure to replicate Peterson and Siegal's findings invokes the methodological differences between the two studies: perhaps the poor performance reported by the previous researchers was the result of their style of task delivery. Peterson and Siegal employed the following procedure: one hearing adult spoke the story and manipulated the props in accompaniment; after each stage in the narrative, an interpreter repeated the spoken statement just given and simultaneously offered a translation in signed English. This may be problematic on two counts. The first is that Peterson and Siegal state that their children were "selected on the basis that each child used sign language (signed English and or Auslan) as his or her principal communication medium" (p. 465). Children with Auslan as a first language would have been at a notable disadvantage when presented with a task in Sign-Supported English, and their failure to grasp that desires and beliefs had to be taken into account may reflect poor comprehension of lip-reading and signed English rather than a lack of theory of mind. In this study, the task was given in BSL, which was the children's principal communication medium (although they were also familiar with Sign-Supported English). The second is that the children's attention was divided in more than one way: children were confronted with one adult who spoke while performing with toys and a parroting second who simultaneously signed. Thus, the children not only varied their gaze between the face and hands of the adults in front of them, but also had to shift attention from one adult to the other throughout the experiment. Moreover, such a procedure would result in a relative lack of synchrony between story and actions. These problems may well have led to the children becoming distracted at crucial points: the effect of such distraction would likely be particularly strong for children who already had some difficulties with the language medium used in the experiment. In the current study, the telling of the story running through each task was a fully coherent process: each section of the narrative was conveyed just once and in the children's first language, namely BSL; the contribution of the two presenters was integrated and the performance of both was essential to the presentation. These factors may have led to better performance. Why was performance on the control questions apparently worse in this study than in Peterson and Siegal's (1995) study (and in many studies of normal and autistic children), despite relatively good performance on belief questions (and excellent performance on desire tasks)? There are at least two possible explanations. The first possible explanation is that the children in this study were a little younger on average than those in Peterson and Siegal's (1995) study. Relative to their normal peers, deaf children, and especially young deaf children, have particular problems fully comprehending the task perhaps because the task is more attention draining for deaf children, since for them it imposes continuous demand on a single sensory modality (i.e., vision). Consistent with the age effect on control-test success, children's attention spans tend to increase with age (e.g., Sigman, Cohen, Beckwith, & Robert, 1991). The second possible explanation is that the control questions may have posed particular problems for reasons unrelated to the understanding of mental states.

8 192 Journal of Deaf Studies and Deaf Education 2:3 Summer 1997 In particular, they referred to past situations and so required the children to override their likely response tendency to answer in terms of present states and instead to rely on memory. By contrast, the belief and desire questions dealt with present states. A related point is that it is possible that the children tested in the current study gave full consideration to the first (crucial) question, but when this was immediately followed by presentation of two further (control) questions, their attention and application rapidly fell off. This suggestion is perhaps more compelling because no new information, no more story, separates the three test questions: the first question is more likely to be accepted within the context of the interactive storytelling that has gone before; whereas the second and third questions are further removed from the storytelling phase, and in this sense offer less incentive for the subject to attend. This is not incompatible with the results cited by Peterson and Siegal (1995), on the basis of the assumption that their children were less engaged in understanding the story as a whole and more focused on understanding each verbal statement as it came. The latter hypothesis could be tested by varying the order of presentation of crucial and control questions and investigating whether children perform better on the control questions if these are presented first. This had not been done in this study for fear of biasing responses to the crucial questions. The importance of methodological factors does not necessarily reduce the deaf children's performance deficits to an artefact of the specialized testing situation. In many real-life situations as well, deaf children are likely to be exposed to suboptimal communicative contexts, which result in greater demands on their attentional and information-processing capacities than would a more "user-friendly" context. This may have considerable implications for deaf children's theory-of mind abilities in naturalistic situations, if insufficient attention is given to their communication needs. So to what extent does delayed exposure to conversation delay acquisition of theory of mind? The fact that these children performed better than Peterson and Siegal's children should not obscure the fact that they still performed less well than would be expected on the basis of their chronological age. Indeed, if extremely (probably excessively) stringent criteria for success are used, the differences between these children and those of Peterson and Segal (1995) ceased to be significant, though they continued to perform significantly better than Baron-Cohen's autistic children (Baron-Cohen et al, 1985; Baron-Cohen, 1991a). Even if one uses far less stringent criteria and treats the different belief tasks separately, the 80% success rate on the breakfast task is presumably lower than would be expected for this age range (though this assumption should be tested by giving the task to hearing children 7 years old and over). Thus, deaf children of hearing parents do appear to be somewhat, though not grossly, delayed in their ability to pass false-belief tasks. Their problems may be in comprehending the task as a whole, more than with false belief as such, given that they were as likely to fail control questions as belief questions. It must, however, be remembered that two children (both over 7, and one as old as 10; 10) failed the belief questions despite passing all control questions. By contrast, the children in this study appeared to have no problems in understanding desire. They performed perfectly on desire tests, whatever their age, and whether or not they passed all control questions (though it must be remembered that the two children who failed the breakfast test control questions were excluded from the study). The significant difference between performance on the belief and desire questions is intriguing. It may simply reflect differences in ease of task comprehension. It is, however, plausible that children with verbal communication difficulties do understand desire better than belief, because the former is more communicable by nonverbal means (e.g., pointing, other gestures, and facial expression). If this were the case, it would support the view that not only does communication experience play some role in the development of theory of mind, but different forms of communication experience have differential effects on different aspects of theory of mind. Further studies are needed if we are to gain a fuller understanding of the extent to which deaf children are delayed in theory-of-mind acquisition: severely delayed (as suggested by Peterson & Siegal, 1995), slightly delayed (as suggested by this study), or not delayed at all. It would clearly be desirable to carry out a

9 Understanding of Beliefs and Desires 193 study of deaf children aged 4 5 years. If these young deaf children fail to match the high pass-rates commonly achieved by hearing children of the same age, then language and conversation will be implicated in theory-of-mind development. Research attempting to clarify this point empirically will have to address several issues. The number of younger children who failed control questions in the current study highlights potential difficulties in testing 4- to 5-year-olds, and some modified experimental format, which reduces attentional demand, may be called for. For very young and/ or language-delayed children, even this may not be sufficient. The dilemma arises: if linguistic demands are greatly simplified (e.g., by use of predominantly nonverbal techniques and/or by removing demands for justifications), then the task may become less demanding in other ways, and no longer be comparable with standard theory-of-mind tasks. If linguistic demands are not simplified, then children with limited language may fail for reasons unconnected with theory of mind. Nonetheless, some attempt should be made to investigate younger deaf children. Future studies should also include language tests, to elucidate the relationship between language and theory-of-mind performance more precisely. Longitudinal studies would be particularly useful, both for investigating the possiblity of language ability "thresholds" for performance in theory-of-mind tasks and for investigating the extent to which the understanding of desire typically precedes the understanding of belief. Appendix Experimental Script for Marble Task Basket set up near left edge of table; box positioned far right. Female doll (Ann) held in middle. What's this?... wait for reply... basket. What's this?... matt for reply... box. What's this?... matt for reply... girl. Name Ann Ann likes playing marbles. Marble producedfromkr's pocket and that placed in Ann's hand. She's had enough... hides marble. Ann made to bend over basket as marble placed under the cover there. Ann leaves. Ann walkedfromtable. Time passes... dog. Dog brought to table. He's nosey... sniffs. Dog moved towards basket, cover removed. What's this?... wait for reply... marble. Dog and marble moved together over to box; marble hidden there. Dog leaves. Dog removedfromtable. Ssh! Ann doesn't know; don't tell Ann. Ann comes back. Ann brought to table. Belief She, marble looks where? Reality Marble now where? Memory First, marble put where? Experimental Script for Breakfast Cereal Task Male doll (Ben) sat on table with mini Weetabix box and mini Rice Krispies box. Preferences of the doll varied across trials: half the subjects told Ben liked Weetabix but disliked Rice Krispies (as scripted below); other half told the reverse. Contents of the boxes adjusted accordingly. Desire Test 1 What's this?... wait for reply... boy. Name Ben He wakes up, goes downstairs, is hungry. What's this?... maitfor reply, e.g., subjectfingerspells W.. E.., etc., or shrugs to say sign not known... Weetabix. He likes Weetabix. What's this?... wait for reply... Rice Krispies. He doesn't like Rice Krispies. Memory 1 He likes which? Pointing to boxes. Give THIS box. Weetabix box moved towards Ben. Desire 1 Ben feels what? Prompt usually needed. Happy or sad? Why? Give THIS box. Rice Krispies box moved towards Ben. Desire 2 Ben feels what? Why? Belief Test Ben leaves. Ben walkedfrom table Look inside this (Weetabix box). Yes open i t... noth-

10 194 Journal of Deaf Studies and Deaf Education 2:3 Summer 1997 ing!... Ssh! close it up. Look inside this (Rice Krispies box). What?... Weetabix!... Ssh! close it up. Boxes replaced on table as before, only their positions swapped. Ben doesn't know; don't tell Ben. Ben comes back. Ben brought back to table. He has not opened this or this. Belief 1 Ben sees this (Weetabix box) feels what? Why? Belief 2 Ben sees this (Rice Krispies box) feels what? Why? Desire Test 2 Give Ben THIS box (Weetabix). Open it. Box opened and given to doll. Desire 3 Ben feels what? Why? Give Ben THIS box (Rice Krispies.) Open it. Box opened and given to doll. Desire 4 Ben feels what? Why? Final Checks Preference You like which? Subject signs "Weetabix" or "Rice Krispies." Memory 2 Ben likes which? References Baron-Cohen, S. (1989). Perceptual role taking and protodeclarative pointing in autism. British Journal of Developmental Psychology, 7, Baron-Cohen, S. (1991a). Do people with autism understand what causes emotion? Child Development, 62, Baron-Cohen, S. (1991b). Precursors to a theory of mind: understanding attention in others, In A. Whiten (Ed.), Natural theories of minds: evolution, development and simulation of everyday mindreading (pp Oxford: Blackwell. Baron-Cohen, S. (1993). From attention-goal psychology to belief-desire psychology: The development of a theory of mind and its dysfunction. In S. Baron-Cohen, H. Tager- Flusberg, and D. J. Cohen (Eds.). Understanding other minds: perspectives from autism (pp ). Oxford: Oxford University Press. Baron-Cohen, S. (1994). How to build a baby that can read minds: Cognitive mechanisms in mindreiding. Cahiers de Psychologic Cognitive/ Current Psychology of Cognition, 13, Baron-Cohen, S., Leslie, A. M., & Frith, U. (1985). Does the autistic child have a 'theory of mind'? Cognition, 21, Baron-Cohen, S., Campbell, R., Karmiloff-Smith, A., Grant, J., & Walker, J. (1995). Are children with autism blind to the mentalistic significance of the eyes? British Journal of Developmental Psychology, 13, Baron-Cohen, S., Cox, A., Baird, G., Sweetenham, J., Nightingale, N., Morgan, K., Drew, A., & Charman, T. (19%). Psychological markers in the detection of autism in infancy in a large population. British Journal ofpsychiatry, 168, Campbell, R. (1994). How to build a model that works. Cahiers de Psychologic Cognitive/Current Psychology of Cognition, 13, Chandler, M, Fritz, A. S., & Hala, S. (1989). Small-scale deceit: Deception as a marker of 2-year-olds', 3-year-olds' and 4- year-olds' early theories of mind. Child Development, 60, Clark, J. (1990). Investigating the use of theory of mind tasks in naturalistic settings by children of 4, 5, and 6 years old. University of Oxford: Undergraduate research project (supervised by Stephen Milan). dark, M. D, Schwanenflugel, P. J., & Everhart, V. S. (1996). Theory of mind in deaf adults and the organisation of verbs of knowing. Journal of Deaf Studies and Deaf Education, 1, dements, W. A., & Perner, J. (1994). Implicit understanding of belief. Cognitive Development, 9, Fletcher, P. C, Happe, F, Frith, U, Baker, S. C, Dolan, R. J, Frackowiack, R. S. J., & Frith, C D. (1995). Other minds in the brain: A functional imaging study of theory of mind in story comprehension. Cognition, 57, Gray, C. D, & Hosie, J. (19%). Deafness, story understanding and theory of mind. Journal ofdeaf Studies and Deaf Education, 1, Happe, F. G. E. (1995). The role of age and verbal ability in the theory of mind task performance of subjects with autism. Child Development, 66, Harris, M. (1992). Language experience and early language development. Hove: Erlbaum Associates. Harris, P. L., Johnson, C N., Hutton, D, Andrews, G, & Cooke T. (1989). Young children's theory of mind and emotion. Cognition and Emotion, 3, Hermelin, B., & O'Connor, N. (1978). Seeing and hearing and space and time. London: Academic Press. Jenkins, J. M., & Astington, J. W. (1996).Cognitive factors and family structure associated with theory of mind development in young children. Developmental Psychology, 32, Leslie, A. M. (1987). Pretense and representation: The origins of'theory of mind'. Psychological Review, 94, Leslie, A. M. (1994). Pretending and believing: Issues in the ToMM. Cognition, SO, Leslie, A. M., & Frith, U. (1988). Autistic children's understanding of seeing, knowing and believing. British Journal of Developmental Psychology, 6, Marschark, M. (1993). Psychological development of deaf children. New York: Oxford University Press. McAlpine, L. M., & Moore, C L. (1995). The development of social understanding in children with visual impairments. Journal of Visual Impairment and Blindness, 89,

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