Atypical Theory of Mind in Children with Autism and Their Siblings

Background: The ability to understand and reason about people’s mental states, known as Theory of Mind (ToM), is impaired in individuals with Autism Spectrum Disorders (ASD). To test ToM in children, Wellman & Liu (2004) developed a five-item scale of ToM and showed that in typical children, ToM development involves progressive acquisitions of mental-state concepts, in the following order: Not-Own-Desire (NOD, others can have a different desire than one’s own), Not-Own-Belief (NOB, others can have a different belief than one’s own), Knowledge Access (KA, someone without perceptual access to an object will not know the identity of the object), Content False Belief (CFB, people can hold a belief that is incorrect and in contrast to reality) and Real Apparent Emotions (RAE, people can hide their emotions, expressing an external emotion that does not match their internal emotion).  By comparison, children with ASD show significant deficits and delays on these ToM tasks, and most interesting, progress in an atypical reversal of the last two categories, i.e., NOD, NOB, KA, RAE, CFB, (Peterson, Wellman, and Liu, 2005).

Objectives: The current study extended these previous studies by examining the sequence of ToM development in both children with ASD and their unaffected siblings, as a way of determining whether ToM deficits are part of the broader autism phenotype (BAP) early in development. To this end, we tested children with ASD, their siblings, and typically-developing control children on the 5-item ToM scales.

Methods: Our sample included three groups of 4- to 6-year-olds: children with ASD (n = 12); children without ASD who had an older sibling with ASD (SIBS) (n = 12); and typically-developing children (TD) from families with no history of ASD (n = 24).  For each subject, we ran two trials of each of the 5-item ToM scales. The two trials had the same item structure and scenario with different story characters, objects, and locations.  Each item could result in a score of 0 (neither trial correct), 1 (one trial correct), or 2 (both trials correct). Data were analyzed using mixed-design 2-factor ANOVAs (2 subject groups: ASD vs. TD and SIBS vs. TD, and 5 ToM tasks: NOD, NOB, KA, CFB, RAE).

Results: For all three subject groups, performance varied with task item (main effect of task: p<0.001).  However, subject groups differed in two important ways.  First, both the ASD and the SIBS groups exhibited worse overall performance than the TD group (main effect of subject group: ASD vs. TD: p=0.024, SIBS vs. TD: p=0.039).  Second, whereas both the TD and SIBS groups followed the pattern of NOD=NOB=KA³CFB>RAE, ASD children exhibited a significantly different pattern: NOD=NOB>KA=RAE³CFB. 

Conclusions: By 4 to 6 years of age, both children with ASD and their unaffected siblings show significant deficits in ToM skills, suggesting that ToM impairments are part of the BAP early in development.  However, the nature of the impairment differs between ASD children and unaffected siblings, in that only children with ASD show an atypical progressive acquisition of mental-state concepts. Supported by HD052804.