The Influence of Typical Siblings On the Social-Communicative Behaviour and Theory of Mind Development in Children with Autism

Background: Research indicates that having siblings is positively associated with theory of mind (ToM) in typically developing (TD) children. Initially older but not younger siblings were found to facilitate ToM development (Ruffman et al., 1998) but when only child aged siblings (12 months to twelve years) were involved younger siblings also showed superior ToM skills to only children (Peterson, 2000). Social and communication impairments are core features of autism and ToM is also usually severely delayed. We previously found that although there was a small advantage in having a younger sibling, having an older sibling was a disadvantage for ToM development in children with ASD (O’Brien, Slaughter & Peterson, 2011) but no research has directly observed siblings playing together to explore the extent to which siblings of children with autism engage in interactions likely to facilitate ToM. Objectives: We conducted the present study to directly examine how the presence of older and younger siblings is associated with ToM development and intentional communication by observing social-communicative behaviour and the different roles and forms and functions ASD children take when playing with older sibs compared with younger sibs. Methods: Participants were 24 dyads (12 older sibs and 12 younger sibs) of a child with an ASD (mean age=7.45 SD=2.50) and a child aged TD sibling (mean age=8.12 SD=3.99). The siblings were screened with the SCQ to rule out ASDs. All children completed a standard battery of ToM tasks, and the PPVT-III. ASD children were also assessed with the ADOS and VABS-II. Each sibling dyad played for 10 minutes in a free play session which was video-taped and coded using the coding scheme from the modified-classroom observation schedule (M-COSMIC) which was created to measure intentional communication (Clifford et al., 2010). Results: ToM and VMA were significantly better in ASD sibs with younger sibs compared with older sibs. ASD children in younger sibling dyads showed significantly more communicative-social behaviours than in older sibling dyads. A non-parametric (spearman) correlation found ToM was significantly correlated (p<.01) with age and VMA as well as the M-COSMIC categories of showing off/attention, shared attention, initiation and use of three word plus phases and negatively correlated with non-interaction/no response. Conclusions: Younger TD siblings of children with autism confer a benefit in ToM development and intentional communication. It is possible older siblings over compensate for their ASD sibling which may limit the effect of ToM development and the social learning of the ASD children. These finding could be used to create interventions involving siblings to improve theory of mind and intentional communication in ASD children. It may involve promoting play with younger siblings and teaching older siblings to not compensate for their ASD siblings.