Abstract
Impairment in social interaction is a core feature of autism spectrum disorder (ASD), but the factors which contribute to this social skill deficiency are poorly understood. Previous research has shown that cognitive ability can impact social skill development in ASD. Yet, children with ASD whose cognitive abilities are in the normal range nevertheless demonstrate deficits in social skill. More recently, the social motivation theory of ASD has emerged as a framework by which to understand how failure to seek social experiences may lead to social skill deficits. This study was designed to better understand the relationships between cognitive ability, social motivation, and social skill in a well-characterized cohort of children with ASD (n = 79), their unaffected siblings (n = 50), and unrelated neurotypical controls (n = 60). The following instruments were used: The Stanford-Binet intelligence quotient (IQ), the Social Responsiveness Scale's Social Motivation Subscale, and the Vineland Adaptive Behavior Scales' Socialization Standard Score. We found that lower cognitive ability contributed to diminished social skill, but did so universally in all children. In contrast, social motivation strongly predicted social skill only in children with ASD, such that those with the lowest social motivation exhibited the greatest social skill impairment. Notably, this relationship was observed across a large range of intellectual ability but was most pronounced in those with IQs ≥ 80. These findings establish a unique link between social motivation and social skill in ASD and support the hypothesis that low social motivation may impair social skill acquisition in this disorder, particularly in children without intellectual disability. LAY SUMMARY: The relationships between cognitive ability, social motivation, and social skill are poorly understood. Here we report that cognitive ability predicts social skill in all children, whereas social motivation predicts social skill only in children with autism. These results establish a unique link between social motivation and social skill in autism, and suggest that low social motivation may impair social skill acquisition in this disorder, particularly in those without intellectual disability.