What is the relationship between cognitive flexibility and insistence on sameness behaviour in autism?

Background: Recent evidence suggests that domains of autistic impairment often occur independently, in the absence of other elements of the syndrome. This raises the possibility that autism is a disorder of multiple underlying impairments, not explicable by one underlying abnormality. Particular impairments may be associated with specific behavioural domains. One domain of interest is ‘Insistence on Sameness’, an empirically derived, heritable dimension that is a component of the repetitive, stereotyped behaviour element of the autism triad. It has been suggested that executive function difficulties underlie some of the repetitive interests and behaviours seen in autism.

Objectives: We aimed to investigate whether cognitive inflexibility was associated with one specific element of autistic behaviour, insistence on sameness (IS), but not with the other elements of the syndrome.  In a general sense, we aimed to test a ‘multiple underlying impairments’ model of autism.

Methods: Cognitive inflexibility was measured using three tests of set-shifting (The Wisconsin Card Sort Test, the California Trail Making Test and the Intradimensional/Extradimensional Shift Task) in a sample of 46 young people with an autism spectrum disorder and a verbal IQ in the normal range. IS was measured using a parent-report questionnaire, the Repetitive Behaviour Scale – Revised, and social-communication impairment was quantified using the 3Di, a comprehensive, semi-structured parent interview.

Results: No correlation was found between IS and social-communication impairments. One set-shifting measure (trail making) showed a moderate correlation with IS in the direction predicted when a one-tailed test was used. There was no relationship between this measure of set-shifting and social-communication impairment.

Conclusions: These findings suggest that cognitive inflexibility is associated with greater IS in children with an ASD, but not with social-communication impairments. They offer support for the idea that the social-communication and repetitive behaviour components of autism may represent separate dimensions with distinct underlying susceptibilities.