Factors related to performance failure on executive tasks in autism

Persons with autism may have particular difficulty on tasks that require a great degree of interplay and plasticity of inhibitory and switching processes, such as new tasks with poorly defined rules. We chose five executive function tests with varying degrees of rule constraint to assess the flexibility of selective inhibition/switching abilities in subjects with autism. Nineteen high-functioning (IQ > 85) subjects with autism and 16 controls of average psychometric intelligence were matched for age and socioeconomic status (SES). The results showed that (a) the level of performance of subjects with autism was significantly lower than that of controls on all executive tasks and was characterized by perseverative 'stuck-in-set' errors; (b) the error rates (in particular, perseverative ones) increased on tasks with lower rule constraints for the subjects with autism but not for control subjects; and (c) the level of performance on executive tasks appeared generally independent of psychometric intelligence level. Our data suggest that the failure of executive functioning in autistic subjects may be attributed primarily to a deficit in disengagement. Poor governing of selective inhibition resources is evidenced in escalating perseverative behaviors for subjects with autism on tasks with a low degree of rule constraint.