A hallmark symptom of autism is rigidity, or difficulty in adapting to changing environments. This adaptive ability is also known as cognitive flexibility. The present study will examine the association between cognitive flexibility, pathways of neural activity, and a particular autism-linked gene, 5-HTTLPR, which is involved in signaling by the neurotransmitter serotonin. Using functional magnetic resonance imaging (fMRI), the predoctoral fellow will test the hypothesis that variation in the 5-HTTLPR gene is related to rigidity symptoms. She will use fMRI to look at the patterns of neural activity while ASD individuals perform a task measuring cognitive flexibility. The subjects will include people with multiple different alleles of the 5-HTTPLPR gene. This will determine whether different 5-HTTLPR genotypes are associated with abnormal brain activation patterns during cognitive flexibility tasks or with the severity of rigidity symptoms. This research may identify genetically influenced neural and cognitive abnormalities affecting cognitive flexibility that could potentially be targeted by therapies to alleviate symptoms of rigidity.