A hallmark symptom of autism is rigidity, or difficulty in adapting to changing environments. This adaptive ability is also known as cognitive flexibility. In autistic individuals, brain regions which control cognitive flexibility may be abnormal, but research has yet to directly link abnormal activity in these brain regions to rigidity symptoms. Rigidity symptoms may also have a genetic component, as genetic variation could affect cognitive flexibility and brain function. Genes linked to autism are candidates for being involved in these processes. 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.