Although IQ varies widely among people with autism, researchers have yet to figure out what causes this variation. However, several lines of research have found abnormalities in the area of the brain called the corpus callosum in people with autism and preliminary findings from Dr. Lainhart's laboratory indicate that these abnormalities may be related to IQ in people with autism. This study will expand on that preliminary work, using anatomical magnetic resonance imaging (aMRI) and diffusion tensor MRI to measure brain volume and the integrity and strength of the connections between nerve cells in the corpus callosum. Pre-doctoral fellow Molly DuBray, who brings to the fellowship strong experience in statistics and previous work with brain imaging, will compare data from a large number of individuals with autism and those who are not affected. In the process of this study, What this means for people with autism: Findings of a relationship between abnormalities in the corpus callosum and cognitive behavior in people with autism could suggest new treatments that help strengthen the connections in this brain area.