The cerebellum and inferior olive are two brain areas consistently shown to be abnormal in neurobiological and post-mortem anatomical studies in autism. The inferior olive (IO), part of the brainstem-cerebellar system, integrates sensory and motor activity before relaying it to the cerebellum. Of particular interest in autism spectrum disorder (ASD) is the fact that the IO is a pacemaker system that may play a global role in brain timing that is important for language functioning. Eyeblink conditioning is an associative learning task that requires normal functioning of the IO and the cerebellum and is a sensitive, non-invasive measure of brain timing. This study will test the general hypothesis that children with ASD are impaired in rapid temporal processing and will show deficits in eyeblink conditioning. The study will involve 40 patients with ASD (aged 6 to 18 years) and 40 matched controls. Data obtained from this study will be used to devise larger and more definitive studies in ASD and as a tool to guide mechanistic studies in animals. Eyeblink conditioning could have a number of uses, including as a measure for early detection of ASD, as a tool for translational research, and as an outcome measure for treatment studies.