Problems with motor function are prominent in autism spectrum disorder (ASD), but may differ greatly from person to person. While motor problems can clearly affect daily function, they may also affect social function and may contribute to difficulty learning social skills during early childhood. This novel system for imaging natural movement and brain activity at the same time will allow identification of underlying similarities across different impaired movements. Twenty five ASD adolescents (aged 12-16) and 25 typically developing age- and IQ-matched controls will be tested, and the timing, accuracy, and efficiency of natural full body motion during self-initiated and directed movement will be measured. An EEG will also be recorded simultaneously. Isolating specific underlying mechanisms that lead to a variety of motor impairments (e.g., timing, anticipation) will inform effective intervention that may in turn improve not only motor competence but also behavioral problems that are affected by motor dysfunction.