Autism is a developmental disorder involving qualitative impairments in social interaction. One source of those impairments are difficulties creating facial expressions of emotion. Difficulties with facial expressions may arise from deficits in a motivation to express positive emotions with others. The difficulties may also stem from physiological problems in physically creating expressions that are due to damage to areas of the brain that control the facial nerve (which produces those expressions). This project will utilize automated facial analysis software to compare how, when, and to what extent 20 four- to six year-old children with autistic disorder, 20 children with developmental disabilities, and 20 typically developing children produce facial expressions. Children will be observed playing social games with a tester and in a non-interactive context watching video clips and playing simple video games. These methods will provide insight in to the nature and possible source of the facial expressivity deficits expected in children with autism. If deficits are evident in an interaction setting but not when playing with video games, this would suggest deficits are related to an emotional motivation to engage. If deficits are apparent in both settings or are evenly distributed between positive, negative, and neutral expressive periods, this would suggest deficits are due to a physiological deficit. What this means for people with autism: Discerning the probable source of difficulties in facial expressivity will provide a more complete understanding of social deficits in autism and suggest therapeutic approaches that are most appropriate for children with autism.