The behavioral and heart rate responses of 22 children with autism and 22 children with other developmental disabilities were compared whilst they were watching videotapes of a baby either playing or crying. We expected both groups to show arousal as increased heart rate when watching the video of the crying baby, and the children with autism to attend less than the other children to both videos. However, the children with autism were as attentive to the videos as the other children, and both groups showed heart rate slowing compared with a baseline condition. There was no change in heart rate during interactions with a stranger or separation from mothers. The findings suggest that the lack of social attention often demonstrated by children with autism does not stem from increased arousal in social situations. An alternative explanation is considered.