We investigated the relationship between age and laughing and smiling in children with Angelman syndrome. Twenty-four children with Angelman syndrome were exposed to three experimentally manipulated conditions: proximity only, restricted social interaction, and social interaction. Children smiled the most in the social interaction condition and the least in the proximity only condition confirming the effect of social interaction on these behaviors. There was a decline in smiling and laughing in the oldest group (13.4-15.9 years) only in the social interaction condition. This trajectory of a decline in resource soliciting behaviors with age is consistent with predictions based on kinship theory. © 2011 Wiley-Liss, Inc.