title: From egocentric to cooperative play in young children. A normative study.
mesh_terms: D002657:Child Development; D002675:Child, Preschool; D003299:Cooperative Behavior; D003674:Defense Mechanisms; D004532:Ego; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009769:Object Attachment; D010379:Peer Group; D010988:Play and Playthings; D012919:Social Behavior