The game of peek-a-boo.
D001321:Autistic Disorder / Q000628:therapy; D002654:Child Care; D002675:Child, Preschool; D003643:Death; D005239:Fear; D006801:Humans; D007223:Infant; D007224:Infant Care; D010287:Parent-Child Relations; D010988:Play and Playthings; D012649:Self Concept