Positive social reinforecement in the nursery school peer group.
D000367:Age Factors; D000704:Analysis of Variance; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007398:Interpersonal Relations; D008297:Male; D008722:Methods; D010379:Peer Group; D010988:Play and Playthings; D012054:Reinforcement, Psychology; D012578:Schools, Nursery; D012737:Sex Factors