Perceptual activity and concept attainment.
D000367:Age Factors; D000704:Analysis of Variance; D002648:Child; D002657:Child Development; D002675:Child, Preschool; D003071:Cognition; D003210:Concept Formation; D004192:Discrimination, Psychological; D005106:Exploratory Behavior; D005260:Female; D006801:Humans; D007804:Language Development; D008297:Male; D010465:Perception; D014796:Visual Perception