Comparative reinforcing effect of eight stimulations on the smiling response of infants.
D002652:Child Behavior; D005149:Facial Expression; D005260:Female; D006309:Hearing; D006801:Humans; D007223:Infant; D007699:Kinesthesis; D007858:Learning; D008297:Male; D012054:Reinforcement, Psychology; D013997:Time Factors; D014110:Touch; D014785:Vision, Ocular