Why do American infants have a greater amount of vocalization, and particularly of happy vocalization, than do Japanese infants? To answer this question, 30 Japanese and 30 American first-born, 3- to 4-month old infants equally divided by sex, and living in intact middle class urban families were observed in their homes on two consecutive days during 1961-1964. Two specific styles of child care were shown to be at work influencing the process by which learning of cultural expectations for behavior comes about. American mothers were busier, livelier, and differentiated in their response to their baby's happy or unhappy vocalizations. The Japanese mother's pace was more leisurely. She was more attentive to the baby when he was going to sleep or waking up and less responsive to vocalization in general. Apparently, these differences in maternal style of child care elicit behaviors from infants that are in line with later expectancies for behavior in the two cultures. A followup study of the first 20 of these same children in each culture as they became 2 1/2 and 6 years of age is being completed. It is expected that the early differences in behavior seen in infancy will continue along the lines laid down by the two cultures. [Not available in hard copy due to marginal legibility of original document.] (WY)