A and B. The behaviour of eight rhesus monkeys during the first six months of life was studied. The animals were brought up by their natural mothers living in captivity in small social groups containing one adult male and three or four adult females.
C (i). Three births were witnessed. The placenta was not eaten in some cases.
C (ii). Many of the mothers held their babies in abnormal positions immediately after birth. They were often held so tightly that they could not turn their heads to gain the nipple.
D (i)The normal ventro-ventral nursing position is described.
D (ii)The methods by which the infant finds the nipple are described. The time spent by the infant on the nipple with its eyes open rose to a peak of 35 per cent in the third week, and then declined (Fig. 1). Only a small proportion of the time spent on the nipple is occupied by sucking.
D (iii). A nipple preference is established during the first few weeks. This may not be a sucking preference.
D (iv). The proportion of time in which the infant's eyes were closed fell from 70 per cent in week 1 to about 25 per cent after five weeks, and then more slowly (Fig. 2). The proportion of time on the mother with the eyes open but not attached to the nipple rose to a peak of 22 per cent in weeks 7/8 (Fig. 3).
D (v). The way in which the mother carried the baby during locomotion is described. Riding on the mother's back was not common in our colony.
D (vi). Some observations on the development of eye-hand-mouth coordination are described. The ages at which certain criteria of achievement were reached are given in Table 3.
D (vii). The initiative for the first separation between mother and infant comes sometimes from the mother, sometimes from the infant.
D (viii). The proportion of time spent off the mother rose t o about 60 per cent after 16 weeks (Fig. 4).
D (ix). The ages at which certain criteria of achievement were attained are given in Table 4.
D (x). The manner in which the infant follows its mother is described.
D (xi). As the infants get older, the length of the periods which they spend off their mother increases (Fig. 5). After the sixth week the infant spends a considerable proportion of its time more than two feet from its mother (Figs. 6, 7 & 8).
D (xii). The relative roles of infant and mother in increasing and decreasing the distance between them are shown in Figs. 9 and 10.
D (xiii).The manner in which the mother protects and grooms the infant is described
D (xiv). The development of independent feeding is described. (Fig. 11). She also shows various types of “affectionate” behaviour without obvious function.
D (xv). As the infant gets older, there are a number of contexts in which its behaviour is not reciprocal to that of the mother. Mother-infant incompatibility arises in the The development of independent feeding is described contexts of sucking, carrying, feeding, exploration and play.