Modification of the response to separation in the infant rhesus macaque through manipulation of the environment.

Rhesus mother-infant pairs were housed in a playpen apparatus beginning just before the birth of four male infants. The infants were separated from their mothers four times beginning at a mean age of 218 days. In Type A separations (I and IV) the infants were removed and housed away from their familiar environment in a protected setting; in Type B separations (II and III) the infants remained in the familiar setting and mothers were removed. One pair was separated every 2 weeks for 6 days; for a particular infant, a mean of 8 weeks intervened between each of the separations. On the basis of infant behavior during separation. Type B separations appeared to have a more deleterious effect on the infant: infants did not show the typical behavioral signs of depression under Type A housing conditions, whereas, under Type B conditions, infants expressed the typical depressive reaction to separation. However, comparisons of pre- and postseparation behaviors in the mother-infant pairs indicated that Type A separations were more perturbing. Increases in ventral-ventral contact between mothers and infants were greater following Type A separations and increases in time at nipple occurred only after Type A separations; infant grooming by mother increased only after the first, a Type A, separation. Type B separations may have affected mothers more severely in that reciprocity between maternal cradling and infant clinging was greater following Type B separations than following Type A separations when infants clung significantly more often than mother cradled.