The Development of Maternal and Infant Behavior in the Rhesus Monkey

Abstract

This study traced the development of maternal behavior in a group of four adult rhesus female monkeys, and compared the development of the behavior of their infants with the development of the behavior of infant monkeys raised on cloth surrogate mothers. The two groups of subjects were housed, and their behaviors observed, in separate playpen situations. Social interactions in pairs and subsequently in groups of four infants were observed for the first 15 months of the infant's development. The recorded data placed a primary emphasis on social behaviors and their development, although additional aspects of infantile behaviors were measured. Two stages in the expression of maternal behavior were demarcated: a stage of maternal attachment and protection which was characterized by intensive infant-mother contact and maternal care-giving behaviors; and a transitional stage characterized by the fact that the care-giving behaviors decreased and negative responsiveness gradually increased. Comparisons of the mother-raised and surrogate-raised infants premitted an assessment of the influence of maternal responsiveness on infant behaviors. Maternal behaviors played an important role in influencing infantile behaviors early in life by orienting the infant toward and maintaining the infant in contact with the mother's ventral surface. Also, with the development of the transitional stage, the real mothers played a noteworthy part in the emancipation of their infants severing the intense early physical manifestations of the infant-mother tie. As the strength of the mother-infant and infant-mother affectional systems diminished, manifestations of the infant-infant affectional system appeared and developed, and infant-infant interactions within groups were observed. These data generally indicated a greater degree of social sophistication on the part of the real mother-raised infants. The surrogate-raised infants were less socially oriented or socially aware of other infants, and exhibited a greater degree of social ineptitude as well as a lack of social organization in their early interactions. Most of the between-group differences were restricted to the first half of the 15 month period of development covered by this study and these differences tended to disappear as a function of time. This was attributed to the compensatory capabilities of intensive infant-infant interaction to override and cancel out the inept social responding imparted by inadequate "mothers".