Changes in the rhesus mother-infant relationship through the first four months of life

Measurements of the course of interactions between rhesus monkey infants (Macaca mulatta) and their mothers during the infant's first 16 weeks showed changes in the tendencies of both partners to be together and apart. Referring only to the partner who was primarily responsible for an age-related change, by using a single index of responsibility for contact or proximity, was found to be an oversimplification. Maternal rejecting behaviour may have been primarily responsible for changes in the time spent apart only during the first 6 weeks. After the infants' sixth week, both partners' tendencies to be apart increased together. Infants then began to spend longer away partly to interact with social companions other than their mother. Mothers restricted and followed their infants more up to week 4, but after week 8 decreases in these measures allowed infants to spend longer away. Similarities between the time courses of the time spent apart from their mothers by rhesus infants in this study and in field studies are pointed out. The similarities seem striking partly because differences between studies that do not use confidence intervals (or standard errors) cannot be shown easily. Conflict between parent and infant occurred, but how it appears, and how significant it is in each species at each infant age, remains to be discovered.