OLD, SOCIALLY HOUSED RHESUS-MONKEYS MANIPULATE OBJECTS

Recent research has indicated that old, individually housed monkeys sh ow little interest in novel objects. Yet unanswered is whether this ef fect is caused primarily by age or housing condition. The purpose of t his study was to assess the role of social living in promoting respons iveness to objects. We measured the rates of object manipulation in ol der animals, assessed responsiveness over time to particular objects a s a measure of habituation, and examined social influences on object u se. Several social groups of rhesus monkeys that contained older adult s were studied. These groups were housed in indoor pens or in an outdo or enclosure, and all monkeys had continuous access to a variety of ob jects in their home environment. In contrast to previous studies of in dividually housed monkeys, our group-housed monkeys showed sustained i nterest in objects. Old monkeys manipulated objects extensively, and t his response was all the more significant, given that the objects were not novel. Monkeys housed in an outdoor enclosure showed object manip ulation patterns that were not different from monkeys housed in indoor pens. However, females exhibited much higher object-related responses than males. Social facilitation played a role in the reactions of som e monkeys to objects. Patterns of social facilitation as well as avoid ance were present in two of the three indoor groups that were observed . Failure to manipulate objects in rhesus macaques appears to be more a function of individual housing than of old age. Factors such as envi ronmental complexity, social needs, and early experience should be con sidered in order to understand why individually housed rhesus monkeys are unresponsive to objects.