The effect of a manipulatory incentive on social interactions of rhesus monkeys

Abstract

Experimental tests of social dominance in pairs of rhesus monkeys have almost invariably used competitive food-getting situations to determine dominance status . Although a few of these studies (Hamilton, 1960 ; Miller & Murphy, 1956) have reported incidences of friendly behaviour (e.g . grooming and huddling) during dominance testing, it is not clear whether such interactions occur during presentations of the food incentive or only between presentations . Presumably, as soon as one of the animals consumes the incentive the competitive situation is terminated-allowing for only a brief competitive interaction . If, however, a situation was designed in which the element of competition was persistent, it would then be possible to study and directly compare continuous competitive social interactions with interactions during non-competitive conditions . It has been shown that manipulatory objects are effective incentives for rhesus monkeys (Harlow, Harlow & Meyer, 1950) and it seems reasonable that such objects could serve as incentives in competitive test situations . The purpose of the present study was to determine whether a manipulatory object would have any effect on the social interactions of young rhesus monkeys. More specifically, a piece of rope was introduced into the home cage of a pair of rhesus monkeys to determine whether there was any change in the form and frequency of social responses from that of the normal social activity shown by the pairs. The length of the rope was varied to determine the effect of this variable on competitive interaction .