VISUAL OBSERVING BY RHESUS-MONKEYS - SOME RELATIONSHIPS WITH SOCIAL-DOMINANCE RANK

Rhesus monkeys [5 Macaca mulatta] were tested in a visual exploration situation to determine whether the mean frequency or mean duration of visual observing were systematically related to the dominance status of the observing animal. A dominance hierarchy among the 5 subjects was first determined by means of a competitive food-getting task. Following dominance testing, visual exploration testing was begun. All subjects were permitted to observe all other subjects in a round-robin pairing system involving 2 animals at a time. In each pairing, one animal served as the experimental subject (observer); the other as the stimulus (visual incentive). A highly significant linear effect of dominance was found in regard to duration of observing. Subjects high in the dominance hierarchy observed for significantly shorter durations than low-dominant subjects. Significant effects of dominance on the frequency of observing were also found, with animals intermediate in the hierarchy viewing more frequently than animals at either extreme. The data were interpreted in terms of the arousal and reduction of fear as a function of dominance and also through the notion of dominance distance.