Visual cues for attention following in rhesus monkeys

It is now well established that great apes follow human gaze direction. Despite physiological evidence showing cells in macaque temporal cortex sensitive to direction of eye gaze, there has been little evidence in non-ape species of similar abilities. The aim of this study was to investigate, at a behavioural level, whether monkeys can use static gaze, head, and body cues of conspecifics to interpret the direction of attention of others. We recorded the looking behaviour of 2 rhesus monkeys elicited by the presentation of photographs of conspecifics directing their attention in space. With photos of monkey stimuli whose head and body were oriented in different or similar directions, we found that the head but not the body was used by the monkey subjects to orient their own attention. With photos of monkey faces oriented to the camera while gaze was averted left, right, up or down, we demonstrated that monkeys are able to spontaneously follow gaze of conspecifics. With photos of monkey heads oriented 45 degrees to the right or left, attention following was stronger when the gaze direction was consistent with the head orientation than when the eyes were directed towards the observer. Our studies show that both head orientation and eye gaze influence the observer's orienting responses.