Conspecific and human face processing in monkeys (Macaca mulatta): An eye movement investigation

The perceived salience of faces and facial features can be modulated by manipulations like inversion (change in global configuration) or blurring (reduction of feature-based information). By applying these manipulations to images of monkey and human faces, we examined the processes underlying face perception in monkeys. Eye movements were investigated during a non-reinforced passive-viewing task. The faces were either familiar or unfamiliar. We found that eye-movement patterns did not differ across familiarity, but differed across species. Conspecific faces elicited higher proportions of fixation and viewing time for eyes than any other facial feature in the upright and blurred conditions, but not in the inverted condition. In contrast, for human faces we did not find a systematic difference for both measures across facial features. These results show that conspecific faces--unlike human faces--are processed holistically as eyes attract the monkeys‘ gaze only in an upright context--a clea r indication of a high-level influence on eye movements due to face processing