Monkeys and mug shots: cues used by rhesus monkeys (Macaca mulatta) to recognize a human face

We investigated the cues rhesus monkeys (Macaca mulatta) use to recognize a familiar human face. To manipulate facial cues, schematic faces were constructed with Identi-Kit materials derived from mug shots. The monkeys (N = 4) spontaneously classed Identi-Kit as faces on initial presentations. The monkeys then learned to distinguish one Identi-Kit face, the standard, from others. Panel presses indicated recognition of the standard face. Eye movement recordings revealed that the monkeys predominantly fixated on the eyes of the standard face. When the standard face was transformed by removing, altering, or reorienting its features, only alterations of eyes or brows lowered recognition; removal of eyes, brows, nose, or lips did not. Responses to rotated, inverted, and scrambled versions of the standard face varied but generally disrupted recognition. We concluded that features and configuration were used to recognize the human face.