These findings suggest that chimpanzees also rapidly detect a face among non-face objects, as determined in humans by Hershler and Hochstein 12.

Furthermore, chimpanzees exhibit results similar to humans regarding spatial attention caused by facial stimuli 8. These findings suggest that chimpanzees perceive faces in a holistic manner, as do humans. In particular, there is accumulating evidence of various aspects of perception and cognition related to faces in chimpanzees: the face-inversion effect 16, 18, 21, 22, perception of facial expression 30, 31, hemispheric specialization of face processing 19, 21, perception of gaze perception 23, 32, 33, perception of a Mooney face 34, development of facial recognition 20, 35, and effects of long-term experience 5. initially proposed 9, but also by higher-order object categories such as faces 12, 13, although controversies remain 14, 15.įace perception in nonhuman primates has also been intensively studied from the cognitive-neuroscientific and comparative-cognitive perspectives 1, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29. They suggested that the pop-out effect or very efficient searching is caused not only by low-level “features”, as Treisman et al. Hershler and Hochstein clearly demonstrated this phenomenon using various stimuli and experimental conditions 12. In contrast, when a face appears among non-face objects (such as cars, houses, etc.), it is detected without any “effort”. When a search display contains only facial stimuli and observers are required to find a specific face among other faces, researchers often fail to find pop-out effects 11. Attention to a face can be examined in terms of the presence of “pop-out” or “efficient” searching when using a visual search paradigm 9, 10. For example, when a face is presented abruptly in peripheral vision, our visual attention shifts automatically 6, 7, 8. This type of processing is most evident for faces, although expertise (long-term intensive experience) on specific object categories also causes a shift in processing from featural to holistic processing 4, 5.įaces also capture our visual attention quickly. This result strongly suggests that humans process faces in a holistic manner. Furthermore, when a first-order spatial configuration among facial features (horizontally arranged eyes and nose and mouth located beneath the eyes) is distorted, face recognition is readily disturbed 3. For example, we are severely hampered 1, 2 when we see upside-down faces. Many studies have shown that faces are processed rather differently from other object categories. Faces convey various kinds of information that are critical for our social lives. The face is quite an important stimulus for humans. This conclusion was supported by a simple simulation experiment using the saliency model.

Efficient face detection was hampered by an inverted presentation, suggesting that configural processing of faces is a critical element of efficient face detection in both species. Chimpanzees also detected a photograph of a banana as efficiently as a face, but a further examination clearly indicated that the banana was detected mainly due to a low-level feature (i.e., color).

Additional testing showed that a front-view face was more readily detected than a profile, suggesting the important role of eye-to-eye contact. They also found human adult and baby faces-but not monkey faces-efficiently. This efficient search was not limited to own-species faces. We report that chimpanzees detected chimpanzee faces among non-facial objects quite efficiently. Furthermore, recent studies have shown that humans detect human faces among non-facial objects rapidly. Both species exhibit the face-inversion effect in which the inverted presentation of a face deteriorates their perception and recognition. Recent advances in comparative-cognitive research clearly indicate that chimpanzees and humans process faces in a special manner that is, using holistic or configural processing. The face is quite an important stimulus category for human and nonhuman primates in their social lives.

Chimpanzee face front view