Visual perception of faces and bodies beyond identity: Role of gaze direction and emotion

Research on face perception is abundant. Over 200 studies were published by the time that the first face perception models were conceptualized in the eighties. At present, researchers generally agree that identity-information in the face is extracted by means of holistic mechanisms, enabling human observers to perceive and integrate featural and relational information in the face in a single glance. This has encouraged many researchers in the field to conclude that we are experts at face recognition. Complementary to this statement is the finding that some people lack this so-called expertise, and moreover, experience a marked difficulty to recognize people from their face. This condition, termed prosopagnosia, further emphasizes the astonishing ability of human observers to recognize faces, and the impact of a loss thereof.

            Despite what is now known about identity perception, and holistic identity perception in particular, research on other facial aspects, such as emotion and gaze, has been lagging behind. Gaze perception has been investigated extensively in the context of social psychology, but is far less studied in the domain of face perception. Moreover, the fact that studies assessing identity, emotion, and gaze are often segregated is quite surprising, given the fact that these sources of information originate from the same stimulus (i.e., the face), and are often (if not always) simultaneously present. A similar remark could be made in regard to face perception in a population with prosopagnosia. The fact that emotion and gaze perception remain relatively unstudied in this population is not completely surprising however, as abnormal identity perception is the primary symptom in prosopagnosia. Nonetheless, findings on holistic identity perception in prosopagnosia are inconsistent, and studies on emotion and gaze perception could help form a theoretical framework on prosopagnosia, and are even necessary to take into account considering the above mentioned fact that identity, emotion, and gaze are rarely perceived as separate dimensions in real life. Finally, studies on holistic body perception have only recently emerged, but this topic deserves more attention considering the resemblance in functionality (i.e., communication) and configuration between faces and bodies.

            During the course of this PhD, we thus aimed to investigate not only holistic identity perception, but also gaze and emotion perception, and the interaction between these dimensions. In Study 1, a well-known design to study holistic identity integration (i.e., the composite design) was adapted for our aim to assess holistic gaze integration, in faces and bodies. This design was then implemented on a population with congenital prosopagnosia (CP), the prosopagnosia subtype believed to be present from birth (Study 2). In Study 3 and 4, the integration between identity and gaze, and identity and emotion was investigated using the composite design (Study 3), and the redundancy gain paradigm (Study 4).

            To summarize, unlike what is generally believed for identity perception, Study 1 and 2 revealed that people with CP seemed to integrate gaze cues in faces and bodies stronger compared to normal controls. The integration of identity and gaze, and identity and emotion was not confirmed in Study 3 and 4, and as such, methodological factors from these studies were further investigated.