Dynamic Aspects of Face Processing in Humans

The human face is capable of a wide variety of facial expressions that manifest themselves as usually highly non-rigid deformations of the face. On the one hand, this presents the visual system with a problem: Recognizing someone requires determining what information in the face remains constant despite the various facial deformations. Extraction of such invariant features will allow me, for example, to identify my neighbor regardless of whether he or she is smiling or looking sad. On the other hand, the impressive repertoire of changes can also be seen as a positive: It provides considerable information. The particular way my neighbor smiles or looks sad might well be used for identification, similar to how Jack Nicholson’s and Tom Cruise’s smiles are very specific to them. In addition to potentially providing information about who someone is, facial deformations can help us to infer something about a person’s age, social status, general health, level of fatigue, and focus of attention. Likewise, changes in the facial surface play a central, albeit often ignored, role in communication. Facial deformations that serve this latter role are generally referred to as facial expressions. A distinction should be drawn between the information that is present in a specific image and the information that must be present for that expression or person to be