Categorizing sex and identity from the biological motion of faces

Abstract

Head and facial movements can provide valuable cues to identity in addition to their primary roles in communicating speech and expression [1-8]. Here we report experiments in which we have used recent motion capture and animation techniques to animate an average head [9]. These techniques have allowed the isolation of motion from other cues and have enabled us to separate rigid translations and rotations of the head from nonrigid facial motion. In particular, we tested whether human observers can judge sex and identity on the basis of this information. Results show that people can discriminate both between individuals and between males and females from motion-based information alone. Rigid head movements appear particularly useful for categorization on the basis of identity, while nonrigid motion is more useful for categorization on the basis of sex. Accuracy for both sex and identity judgements is reduced when faces are presented upside down, and this finding shows that performance is not based on low-level motion cues alone and suggests that the information is represented in an object-based motion-encoding system specialized for upright faces. Playing animations backward also reduced performance for sex judgements and emphasized the importance of direction specificity in admitting access to stored representations of characteristic male and female movements.

Categorizing identity from facial motion

“…Other studies of face learning and recognition from dynamic stimuli report parallel findings (e.g., Pilz, Thornton & Bülthoff, 2006;Hill & Johnston, 2001;Knight and Johnston, 1997). Similar results have also been documented in infant populations (e.g., Otsuka et al, 2009).…”

“…Inversion paradigms affect static face recognition by disrupting configural processing and early structural encoding of facial features (Valentine, 1988;Itier & Taylor, 2002). A similar effect has been found for moving faces, in which inversion impairs the ability to accurately discriminate gender and identity (Hill & Johnston, 2001). …”

“…The current study builds upon the work of Hill and Johnston (2001) who used animations derived from marker--based motion capture. Here, recent developments in marker--less technology were exploited to generate accurate and realistic models of facial movement.…”

Decoding Actions and Emotions in Deaf Children: Evidence From a Biological Motion Task

“…However the findings fail to support our hypothesis speculating that motion may significantly enhance emotion identification ability in the deaf (e.g. Hill & Johnston, 2001). Static representations (e.g.…”

Static and dynamic body image in bulimia nervosa: Mental representation of body dimensions and biological motion patterns

“…In fact, neurophysiological investigations of nonhuman primates as well as brain imaging work in humans have provided first hints that the brain is more responsive to conspecific action and movement patterns than it is to static images of a human figure. [18][19][20][21] The movement of a human body contains information about identity 22 as well as a variety of different attributes such as sex, [23][24][25] emotional states, 26,27 and body weight. [28][29][30] All of these attributes are socially relevant 31 and probably play an important role in body image formation.…”