The visual perception of dynamic body language

Traditional models describe the visual system as a general-purpose processor that analyzes all categories of visual images in the same manner. For example, David Marr (1982) in his classic text Vision described a single, hierarchical system that relies solely on visual processes to produce descriptions of the outside world from retina images. Similarly, Roger N Shepard (1984) understood the visual perception of motion as dependent upon the same processes no matter what the image. As he eloquently proposed, " There evidently is little or no effect of the particular object presented. The motion we involuntarily experience when a picture of an object is presented first in one place and then in another, whether the picture is of a leaf or of a cat, is neither a fluttering drift nor a pounce, it is, in both cases, the same simplest rigid displacement " (p. 426). This traditional approach presents a fruitful counterpoint to functionally inspired models of the visual system. Leslie Brothers (1997), one of the pioneers of the rapidly expanding field of Social Neuroscience, argued that the brain is primarily a social organ. As such, she posited that neurophysiologists could not understand how the brain functions until they took into consideration the social constraints on neural development and evolution. According to this view, neural structures are optimized for execution and comprehension of social behavior. This raises the question of whether sensory systems process social and non-social information in the same way. Extensive research has addressed the communication of social information by facial and hand gestures (e.g. Streeck 2002; Haxby and Gobbini 2007). The goal of this chapter is to address another conveyer of social information; that is, the actions of the human body. In the popular press, numerous books have purportedly identified the precise information communicated by various body postures. For example, in The Definitive Book on Body Language (Pease and Pease 2006), the authors claim to have discovered the body postures that communicate lying, bluffing, and sexual interest. While enticing, the conclusions reported in the popular press are generally not grounded in methodologi-cally rigorous experiments. Nonetheless, the research described below is in agreement with the popular press's take on the perception of " body language " on one fundamental point; namely, that the human body communicates extensive social information. The goal of this chapter is to provide a state-of-the-art review of psychophysical and neuro-physiological findings regarding the perception of …