Retrieving Information from Human Movement Patterns

Biological motion—that is, the movement patterns of animals and humans—provides a rich source of information that helps us to quickly and reliably detect the presence of another living being; to identify it as a predator, prey, or conspecific; and to infer its actions and intentions in order to respond with adequate behavior. Once we know that we are being confronted with another person, we are able to use motion as a source of information about identity, gender, age, emotional state, and personality traits and as a complex means for signaling and communications. More than 30 years ago, the Swedish psychologist Gunnar Johans-son (1973) introduced a stimulus into experimental psychology that allows us to disentangle to a large degree the information contained in the kinematics of a moving body from other sources of information about action and identity. His work showed that a few light dots placed strategically on a moving human or animal body are instantaneously organized into the coherent percept of a living creature (also see Chapter 11 in this volume). The observation goes back to the earlier work of the pioneers of cinematography (Muybridge, 1887/1979) and bio-mechanics (Marey, 1895/1972), but it was Johansson (1973) who first