Kinematic specification of dynamics as an informational basis for person-and-action perception: Expectation, gender recognition, and deceptive intention.

The widespread conviction that perceiving another person must rest on ambiguous and fakeable information is challenged. Arguing from biomechanical necessities inherent in maintaining balance and coping with reactive impulses, we show that the detailed kinematic pattern is specific to an acting persons anatomical makeup and to the working of his or her motor control system. In this way information is potentially available about gender, identity, expectations, intentions, and what the person is in fact doing. We invoke the lawfulness of human movement, as elucidated by recent advances in motor control theory, to demonstrate the virtual impossibility of performing truly deceptive movements and to argue in general terms for the specification power inherent in human kinematics. The outcome of the analysis is subsumed under a principle of kinematic specification of dynamics (KSD), which states that movements specify the causal factors of events. Generally, a linked multiple degrees-of-freedom system does not exhibit substitutability; a change in one of its input factors cannot substitute for, or cancel, the multivariable effects of a change in another factor. Six explorative experiments are reported. Displaying humans in action with Johanssons