In Brief

People more adeptly recognize their own movements than those of their friends, but they still can distinguish friends' movements from those of strangers at better-than-chance rates, according to research in the February issue of the Journal of Experimental Psychology: Human Perception and Performance (Vol. 31, No. 1).

In the study, Rutgers University psychologist Maggie Shiffrar, PhD, and her colleagues recorded the movements of participants and their friends in activities such as walking, jumping, dancing and playing Ping-Pong, and deconstructed them into brief point-light movies. To create those movies, participants wore black clothes and 13 reflective white markers on their joints and heads while performing the movements on a black stage. A camera recorded the movement of the markers without any other personal identifiers like body shape.

Three months later, the participants viewed movies of their own movements, a friend's movements and those of a stranger and tried to classify the actors as themselves, friends or strangers.

The participants correctly identified movies of themselves 69 percent of the time, movies of their friend 47 percent of the time and movies of the stranger 38 percent of the time--just above chance.

The participants' strong ability to recognize their own movements suggests that the brain's system for moving the body contributes to its visual analysis of human movement that allows us to recognize individuals, says postdoctoral researcher Fani Loula, PhD, who worked on the study. However, the participants' above-chance recognition of their friend's movements suggests that visual experiences of human movement also contribute to recognition, she adds.

"The finding adds to our knowledge of body language and the strong interpretations people have of others' body language," Loula says. "It shows that we do relate our physical experiences to what we see other people do, which may be a critical point in analyzing behavior."

Also of interest, participants were best able to identify actors when their movements were unusual, such as in dancing or boxing; more common movements like walking or running were more difficult to identify, Loula says. That finding indicates relatively little information about identity--at least the kind decipherable by the human visual system--is available in a person's gait, the researchers say. Biometric scientists working to develop ways to identify individuals through their movements might focus their work on unusual movements, instead of gait, to take advantage of that finding, Loula says.