Biological Motion

Johansson (1973) attached small points of light at the joints of human actors, and filmed them moving about in the dark. Observers viewing the film reported vivid impressions of human figures, even though the images contained a few isolated bright points. This demonstration of the effect was created using a computer rather than real actors, but the result is similar. Research has also shown that we can even judge the gender of the walker reliably from these displays (see Mather & Murdoch, 1994 ). Evidently, motion is sufficient to extract meaningful interpretations of articulated 3-D forms as well as of rigid 3-D forms. The visual system must integrate relatively low-level information about the movements of individual dots over large areas of the image to deduce the pattern of connectivity between dots (eg. ankle dot joined to knee dot, not to the other ankle dot). Try pausing the movie - is the figure still visible?