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?