Motion Capture Illusion


Nowadays the term 'motion capture' is used to describe the process of recording the 3-D movements of objects or actors in order to reproduce them in computer games and movies. But in the 1980's it was used to describe an illusion in which random movements of small dots were 'captured' by the coherent movement of larger shapes in the display.
In this animated display a grating jumps back and forth between two positions separated by a quarter of its spatial period. In each animation frame a different field of random black dots is superimposed on the grating. Although the two sets of dots are completely uncorrelated, their movement is 'captured' by the apparent motion of the grating, so they appear to move along with it. The capture is probably caused by cooperative interactions between neurons coding the movements of the grating and dots. The lateral motion signals from the grating may serve to boost random side-to-side signals from the dots at the expense of all the other directions available from random dot pairings, so the dots appear to move with the grating.
Ramachandran, V., and Cavanagh, P. (1987) Motion capture anisotropy. Vision Research, 27, 97-106.