Studies of some new phenomena of motion perception.

Contrast modulation of a set of features in a Glass pattern invokes, under certain circumstances, the perception of motion in the absence of any physical displacements. The illusion is spatially limited to within about 10' and is governed by contrast relationships. We find that the detected motion in these situations is due to local computations the results of which can be integrated over retinal areas of more than 1 degree. The possible motion detection mechanisms are discussed within the framework of the Reichardt/Hassenstein and Marr/Ullman type of motion detectors.