The line motion illusion: the detection of counterchanging edge and surface contrast.

A version of the line motion illusion (LMI) occurs when one of two adjacent surfaces changes in luminance; a new surface is perceived sliding in front of the initially presented surface. Previous research has implicated high-level mechanisms that can create or modulate LMI motion via feedback to lower-level motion detectors. It is shown here that there also is a non-motion-energy, feedforward basis for LMI motion entailing the detection of counterchange, a spatial pattern of motion-specifying stimulus information that combines changes in edge contrast with oppositely signed changes in background-relative surface contrast. It was concluded that (1) in addition to LMI motion, edge/surface counterchange could be the basis for perceiving continuous object motion, (2) counterchange detection is the likely basis for third-order motion perception (Lu & Sperling, 1995a), and (3) motion energy and counterchange mechanisms could be composed of different arrangements of the same spatial and temporal filters, the former detecting motion at a single location, the latter detecting the motion path between pairs of locations.