Perception of direction of motion reflects the early integration of first and second-order stimulus spatial properties

Abstract

Second-order Type I and Type II plaids were constructed by combining two orientation-filtered random-dot gratings. Each component consisted of a dynamic filtered random-dot field, the contrast of which was modulated by a drifting sinusoidal grating. Orienting the two components suitably and interleaving at 120 Hz allowed us to produce a two-dimensional plaid pattern made from one-dimensional second-order components. The perceived direction of motion of both Type I and Type II plaids was measured as a function of the orientation content of the carrier, the contrast, and the duration of the stimulus. Type I plaids had a perceived direction close to the intersection of constraints/vector sum so..