Prior knowledge does not facilitate the perceptual organization of dynamic random-dot patterns

Three classes of models for the origins of perceptual organization—linear independence, cognitive facilitation, and self-organization—were tested by evaluating the effects of stimulus unccrtainty and pattern coherence on the detection of coherent motion in dynamic random-dot patterns. Stimulus patterns consisted of two successive frames of randomly positioned dots in which motion was perceived when the dot positions in successive frames were correlated and displaced. The number of alternative directions axed locations of motion and the degree of coherences correlation) between the two successive frames were manipulated. The effects of stimulus uncertainty were less than predicted by cognitive facilitation models and were less than predicted by one linear independence model Ichoice theory), although similar to the predictions of another linear model (the Peterson, Birdsall, & Fox, 1954, approximation of the optimum Gaussian model). Small, but significant, tendencies toward self-organization rather than linear independence of perceived motion in neighboring locations were indicated by a nonlinear effect of coherence on detection accuracy and by the superior detectability of the direction as compared with the location of motion.