STIMULUS-ONSET ASYNCHRONY IS NOT NECESSARY FOR MOTION PERCEPTION OR METACONTRAST MASKING

Coherent directional motion is seen if a translated image is displayed in two sequential frames (F1 and F2). In a related paradigm-metacontrast masking-the mask (F2) reduces the visibility of the target (F1). Although strict temporal succession has been considered essential in both paradigms, we obtained both coherent motion and metacontrast masking with simultaneous onsets of F1 and F2, provided that F2 outlasted F1. Computational models of motion sensors are inherently capable of explaining these results, but inhibitory theories of metacontrast masking are disconfirmed.