MOTION CAPTURE OF LUMINANCE STIMULI BY EQUILUMINOUS COLOR GRATINGS AND BY ATTENTIVE TRACKING

Two experiments demonstrated motion capture of luminance-defined dots by gratings with no net luminance-based motion. In a series of two-fra me experimental trials, we superimposed bright dots and a color gratin g rotating in opposite directions. Capture was observed at equiluminan ce and was facilitated by the presence of color in gratings over a ran ge of luminance contrasts. In a second experiment, observers noted tha t when a counterphase grating was tracked in either direction with att ention, the superimposed dots were captured in that direction. These r esults suggest motion capture is supported not only by luminance-based motion, but also by color- and attention-based motion. Indeed, we sug gest that the most parsimonious explanation is that all capture is med iated by attention.