Context improves motion speed estimation

Abstract

Velocity is always defined in relation to a frame of reference. The visual system shifts the reference frame from which it processes motion signals according to situation and context, e.g. the duncker illusion. We hypothesize that the visual system not only employs contextual stimuli to establish novel reference frames, but are also necessary to improve velocity calculation, i.e. velocity precision is impoverished when motion signals must be computed under isolated environments, even when the reference system remains known. To test this hypothesis we conducted speed discrimination tests under landmarked and isolated situations. Results show a significant increase in the webber fractions when stimuli were displayed in isolation. These results would indicate that contextual information may not only help establish novel coordinates systems when needed, but would as well help refine motion estimations under 'normal' (i.e. retinotopic) coordinate systems.