Both Perception and Action Are Biased by Local Motion When Reporting the Location of a Moving Target

摘要

When seen in the periphery, the perceived trajectory of a moving target is altered by the presence of local motion within the target (Tse & De Valois, 2006). In spite of this dramatic perceptual effect, there is evidence that targeting movements of the eye and hand are either less affected by the illusion (Lisi & Cavanagh, VSS 2014, 2015), or altogether unaffected (Lisi & Cavanagh, Current Biology 2015). However, it remains unclear whether this apparent dissociation reflects fundamental differences in the processing of visual motion for perception and action, or rather differences in the task requirements, since the perceptual tasks required the observer to report on the target's trajectory (or the allocentric relationship between the motion path's start and end), while the action tasks involved movements guided to the target's egocentric location. In two experiments, we assessed the accuracy of the perceptual and action systems in indicating the location of the start and end of a target's motion path. In Experiment 1, participants were asked to indicate these locations with either a saccadic eye movement, or by using a mouse to move a cursor. In both conditions, responses were significantly affected by the illusion, with reports of the end location biased in the same direction as the local motion, while reports of the starting location were biased in the opposite direction. In Experiment 2, subjects were asked to perceptually compare the location of the start or end of the motion path with a flash that preceded or followed the motion, respectively. As in Experiment 1, the perceived end of the motion path was biased in the same direction as the local motion, while the perceived start was biased in the opposite direction. These findings indicate that both perception and actions are fooled by the illusion when indicating the target's location.