Abstract
The visual hemifields contain processing resources that are substantially independent across a handful of tasks, such as object tracking and extraction of visual statistics. We add a new task to this category - the ability to control ambiguous apparent motion. Participants viewed two simultaneous and identical dot quartet animations (300ms/frame) where each could be perceived as undergoing either vertical or horizontal motion. The default percept of such dual animations is to see both quartets move in the same manner, and careful mental control is needed to perceive them as moving differently. Each trial began with a cue for mental control: see this quartet moving vertically, and that quartet moving horizontally. The dependent measure was the amount of proximity-based 'help' (making dots closer either vertically or horizontally) that a participant needed to add using the method of adjustment, before they were confident that they could robustly perceive the cued motion pattern differently across the two quartets. This threshold level of needed help was lower when the quartets straddled the hemifield boundary in the lower visual field (mean aspect ratio of 1:1.2), compared to when the quartets were contained entirely within the left or right quadrant of the lower visual field (mean aspect ratio of 1:1.3), p< 0.05 with eccentricity controlled between conditions. We speculate that the separate resources that underlie this benefit for apparent motion share roots with the resources that bring hemifield benefits for object tracking tasks - more efficient deployment of multiple attentional 'spotlights' across the hemifield boundary.
Meeting abstract presented at VSS 2015