Presentation Information
[P2-13]Temporal unfolding contributes to interocular comparison for motion-in-depth perception in peripheral vision
*Ikuya Murakami1 (1. The University of Tokyo (Japan))
Keywords:
Motion in depth
Time has often been considered as a confounder in stereoscopic depth perception. For example, the Pulfrich effect tells us that when one eye somehow requires longer latency, the visual system is ignorant of the actual cause of lags and ascribe them to spatial lags between eyes, hence fake binocular horizontal disparities producing illusory depths. However, recent studies have suggested that dynamic depth cues may help construct motion-in-depth perception. Due to their subtle efficacy and other geometrical constraints, most studies have been conducted around the fovea, and little is known about the characteristics in the periphery, where changing disparity over time (CDOT) may help construct dynamic scenes, but effects of another dynamic depth cue, interocular velocity difference (IOVD), are unknown. We aimed to examine whether motion-in-depth perception in peripheral vision is possible solely from the IOVD when fine grating patterns move oppositely between eyes. Gratings were chosen because they were compatible with a unitary grating object moving in depth in a real scene. Importantly, the spatial frequency of the gratings was set sufficiently high to maintain the maximally attainable disparity still below depth detection threshold at the tested eccentricity, making the CDOT useless. These gratings moved either leftward or rightward at a constant speed, forming four conditions that were consistent with four different motion percepts: receding, approaching, leftward, and rightward. Observers were asked to indicate perceived motion by three alternative forced response: receding, traversing, and approaching. If the grating in one eye tended to mask the grating in the other eye, the traversing responses would be a great majority irrespective of the conditions. Contrary to this prediction, the results indicated that observers well discriminated the conditions of non-zero IOVDs from the conditions of traversing, suggesting interocular comparison. Even though none of the component frames produce depth, their animation over time does.