Abstract
Li, Brenner, Cornelissen and Kim (2002) have recently reported that the perceived shape of spatiotemporally defined 2D object was systematically distorted during pursuit eye movement and that the perceived shape just reflected the retinal image. Does this imply that the perceptual shape distortion during pursuit eye movement is determined in the early level of visual information processing? Although the perceived shape just reflected the retinal image ignoring extra retinal information, it is still possible that the perceived shape is determined at a late stage, e.g., later than binocular information is processed. To examine this possibility, I measured the effect of reference on the perceptual shape distortion during pursuit eye movement in three separate conditions; no-reference, dichoptic (i.e., target and reference were presented to separate eyes), and binocular conditions. If perceptual shape distortion is determined before binocular information is processed, then perceptual distortion should not be affected by the dichoptically presented reference. The size of the spatiotemporally defined object was 1.6 deg × 1.6 deg. The luminance-defined rectangular reference surrounding the target object had one of three sizes; 2.1 deg × 2.1 deg, 2.6 deg × 2.6 deg, and 3.1 deg × 3.1 deg. Subjects reported the perceived shape by the method of adjustment. As found in Li et al, the perceived shape of the target object was systematically distorted during pursuit eye movement, but the amount of perceptual distortion decreased as the reference became closer to the target. More interestingly, the dichoptically presented reference affected the perceptual shape distortion as the binocularly presented reference did. No significant difference in the amount of perceptual distortion was found between these two conditions. These results imply that the perceptual shape distortion observed by Li et al is determined later than binocular information is processed.
Supported by M103KV010021-04K2201-02140 from BRC, 21st Century Frontier Research Program