Abstract
Bias in perceived grouping was examined in conditions where the two eyes receive different spatial external distortion. Stimuli, 10x10 dots matrix with Horizontal and Vertical spacing defining the direction of grouping (V/H), were presented, in random order either to both eyes (B), or only to one (M) while the other exposed to background luminance. Cylindrical lens were used to introduce a constant distortion along one direction. Bias and reaction times (RT) were measured under three Dichoptic conditions: (1) Binocular and Monocular without distortion (2) orthogonal distortions between the eyes presented simultaneously or in different trials, (3) as in (2) but with M distortion to one eye. Task was to distinguish between H/V groupings without feedback. (1) a) without induced distortion subjects show no bias, with sharp transitions between V/H groupings, b) at the transition, RT increased, with B being slower than M by 108ms (2) orthogonal distortions between the eyes showed no B bias but large M bias (3) M distortions showed a bias in the treated eyes while untreated eyes showed orthogonal bias. B-RT was slower than the M-RT by 116ms. The bias with the dichoptic presentation was found to be the average of the two opposite M groupings. The finding that the RT of the B level is slower (∼100ms), and that M distortions bias the response of the untreated eye, suggest the existence of mutual interactions between the B and M processes.
Supported by the Israel Science Foundation (UP)