Abstract
[Purpose] To reveal the mechanism of perceptual filling-in, the author examined the time for filling-in when two targets were presented on a background. The previous study showed that filling-in at two separated targets could interact with each other in the case that targets and background differed in luminance (ARVO-2000, #2340). The present study asked characteristics of the interaction when they differed in orientation. [Method] Participants observed a color monitor binocularly from 50 cm distance with their head fixed by a chin rest. They should fixate at the center cross throughout a trial. Two Gabor patches were presented on a uniform sinusoidal grating. The position and orientation of one patch (‘test target’) were fixed whereas those of the other patch (‘interference target’) were manipulated as experimental conditions. Participants were asked to respond immediately after the test target faded away. The author examined how the reaction times (RTs) varied dependent on the properties of the interference target. [Result] First, RTs were significantly modulated by the orientation of the interference target. Second, the effect of the interference target was reduced as the targets were more separated. Third, the effect depended also on the background orientation: More remarkable modulation was observed when the test target and background had similar orientations than when they had different orientations. [Conclusion] Inter-target interaction of perceptual filling-in was observed in the orientation domain. The result seems related to the neurophysiological findings on contextual modulation in visual cortex and suggests that the balance of competitive neural activities, rather than the edge adaptation, is a more important factor determining the time for filling-in.
Supported by CREST, JST, Japan.