Surround Modulation of Global Form Perception
Date Issued
2010
Date
2010
Author(s)
Li, Hsin-Hung
Abstract
We demonstrate a novel surround modulation of global form perception by using Glass patterns in a center-surround configuration. Glass patterns contain randomly distributed dot pairs, or dipoles, whose orientations are determined by a geometric transform. By integrating across dipoles, an observer can perceive a specific global structure in the image. We measured the coherence threshold, the minimum proportion of signal dots needed in the target for an observer to detect the global form, at 75% accuracy with a 2AFC paradigm. The coherence thresholds of the central target Glass patterns were either measured alone or measured with the presence of various Glass pattern surrounds. Concentric and spiral surrounds increased the coherence threshold for the concentric target compared with that measured for the target alone, while a radial surround had no effect. The coherence threshold for the radial pattern, however, was elevated only by the spiral surround while the spiral and translational Glass patterns were not affected by any surrounds. The effect persisted when the center and the surround were segregated by a blank gap, and the amplitude of the modulation peaked at an optimal distance between the center and the surround. Our results show that global form perception can be modulated by a surround, and this modulation depends on the shapes of the central target and the surround context.
Subjects
lateral interactions
pattern discrimination
Type
thesis
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