Abstract
The percept of the global form of a Glass pattern can be modulated by the presence of a surround Glass pattern (Li & Chen, 2010, JOV). This modulation depends on the global structures of both the central target and the surround. Here, we investigated whether such modulation can be influenced by the 3D configuration of the stimuli. The stimuli contained a central target (2.5deg radius) and an annulus surround (2.3 deg width). Both the target and surround were either concentric, radial or spiral Glass patterns (0.01 dot density). The depth modulation were achieved by binocular disparity. There were six 3D configurations: The target and surround were (A) on the same frontoparallel plane; (B) on different frontoparallel planes; (C) on the same 45 deg slanted plane; (D) on different slanted plane (+/-45 deg); (E) on the same concave or convex surface; and (F) one on a concave surface while the other on a convex surface. The coherence thresholds of the central target Glass patterns were measured at 75% accuracy with a 2AFC paradigm with or without the presence of a surround Glass pattern. When they are on the same surface, the concentric surround suppressed the detection of a concentric target, the spiral surround suppressed the detection of both concentric and radial target, and the radial surround suppressed the radial target detection regardless whether the surface was frontoparallel, slanted concave or convex. Such surround modulation effect was reduced or abolished when the target and the surround were on different surfaces. The surround modulation occurred only when the target and surround were either coplanar or on the same concave/convex surface regardless the depth difference between the target and the surround. Our results show that the surround modulation in Glass patterns depends on surface assignment.
Meeting abstract presented at VSS 2013