3D Surface configuration effect in Glass Pattern perception P-Y Chen, C-C Chen |
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Department of Psychology, National Taiwan University, Taiwan
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| We investigated how 3D surface configuration affects 2D Glass pattern perception. Glass patterns consist of randomly distributed dot pairs, or dipoles, whose orientations follow a geometric transform. The stimuli were concentric Glass patterns (2.5deg radius) consisted of dots (2.3’ x 2.3’) with 4% density. The 3D surface modulations were achieved by manipulating binocular disparity of dots. There were two 3D configurations: slanted (the first order), where the depth changed linearly from one side to the other, and concave/convex (the second order), where the depth changed with a projectile centered at the fixation. We measured the coherence threshold for detecting the Glass patterns on these surfaces at 75% accuracy with a 2AFC paradigm. In the first order conditions, the coherence threshold was always the same as that measured on the frontoparallel plane regardless the slant of the surface. In the second order conditions, however, the threshold increased with surface curvature linearly on log-log coordinates. Our result suggests that the Glass pattern detection is viewpoint invariant and thus may have an underlying 3D representation. In addition, such 3D representation is the first order rather than the second order surfaces. |
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