Abstract
To perceive the 3D layout of a scene, the visual system must parse the image into different objects (segmentation) and determine their relative distances (depth ordering). Either stereopsis or relative image motion resulting from movement of the observer (motion parallax) could serve as perceptual cues for these tasks, but very little is known about the effects of image statistics in either of these modalities. Here we examine the influence of specific higher-order texture statistics on depth and segmentation, in motion parallax and stereopsis, using naturalistic synthetic micropattern textures. The textures consisted of edgelet micropatterns at different densities, which could be phase-scrambled either locally or globally (Zavitz & Baker, 2013), thus allowing us to manipulate sparseness, global phase structure, and local phase alignments. The textures were displayed in a circular aperture (28 deg diameter). For motion parallax, relative texture motion (shearing) was synchronized to horizontal head movement with low spatial frequency (0.05 cpd) horizontal square wave modulations. Four observers performed a 2AFC depth ordering task, in which they reported which modulation half-cycle of the texture appeared in front of the other. Binocular vision was assessed by a similar depth ordering task of disparity-defined surfaces, with the same display and matched stimulus parameter settings. The observers also carried out a segmentation task in which they discriminated the orientation of a square wave modulated boundary in depth, in motion parallax or stereopsis. Surprisingly, we obtained a strikingly similar pattern of results for depth ordering and segmentation, and both motion parallax and stereopsis: (1) randomizing all structure by globally phase-scrambling the texture improved performance, (2) decreasing sparseness also improved performance and (3) removing local phase alignments had little or no effect. These results provide evidence for a commonality of early texture processing mechanisms for depth and segmentation in both motion parallax and stereopsis.
Meeting abstract presented at VSS 2016