Perceptual biases and cue weighting in perception of 3D slant from texture and stereo information

Abstract

Multiple cues are typically available for perceiving the 3D slant of surfaces, and slant perception has been used as a test case for investigating cue integration. Previous evidence suggests that texture and stereo slant cues contribute in an optimal Bayesian manner. We tested whether a Bayesian model could also account for perceptual underestimation of slant from texture. One explanation proposed by Todd, Christensen, and Guckes (2010) is that slant from texture is based on an inaccurate optical variable. An alternative Bayesian explanation is that perceptual underestimation is due to the influence of frontal cues and/or a frontal prior, which is weighted according to the reliability of slant cues. We measured slant perception using a hand-alignment task for conditions that provided only texture, only stereo, or combined texture and stereo cues. Slant estimates from monocular texture showed large biases toward frontal, with proportionally more underestimation at low slants than high slants. Slant estimates from stereo alone were more accurate, and adding texture information did not reduce accuracy. These results are consistent with a frontal influence that is decreasingly weighted as slant information becomes more reliable. We also included conditions with small cue conflicts to measure the relative weighting of texture and stereo cues. Consistent with previous studies, texture had a significant effect on slant estimates in binocular conditions, and the relative weighting of texture increased with slant. In some cases, perceived slant from combined stereo and texture cues was higher than from either cue in isolation. Both the perceptual biases and the cue weights were generally consistent with a Bayesian model that optimally integrates texture and stereo slant cues with frontal cues and/or a frontal prior.

Perception of 3D slant from textures with and without aligned spectral components

“…Previous studies have found that slant from texture is underestimated with monocular viewing (Saunders, 2003;Todd et al, 2005;Watt et al, 2005;Norman et al, 2009;Durgin, Li & Hajnal, 2010;Saunders & Chen, 2015), and the underestimation is greater when texture information is degraded (Saunders, 2003;Rosas et al, 2004;Todd et al, 2005;Saunders & Chen, 2015). One possible explanation is that texture information is integrated with prior knowledge or frontal cues (e.g., accommodation), resulting in biases toward frontal when texture information is unreliable (Saunders & Chen, 2015).…”

“…These plaid textures provide texture compression and scaling cues with or without the aligned spectral components, so any observed differences could be attributed to the orientation information provided by these components. Observers viewed planar surface patches with different slants and performed a manual slant estimation task (Saunders & Chen, 2015). In Experiment 1, we used a medium size FOV (168), and in Experiment 2 we used a smaller FOV (68) that is closer to the size of the stimuli used by Tam et al (2013).…”

“…If perceptual underestimation is not due to a frontal prior or frontal cues, a difference in perceptual bias might still be expected. A number of studies have found that degrading texture information or reducing texture cues leads to greater underestimation of slant (Saunders, 2003;Rosas et al, 2004;Todd et al, 2005;Saunders & Chen, 2015). To the extent that the visual system relies on perspective convergence of oriented spectral components to perceive slant from texture, removing the aligned components would be expected to increase perceptual biases toward frontal.…”

“…Cue conflict stimuli were constructed as previous studies (Knill & Saunders, 2003;Hillis et al, 2004;Saunders & Chen, 2015). The images simulated the result of first computing a cyclopean projected image of a textured surface viewed from the desired slant from texture, then back-projecting the cyclopean image onto a 3D surface with the desired slant from stereo, and then computing stereo perspective views of 3D surface with back-projected texture.…”

“…When a textured surface is viewed in perspective, deformations of the texture in the projected image provide information about the 3D structure of the surface. Previous studies have shown the visual system can utilize texture information from a monocular image to perceive the 3D slant of planar surfaces (e.g., Rosenholtz & Malik, 1997;Knill, 1998a;Tibau, Willems, van den Bergh, & Wagemans, 2001;Saunders, 2003;Rosas, Wichmann, & Wagemans, 2004;Norman, Crabtree, Bartholomew, & Ferrell, 2009;Todd, Christensen, & Guckes, 2010;Saunders & Chen, 2015), and to perceive the 3D shape of curved surfaces (e.g., Todd & Akerstrom, 1987;Li & Zaidi, 2000;Todd, Thaler, & Dijkstra, 2005;Todd, Thaler, Dijkstra, Koenderink, & Kappers, 2007;Todd & Thaler, 2010). Texture information also contributes to 3D perception in binocular viewing conditions that provide stereo depth information, as demonstrated by studies using a cue conflict paradigm (Gillam, 1968;Buckley & Frisby, 1993;Knill & Saunders, 2003;Hillis, Watt, Landy, & Banks, 2004;Watt, Akeley, Ernst, & Banks, 2005;Rosas, Wagemans, Ernst, & Wichmann, 2005;Girshick & Banks, 2009;Saunders & Chen, 2015).…”