Surface continuity and discontinuity bias the perception of stereoscopic depth

Abstract

Binocular disparity signals can provide high acuity information about the positions of points, surfaces, and objects in three-dimensional space. For some stimulus configurations, however, perceived depth is known to be affected by surface organization. Here we examine the effects of surface continuity and discontinuity on such surface organization biases. Participants were presented with a series of random dot surfaces, each with a cumulative Gaussian form in depth. Surfaces varied in the steepness of disparity gradients, via manipulation of the standard deviation of the Gaussian, and/or the presence of differing forms of surface discontinuity. By varying the relative disparity between surface edges, we measured the points of subjective equality, where surfaces of differing steepness and/or discontinuity were perceptually indistinguishable. We compare our results to a model that considers sensitivity to different frequencies of disparity modulation. Across a series of experiments, the observed patterns of change in points of subjective equality suggest that perceived depth is determined by the integration of measures of relative disparity, with a bias toward sharp changes in disparity. Such disparities increase perceived depth when they are in the same direction as the overall disparity. Conversely, perceived depth is reduced by the presence of sharp disparity changes that oppose the sign of the overall depth change.

Impairment of cyclopean surface processing by disparity-defined masking stimuli

“…In addition, later processing stages could add further noise or distortion to disparity measurement processes. These could involve both additional absolute disparity processes, such as disparity averaging (e.g., Cammack & Harris, 2016) or processing at the relative disparity level (e.g., Goutcher et al, 2018). Thus the apparent limiting effects of large cross-correlation windows may reflect the scale over which higher resolution absolute disparity measurements (i.e., those arising from smaller cross-correlation windows) are brought together to feed into subsequent mechanisms for the measurement of relative disparity.…”

“…Note that this potential spatial scale effect of relative disparity processing is distinct from the point-to-point measurements of relative disparity in the dipole model. Instead, such effects could reflect the smoothing of absolute disparities seen with the use of cyclopean frequency-tuned hypercyclopean filters (Goutcher et al, 2018;Hibbard, 2005;Serrano-Pedraza & Read, 2010;Tyler, 2012;Tyler & Kontsevich, 2001).…”

“…Tyler (1975Tyler ( , 2012 has suggested a progression from initial disparity measurement units to units with frequency-tuned selectivity for depth sinusoids. The tuning properties of these "hypercyclopean" channels have been used to account for orientation dependencies in sensitivity to cyclopean form (Hibbard, 2005;Serrano-Pedraza & Read, 2010;Tyler & Kontsevich, 2001) and structure-related biases in perceived depth (Goutcher et al, 2018). Such mechanisms would encode much of the information contained within the dipole distributions examined here, although also subject to those aspects of measurement noise on which antiphase masking effects appear to depend.…”

“…Beginning at V2, and continuing through multiple cortical sites, neurons show selectivity for relative disparities, that is, for differences between absolute disparity measurements across space (Fang et al, 2018;Neri, Bridge & Heeger, 2004;Thomas, Cumming & Parker, 2002;Umeda, Tanabe & Fujita, 2007). Although sensitivity for relative disparities has not been modeled extensively (cf., Assee & Qian 2007;Zhaoping, 2002), numerous psychophysical observations suggest the importance of processes operating at this level (e.g., Deas & Wilcox, 2014;Deas & Wilcox, 2015;Glennerster & McKee, 1999;Glennerster & McKee, 2004;Goutcher & Hibbard, 2010;Goutcher, Connolly & Hibbard, 2018;Goutcher & Wilcox, 2016;Vreven, McKee & Verghese, 2002;Wardle & Gillam 2016). Such results indicate that the tuning properties of relative disparity mechanisms are critically important for understanding the perception of cyclopean form (Goutcher et al, 2018;Hibbard, 2005;Tyler, 1975;Tyler, 2012;Tyler & Kontsevich, 2001).…”

“…Cyclopean perception (Julesz, 1971), our ability to perceive the 3D shape and structure of surfaces from binocular disparity alone, may, for example, be limited primarily by early absolute disparity measurement processes, as noted earlier. Alternatively, performance impairments may be more directly related to limitations in the measurement of relative disparities, or in the use of these measurements for the description of cyclopean form (e.g., Goutcher & Wilcox, 2016;Goutcher et al, 2018;Wardle & Gillam, 2016). In this article, we report the results of experiments measuring performance impairments for cyclopean surface perception in the presence of different forms of random-dot masking stimuli.…”