Illusory occlusion affects stereoscopic depth perception

Zhimin Chen,David Whitney,Gerrit W Maus,Rachel N Denison

doi:10.1038/s41598-018-23548-3

Zhimin Chen, David Whitney + Show 2 more

Open Access

https://doi.org/10.1038/s41598-018-23548-3

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Abstract

When occlusion and binocular disparity cues conflict, what visual features determine how they combine? Sensory cues, such as T-junctions, have been suggested to be necessary for occlusion to influence stereoscopic depth perception. Here we show that illusory occlusion, with no retinal sensory cues, interacts with binocular disparity when perceiving depth. We generated illusory occlusion using stimuli filled in across the retinal blind spot. Observers viewed two bars forming a cross with the intersection positioned within the blind spot. One of the bars was presented binocularly with a disparity signal; the other was presented monocularly, extending through the blind spot, with no defined disparity. When the monocular bar was perceived as filled in through the blind spot, it was perceived as occluding the binocular bar, generating illusory occlusion. We found that this illusory occlusion influenced perceived stereoscopic depth: depth estimates were biased to be closer or farther, depending on whether a bar was perceived as in front of or behind the other bar, respectively. Therefore, the perceived relative depth position, based on filling-in cues, set boundaries for interpreting metric stereoscopic depth cues. This suggests that filling-in can produce opaque surface representations that can trump other depth cues such as disparity.

Highlights

When occlusion and binocular disparity cues conflict, what visual features determine how they combine? Sensory cues, such as T-junctions, have been suggested to be necessary for occlusion to influence stereoscopic depth perception
In Experiment 2B (Fig. 6), when the monocular bar was presented alone, observers perceived its depth to be equivalent to a binocular bar with crossed disparity (PSE = −0.36°, SEM = 0.074°), which is significantly closer in depth than an object of zero disparity (t(5) = −4.9, p = 0.0045, Cohen’s d = −2.8)
When the binocular bar appeared later and was more likely to be seen as occluding the monocular bar, observers perceived it at a points of subjective equality (PSE) disparity of −0.53° (SEM = 0.070°) and as significantly closer in depth than when the monocular bar appeared later, t(5) = −2.7, p = 0.042, Cohen’s d = −1.7, not significantly closer than its baseline perceived depth (t(5) = −1.3, p = 0.26, Cohen’s d = −0.80)

Summary

Introduction

When occlusion and binocular disparity cues conflict, what visual features determine how they combine? Sensory cues, such as T-junctions, have been suggested to be necessary for occlusion to influence stereoscopic depth perception. Occlusion and disparity are two prevalent ordinal and metric cues, respectively, and they have been pitted against each other in the laboratory for studying cue combination Occlusion cues, such as T-junctions, L-junctions and bounding contours, can convey unambiguous relative position information about the two objects, so that when occlusion and stereoscopic cues conflict and give incompatible depth information, occlusion usually overrides disparity. Rather than fusion or the appearance of transparency, either bar was found to be perceptually filled in and seen in front of the other This ambiguous global depth configuration is resolved by a rivalry process, which leads to perception of an unambiguous interpretation of one bar being occluded by the other, and over time the perceived depth ordering alternates[21]

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Results

Conclusion