The Venetian blind effect, binocular luster, and binocular rivalry

When one views a square-wave grating and changes the average luminance or contrast of the monocular images relative to each other, at least three perceptual phenomena occur. These are the Venetian blind effect, or a perceived rotation of the bars around individual vertical axes; binocular luster, or a perceived shimmering; and binocular rivalry, or an alternating perception between the views of the two eyes. In this paper, it is shown that increasing the dichoptic luminance modulation leads to these three phenomena in sequence, while increasing dichoptic contrast modulation generally only leads to perceived rotation. It is also shown that average luminance and contrast are not the deciding factors in when the three perceptual phenomena occur. Perception of luster and rivalry occur when the light bars in the grating dichoptically straddle the background luminance, with little impact of the dark bars, as demonstrated when light bars or dark bars are presented in isolation. Also when presented in isolation, perceived rotation ceases when the bars dichoptically straddle the background luminance. The deciding factor is shown not to be the adaptation level of the participant and instead to be this relation of the monocular images to the background. The patterns for perceived rotation versus binocular luster and binocular rivalry suggest separate mechanisms in the visual system. Possible mechanisms are suggested, and experimental manipulations are proposed that would discriminate between them

Spectacularly Binocular: Exploiting Binocular Luster Effects for HCI Applications

Ph.DDOCTOR OF PHILOSOPH

A search asymmetry for interocular conflict

When two different images are presented to the two eyes, the percept will alternate between the images (a phenomenon called binocular rivalry). In the present study, we investigate the degree to which such interocular conflict is conspicuous. By using a visual search task, we show that search for interocular conflict is near efficient (15 ms/item) and can lead to a search asymmetry, depending on the contrast in the display. We reconcile our findings with those of Wolfe and Franzel (1988), who reported inefficient search for interocular conflict (26 ms/item) and found no evidence for a search asymmetry. In addition, we provide evidence for the suggestion that differences in search for interocular conflict are contingent on the degree of abnormal fusion of the dissimilar images

Adaptation to interocular difference

Patterns in the two eyes' views that are not identical in hue or contrast often elicit an impression of luster, providing a cue for discriminating them from perfectly matched patterns. Here we ask whether the mechanism for detecting interocular differences (IDs) is adaptable. Our stimuli were horizontally oriented multispatial-frequency grating patterns that could be subject to varying degrees of ID through the introduction of interocular phase differences in the grating components. Subjects adapted to patterns that were either correlated, uncorrelated, monocular (one eye only), or anticorrelated. Following adaptation, thresholds for detecting IDs were measured using a staircase procedure. It was found that ID thresholds were elevated following adaptation to uncorrelated, monocular, and anticorrelated but not correlated patterns. Threshold elevation was found to be maximal when the orientations of the adaptor and test gratings were the same, and when their spatial frequencies were similar. The results support the existence of a specialized mechanism for detecting IDs, the most likely candidate being the binocular differencing channel proposed in previous studies.Canadian Institute of Health Researc

'Proto-rivalry': how the binocular brain identifies gloss.

Visually identifying glossy surfaces can be crucial for survival (e.g. ice patches on a road), yet estimating gloss is computationally challenging for both human and machine vision. Here, we demonstrate that human gloss perception exploits some surprisingly simple binocular fusion signals, which are likely available early in the visual cortex. In particular, we show that the unusual disparity gradients and vertical offsets produced by reflections create distinctive 'proto-rivalrous' (barely fusible) image regions that are a critical indicator of gloss. We find that manipulating the gradients and vertical components of binocular disparities yields predictable changes in material appearance. Removing or occluding proto-rivalrous signals makes surfaces look matte, while artificially adding such signals to images makes them appear glossy. This suggests that the human visual system has internalized the idiosyncratic binocular fusion characteristics of glossy surfaces, providing a straightforward means of estimating surface attributes using low-level image signals.This research was by the Wellcome Trust (08459/Z/07/Z; 095183/Z/10/Z), the DFG (SFB-TRR-135 "Cardinal Mechanisms of Perception") and the EU Marie Curie Initial Training Network "PRISM" (FP7-PEOPLE-2012-ITN, Grant Agreement: 316746).This is the author accepted manuscript. It is currently under an indefinite embargo pending publication by Royal Society Publishing