Integration of 3D structure from disparity into biological motion perception independent of depth awareness

The gender-based facing bias in 3-D biological motion perception

In biological motion perception, movements of several point lights can evoke a vivid impression of living animals, including humans. Recent studies have reported that male point-light walkers tend to be perceived as facing toward the viewer more than female walkers, and have hypothesized that the gender-based facing bias arises from motion signals. The purpose of this study was to test this hypothesis under experimental conditions where binocular disparity was added to biological motion stimuli. In the two experiments reported here, participants were presented with disparity-defined female and male point-light figures facing toward or away from the viewer. In Experiment 1, we measured "facing-the-viewer" responses in upright and inverted walker configurations. It was found that the facing bias was greater for the male walker than for the female walker in most disparity magnitudes, regardless of walker inversion. In Experiment 2, the walker stimuli were replaced by static snapshots of the walkers. The results showed that the facing bias did not differ between the female and male static figures. These results suggest that motion signals play an important role in producing the gender-based facing bias, even when binocular disparity is added to biological motion stimuli.

The interaction of perceptual biases in bistable perception

When viewing ambiguous stimuli, people tend to perceive some interpretations more frequently than others. Such perceptual biases impose various types of constraints on visual perception, and accordingly, have been assumed to serve distinct adaptive functions. Here we demonstrated the interaction of two functionally distinct biases in bistable biological motion perception, one regulating perception based on the statistics of the environment – the viewing-from-above (VFA) bias, and the other with the potential to reduce costly errors resulting from perceptual inference – the facing-the-viewer (FTV) bias. When compatible, the two biases reinforced each other to enhance the bias strength and induced less perceptual reversals relative to when they were in conflict. Whereas in the conflicting condition, the biases competed with each other, with the dominant percept varying with visual cues that modulate the two biases separately in opposite directions. Crucially, the way the two biases interact does not depend on the dominant bias at the individual level, and cannot be accounted for by a single bias alone. These findings provide compelling evidence that humans robustly integrate biases with different adaptive functions in visual perception. It may be evolutionarily advantageous to dynamically reweight diverse biases in the sensory context to resolve perceptual ambiguity.

Quality Index for Stereoscopic Images by Separately Evaluating Adding and Subtracting

The human visual system (HVS) plays an important role in stereo image quality perception. Therefore, it has aroused many people’s interest in how to take advantage of the knowledge of the visual perception in image quality assessment models. This paper proposes a full-reference metric for quality assessment of stereoscopic images based on the binocular difference channel and binocular summation channel. For a stereo pair, the binocular summation map and binocular difference map are computed first by adding and subtracting the left image and right image. Then the binocular summation is decoupled into two parts, namely additive impairments and detail losses. The quality of binocular summation is obtained as the adaptive combination of the quality of detail losses and additive impairments. The quality of binocular summation is computed by using the Contrast Sensitivity Function (CSF) and weighted multi-scale (MS-SSIM). Finally, the quality of binocular summation and binocular difference is integrated into an overall quality index. The experimental results indicate that compared with existing metrics, the proposed metric is highly consistent with the subjective quality assessment and is a robust measure. The result have also indirectly proved hypothesis of the existence of binocular summation and binocular difference channels.