Change not State: Perceptual coupling in multistable displays reflects transient bias induced by perceptual change

We investigated how changes in dynamic spatial context influence visual perception. Specifically, we reexamined the perceptual coupling phenomenon when two multistable displays viewed simultaneously tend to be in the same dominant state and switch in accord. Current models assume this interaction reflecting mutual bias produced by a dominant perceptual state. In contrast, we demonstrate that influence of spatial context is strongest when perception changes. First, we replicated earlier work using bistable kinetic-depth effect displays, then extended it by employing asynchronous presentation to show that perceptual coupling cannot be accounted for by the static context provided by perceptually dominant states. Next, we demonstrated that perceptual coupling reflects transient bias induced by perceptual change, both in ambiguous and disambiguated displays. We used a hierarchical Bayesian model to characterize its timing, demonstrating that the transient bias is induced 50–70 ms after the exogenous trigger event and decays within ~200–300 ms. Both endogenous and exogenous switches led to quantitatively and qualitatively similar perceptual consequences, activating similar perceptual reevaluation mechanisms within a spatial surround. We explain how they can be understood within a transient selective visual attention framework or using local lateral connections within sensory representations. We suggest that observed perceptual effects reflect general mechanisms of perceptual inference for dynamic visual scene perception.

3D computational modeling and perceptual analysis of kinetic depth effects

Humans have the ability to perceive kinetic depth effects, i.e., to perceived 3D shapes from 2D projections of rotating 3D objects. This process is based on a variety of visual cues such as lighting and shading effects. However, when such cues are weak or missing, perception can become faulty, as demonstrated by the famous silhouette illusion example of the spinning dancer. Inspired by this, we establish objective and subjective evaluation models of rotated 3D objects by taking their projected 2D images as input. We investigate five different cues: ambient luminance, shading, rotation speed, perspective, and color difference between the objects and background. In the objective evaluation model, we first apply 3D reconstruction algorithms to obtain an objective reconstruction quality metric, and then use quadratic stepwise regression analysis to determine weights of depth cues to represent the reconstruction quality. In the subjective evaluation model, we use a comprehensive user study to reveal correlations with reaction time and accuracy, rotation speed, and perspective. The two evaluation models are generally consistent, and potentially of benefit to inter-disciplinary research into visual perception and 3D reconstruction.

Surface curvature from kinetic depth can affect lightness

The light reaching the eye confounds the proportion of light reflected from surfaces in the environment with their illumination. To achieve constancy in perceived surface reflectance (lightness) across variations in illumination, the visual system must infer the relative contribution of reflectance to the incoming luminance signals. Previous studies have shown that contour and stereo cues to surface shape can affect the lightness of sawtooth luminance profiles. Here, we investigated whether cues to surface shape provided solely by motion (via the kinetic depth effect) can similarly influence lightness. Human observers judged the relative brightness of patches contained within abutting surfaces with identical luminance ramps. We found that the reported brightness differences were significantly lower when the kinetic depth effect supported the impression of curved surfaces, compared to similar conditions without the kinetic depth effect. This demonstrates the capacity of the visual system to use shape from motion to "explain away" alternative interpretations of luminance gradients, and supports the cue-invariance of the interaction between shape and lightness.

Two Sinusoids

Multiplication of a stationary and moving sinusoids create ambiguous stimulus that, when observed, can result in five alternating perceptions and another physically plausible but hardly traceable interpretation. The most astonishing about this illusion is that using single physical stimulus creates several vivid unambiguous perceptions that may intentionally or spontaneously alternate in observer’s mind. The illusion demonstrates the brain’s active role in acquiring and processing visual information and its ability to construct 3D objects from a 2D motion. To build such visual interpretations the brain exploits several mechanisms. In the presented illusion the most noticeable strategies are a kinetic depth perception and a perceptual rivalry.