Natural images dominate in binocular rivalry

Abstract

Ecological approaches to perception have demonstrated that information encoding by the visual system is informed by the natural environment, both in terms of simple image attributes like luminance and contrast, and more complex relationships corresponding to Gestalt principles of perceptual organization. Here, we ask if this optimization biases perception of visual inputs that are perceptually bistable. Using the binocular rivalry paradigm, we designed stimuli that varied in either their spatiotemporal amplitude spectra or their phase spectra. We found that noise stimuli with ''natural'' amplitude spectra (i.e., amplitude content proportional to 1/f, where f is spatial or temporal frequency) dominate over those with any other systematic spectral slope, along both spatial and temporal dimensions. This could not be explained by perceived contrast measurements, and occurred even though all stimuli had equal energy. Calculating the effective contrast following attenuation by a model contrast sensitivity function suggested that the strong contrast dependency of rivalry provides the mechanism by which binocular vision is optimized for viewing natural images. We also compared rivalry between natural and phase-scrambled images and found a strong preference for natural phase spectra that could not be accounted for by observer biases in a control task. We propose that this phase specificity relates to contour information, and arises either from the activity of V1 complex cells, or from later visual areas, consistent with recent neuroimaging and single-cell work. Our findings demonstrate that human vision integrates information across space, time, and phase to select the input most likely to hold behavioral relevance.amplitude spectrum ͉ interocular suppression ͉ natural image statistics ͉ phase spectrum ͉ bistable perception T he human visual system is tasked with processing and organizing perceptual information relevant to the tasks we routinely perform. Recent investigations of the statistical properties of natural images indicate that the tuning characteristics of early visual mechanisms reflect measurable properties of the world (1). From simple image attributes such as luminance and contrast information (2) to Gestalt rules of perceptual organization such as proximity and good continuation (3, 4), known properties of perceptual systems appear tuned to the statistics of natural images (5-8). As a whole, these studies support the hypothesis that human visual processing has evolved to efficiently encode images from our natural environment (see ref. 1 for a recent review). Here, we directly address this hypothesis by asking if, when the visual system must choose between two competing inputs, it prefers the one most representative of the natural environment.During binocular rivalry, conscious perception alternates between different images presented to the two eyes. It is well established that some stimuli are preferred to others, for example, high-contrast stimuli will dominate over low-contrast stimuli, and thus will be ...

Perceptual Organization and Consciousness

“…Even if we assume that this effect may in some way be influenced by low level image properties (an explanation which is somewhat unlikely due to the diverse range of natural stimuli used in that study) and bypasses detailed visual analysis through different pathways, it must require some complex processes to identify the out-ofplace features. This finding is in some way contrary to the aforementioned reports of a bias for more "natural" stimuli to dominate in binocular rivalry (Baker and Graf 2009). However, as discussed in the previous section it is also important to note that the measure used by this study, time to emergence from CFS, may not truly reflect the processing that occurs under suppression but the detection of incongruent scenes at the moment of transition between suppression and visibility, which in turn results in them reaching perceptual dominance with a faster speed.…”

“…At an even more basic level, image statistics vie for perceptual dominance. When one eye views white noise images, while the other views noise images filtered to fall within the 1/f spectrum typically observed in natural scenes (Field 1987;Simoncelli and Olshausen 2001), the latter dominate perception for a significantly longer periods than the white noise images (Baker and Graf 2009). This may suggest that the visual system selectively responds by bringing stimuli whose image statistics conform with the natural world to the focus of awareness.…”

Can binocular rivalry reveal neural correlates of consciousness?

“…But the methodological point remains indisputable: the oftused mimic procedure is not perceptually equivalent to genuine rivalry alternations. In principle, this problem can be reduced by devising more realistic simulations of rivalry that include periods of mixed dominance using cross-faded blends as well as waves that originate at unpredictable locations and spread smoothly to produce a complete alternation [43][44][45]. However, nobody has yet devised a mimic condition so realistic that an informed observer might mistake it for rivalry.…”

United we sense, divided we fail: context-driven perception of ambiguous visual stimuli

“…Natural images are reported to be dominant over unnatural images in binocular rivalry [84], as are images of emotional over (more) neutral faces or scenes [85][86][87] and upright faces over inverted ones [88]. The personal preferences or mental condition of the observer [89 -91], as well as their cultural background or religion can also influence particular forms of rivalry [92].…”