Abstract
When dissimilar images are presented to corresponding retinal locations, perception will alternate between the two. This phenomenon is called binocular rivalry. Perceptual alternations during binocular rivalry will typically start at isolated locations and continue in gradual, wave-like fashion termed ‘traveling waves of perceptual dominance’.
Recently, Paffen, Naber and Verstraten (2008) showed that local stimulus features influence the starting point of a traveling wave. It was suggested that perceptual alternations start at the location where saliency of the suppressed image is higher than that of the dominant one. Here we investigate this suggestion.
Two images containing 81 Gabors aligned on a grid were presented dichoptically. One of the images contained vertically oriented Gabors (the suppressor); the other image obliquely oriented Gabors (the target). In order to vary local saliency, one of the Gabors in the target image contained an orientation orthogonal to its neighbors in 50% of the trials. At the start of a trial, the suppressor was presented at full contrast, while the contrast of the target was gradually increased from 0 to 100% contrast. The task of the observer was to click a mouse button as soon as the target became visible. Next, the observer indicated at what location the target became visible. Prior to a perceptual alternation, subjects were unaware of the location of the orthogonal Gabor in the target image.
The results show that perceptual alternations most often started at the salient location in the suppressed image. These results suggest that saliency information determines the starting location of perceptual alternation. Furthermore, our results are in agreement with the claim that saliency information is available at a monocular level, outside of perceptual awareness.