Abstract
How does the visual system combine the two, slightly different, retinal images to arrive at a single, meaningful percept? Traditional models of stereo matching suggest that we match corresponding points in the two retinal images. However, virtually every scene around us contains regions that only one eye can access. These regions are, in these models, treated as noise and thus ignored. However, there is some evidence that they form part of our cyclopean percept of a scene (Ono et al. 2003. J. of Exp. Psych.: Gen. 132(2), 253-265), rather than appearing as rivalrous. Here, we sought to explore how items in monocular regions contribute to the representation of pattern and density. Observers viewed a stimulus comprising a random dot pattern viewed via one of 3 conditions: binocularly (all dots visible), behind a set of fence-like vertical occluders (each dot could be seen by only one eye), or behind a set of horizontal occluders (each dot was binocularly visible but only 50% of the dots were visible in total).
In a 2AFC, relative numerosity task, participants were asked to indicate which one of two stimuli was more numerous. We measured thresholds and biases. There was no significant difference between thresholds in the vertical and horizontal occluder conditions, suggesting that monocular regions are not seen as rivalrous. We found no significant bias for any of the conditions. Our results are consistent with the hypothesis that monocular regions contribute fully to the representation of pattern and density.
