Isolating cues to sex and quantifying their relative influence on perception during binocular rivalry

Graeme Hacker

doi:10.25918/thesis.206

It is generally understood that visual perception relies on complex combinations of both low-level processes involved in physical feature detection, as well as high-level cognitions informed by our prior experiences with the environment. There is a visual phenomenon which occurs when two different images are simultaneously presented to each eye separately. Rather than the observer perceiving the two images superimposed, the brain focuses on one of the images for a few seconds before alternating to the other. After a few more seconds the perceived image alternates again. This is referred to as Binocular Rivalry. A debate in the binocular rivalry literature is whether these alternations are governed by low-level or high-level cognitions. To explore this question, I used Point Light Walker (PLW) stimuli. These are images made up of 15 dot points which represent the head, shoulders, pelvis, major body joints, and extremities of a human figure. Evidence that these images activate high-level processing areas of the brain which identify biological motion and sex identification is important. They are only made from low-level cues (dot points) combined with structural information and biological motion. I explored these individual cues using a binocular rivalry paradigm to assess which features would influence the reported alternation patterns. Total durations were recorded by participants indicating which of the two images was exclusively visible at any given moment. I employed PLWs from a continuum previously described as varying on stereotypical male and female features. I found that ‘male’ PLWs predominated for longer average durations than ‘female’ or neutral PLWs (experiment 1), stepwise reduction of ‘maleness’ reduced the size of the bias in a step-wise manner (experiment 2), larger ‘male’ PLWs predominated for longer than the smaller ‘male’ PLW (experiment 3), and there were no significant differences in predominance durations between the ‘female’ PLW subtypes (experiment 4). The structural and kinematic cues of the ‘male’ PLW appeared to moderate the bias (experiment 5) and inverting the PLWs did not reduce the bias as would be expected if top-down processes were causing the effect (experiment 6). Finally, significant differences were observed between the low-level features of the ‘male’ and ‘female’ PLWs which corresponded with the findings from experiments 1, 3, and 4 (experiment 7). Considered together, I determined that the binocular rivalry alternations in these experiments, were driven by both low-level and high-level features of the PLW stimuli. A summary outlining the influence of each of the PLW features, on the average rivalry durations, is offered in the conclusion.

Isolating cues to sex and quantifying their relative influence on perception during binocular rivalry

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Isolating cues to sex and quantifying their relative influence on perception during binocular rivalry

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