Orangutan Vision, Looking Preferences, and Passive Looking-Time Versus Active Touchscreen Paradigms
Adams, Laura Catherine
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Key aspects of orangutan picture preference, looking paradigms, and vision were assessed in three manuscripts. These studies have important contributions to research on comparative vision and animal picture perception, as well as practical applications for orangutan research. The first manuscript assessed visual preferences for pictures of primates. Orangutan looking-time was coded as they watched simultaneous slideshows on two laptop computers. Orangutans preferred photographs of unfamiliar orangutans over unfamiliar humans, and familiar orangutans over unfamiliar orangutans. When comparing familiar orangutans, they preferred adults over infants, and males over females. These preferences were then compared to preferences reported across primates which show variable results, likely due to complex social factors and context. A second manuscript assessed passive looking-time and active touchscreen paradigms. Passive and active paradigms can produce discrepant results, and the validity of these paradigms had not been empirically assessed in animals. Three methods were compared: looking-time at slideshows on two laptops, a touchscreen that displayed pictures when touched, and simply holding up pairs of printed images. All three methods detected the expected preference for pictures of animals over non-animals. This can be considered evidence of the reliability of these paradigms, equivalence of passive and active methods, and support for continued use of looking-time and touchscreens in orangutan research. The final manuscript assessed the contrast sensitivity function (CSF). Orangutans were trained to select vertical or horizontal lines, and then the CSF threshold was estimated by increasing the spatial frequency and decreasing the contrast of the stimuli. Orangutan CSF was similar in shape and position on the frequency scale to those of humans and macaques, but overall sensitivity was lower. We propose that this was due to testing conditions and low motivation. Across these three manuscripts orangutans demonstrated overall vision and looking behaviour that was similar to humans, however with high variability likely due to competing interests, low motivation, and individual differences.