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Tomoko Imura, Masaki Tomonaga; Visual search on the ground-like surface defined by texture gradients in chimpanzees (Pan troglodytes) and humans (Homo sapiens). Journal of Vision 2007;7(9):284. doi: 10.1167/7.9.284.
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© ARVO (1962-2015); The Authors (2016-present)
Previous studies of visual search have shown that in humans, visual attention is distributed over a three-dimensional surface defined by binocular disparity (He and Nakayama, 1995), and pictorial depth cues (Morita and Kumada, 2003). Although nonhuman primates are sensitive to pictorial cues (Imura and Tomonaga, 2003), few studies explored the relationship between pictorial depth perception and visual attention from the comparative perspective. In this study, we examined how chimpanzees and humans searched on the ground-like surface defined by texture gradients.
Experiment 1 tested the effects of ground surface on visual search. Participants were required to touch a cube with odd color (target) among those arranged at an imaginary ground-like surface. Under the top-difference condition, a cube with dark gray top face defined as target and distractor cubes with white top face were presented as a search display. Under the side-difference condition, a cube with dark gray side face (target) and cubes with white side face (distractors) were presented. Both chimpanzees and humans detect the target faster under the top-difference condition than under the side-difference condition, suggesting that a ground-like surface defined by texture gradients was effective for a search in both species. Experiment 2 assessed the effects of ceiling-like surface consisted of upside-down cubes on search performances. Both species showed faster detection of the target in the side-difference condition than in the top-difference condition, suggesting that asymmetry of the search for top faces to side faces disappeared on the ceiling-like surface.
The findings of these two experiments indicate that in both chimpanzees and humans, a ground-like surface defined by texture gradients facilitated the search for objects on it, while a ceiling-like surface did not. Our findings suggest the ground dominance effect for search in both species.
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