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Ayumi Sakai, Kazuo Fujita, Carole Parron, Joël Fagot; Ecological account for ground dominance: Comparisons between terrestrial and arboreal primates. Journal of Vision 2008;8(6):455. doi: 10.1167/8.6.455.
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© ARVO (1962-2015); The Authors (2016-present)
Recent studies have demonstrated advantages of the ground surface in 3D scene perception in humans (e.g., Bian et al., 2005, 2007; McCarley & He, 2000). These characteristics of humans may be closely linked to strong terrestriality. We have investigated how the ecological factors may influence depth perception from texture gradients. We compared humans, terrestrial baboons (Papio papio) and arboreal New World monkeys (Cebus apella and Saimili sciureus) for their perception of the size constancy illusion. The task was to classify a red disk (sample) into two size categories. In Experiment 1, the sample was placed on a textured background that depicted either “ground” or “ceiling”. Humans perceived strong size constancy illusion from texture gradients, with its magnitude larger in the “ground” context. Baboons also showed ground dominance though it is not so strong as humans'. In contrast, New World monkeys perceived the size constancy illusion but showed no ground dominance. The results indicate that primates may have a size constancy system and three-dimensional scene perception from texture gradients in common, but that only terrestrial primates might have acquired the ground dominance. In addition, human visual system might have developed the ground dominance in textured surface processing through exposure to the homogeneous plane surfaces such as floors or paved roads. In Experiment 2, New World monkeys were tested with “side-wall” backgrounds. The monkeys perceived stronger size constancy illusion in “side-wall” than in “ground” and “ceiling” backgrounds, which implies that the strategy of three-dimensional scene perception in arboreal primates may be different from terrestrial primates. The present results suggest that ecological differences give rise to differences in visual environment that may lead to diverging depth perception processes among humans, baboons and New World monkeys.
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