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Isabelle Legault, Jocelyn Faubert; Biological motion perception: Walker distance does not matter. Journal of Vision 2008;8(6):905. doi: https://doi.org/10.1167/8.6.905.
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© ARVO (1962-2015); The Authors (2016-present)
Human ability to perceive biological motion pattern is well established. Furthermore, it has been shown that observers' performances for detecting biological motion patterns in noise are worse when the walker pattern is inverted. The purpose of the present study was to determine if there is a difference between performances when biological motion patterns, in an upright and inverted orientation, are disposed at different distances in virtual space. To create our setup, we used a full immersive virtual reality environment (CAVE), giving the observers the experience of stereoscopic vision. We used a biological motion pattern composed of 13 dots, walking left or right on a treadmill. The size of the walker was 1.80 meters disposed at a virtual distance from the observer of 4, 8 and 16 meters subtending 24, 12 and 6 degrees of visual angle respectively. Using a staircase procedure, the observer's task was to identify the walker's direction (left or right) in upright and inverted conditions. The walker was presented in a scrambled mask, where the noise dot density was increased with two successive correct answers. The scrambled mask was generated by randomly selecting dots with biological motion patterns and repositioning them in 3D space. The results showed that distance does not influence performance. In other words, biological motion detection in noise, in upright and inverted conditions, does not depend on how far the walker is positioned in 3D space.
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