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M. J. Kearns, W. H. Warren, M. J. Tarr, A. P. Duchon; Does optic flow contribute to human path integration?. Journal of Vision 2001;1(3):134. doi: 10.1167/1.3.134.
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Path integration involves updating one's position and orientation based on information about self-motion, e.g. from optic flow or the body senses (vestibular information, proprioception, efference). In the human navigation literature, there is evidence that people can use the body senses for path integration while walking without vision (Loomis, et al 1993) and use optic flow when the body senses are unavailable, as in a joystick task (Peruch, et al 1997, Riecke, et al 2000, Bud, 2000). However, when both types of information are available, the body senses appear to dominate (Bud, 2000). To dissociate optic flow and the body senses in a triangle completion task, we manipulated the optic flow rate during active walking in an immersing virtual environment. The visual gain was either greater than (150 percent), lower than (67 percent), or the same (100 percent) as in normal walking. Gains for observer translation and rotation were manipulated separately. In Exp. 1, the body senses played a strong role, but the influence of optic flow was indeterminate because the visual gain covaried with the physical size of the walked triangle. We eliminated this covariation in Exp. 2 and found that, although the body senses dominate performance, there is also a small contribution of optic flow. We are currently investigating whether the addition of landmarks increases the visual contribution to path integration.
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