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Lisa O'Kane, Paul Hibbard; Contextual disparity variation does not influence distance scaling in a three-dimensional shape judgement task. Journal of Vision 2008;8(6):843. doi: 10.1167/8.6.843.
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© ARVO (1962-2015); The Authors (2016-present)
Binocular disparity varies approximately inversely with the square of distance. This relationship could potentially be exploited by the visual system as a cue to viewing distance, which could be useful in the interpretation of the shape and size of objects. Previous work has suggested that the range of disparities presented to an observer might be used as a cue to distance, and therefore might influence the perception of three-dimensional shape (Glennerster et al,1998). We extend this idea by examining the effect of the magnitudes of disparity information available in the surround onperceived depth from disparity. The stimulus consisted of three dots vertically aligned on the screen. The distance in depth of the central dot from the other two was defined by disparity, and was adjusted by the observer until it appeared equal in length to the base of the triangle. The triangle was surrounded by a surface that was sinusoidally modulated in depth. Shape settings were made for different magnitudes of disparity variation in the surround, over a range of viewing distances. Observers added more depth to the stimulus at further distances than at the closer distance. However, observers' settings did not change with the pattern of disparity present in the local reference surface. We conclude that the degree of disparity variation in a local reference frame, despite providing a potential source of statistical information to distance, does not affect settings of depth made by observers.
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