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Jin Qian, Saumil S. Patel, Harold E. Bedell; Effects of spatial frequency, contrast, and stimulus size on the magnitude of perceived depth and speed. Journal of Vision 2006;6(6):653. doi: 10.1167/6.6.653.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose. To investigate if similar neural processing underlies the perception of stereoscopic depth and motion, the effects of spatial frequency, contrast, and stimulus size on the perceived magnitude of suprathreshold depth and speed were studied using identical stimuli. Method. To assess perceived depth, Gabor pairs with different phase disparities were presented simultaneously for 167 ms at a distance of 1 m. In different blocks of trials, the test stimuli had a spatial frequency of 1 to 4 c/deg, a contrast of 3 to 50%, and a size of 1 to 4 deg. The subjects (N=2) free fused and reported if the test stimulus was further from or closer to the reference plane than a comparison stimulus - a black-white edge that varied in disparity from trial to trial according to a staircase. The stimuli used to assess perceived speed were identical, except they were presented successively to produce two-frame apparent motion. The subjects reported if the speed of the test stimulus was faster or slower than the comparison moving edge. Results. Across subjects, the perceived depth and speed of the test stimulus varied idiosyncratically with spatial frequency. However, for both subjects perceived depth was independent of stimulus contrast and size, whereas perceived speed increased systematically with the contrast and size of the test stimulus. Conclusion. The dissimilar effects of changing stimulus contrast and size on the perception of suprathreshold depth and speed indicate that distinct neural processing underlie the perception of stereoscopic depth and motion.
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