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Yuki Kawashima, Kazuho Fukuda, Hirohiko Kaneko, Yasuki Yamauchi, Keiji Uchikawa; Additivity of vection speed induced by fast and slow spatially-overlapped optical flows. Journal of Vision 2013;13(9):955. doi: 10.1167/13.9.955.
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© ARVO (1962-2015); The Authors (2016-present)
When two optical flows, expanding at different speeds, are overlapped in the visual field, the perceived vection speed cannot merely be predicted by our previous knowledge on the speed of the optical flows. In this study we investigated how the perception of the vection speed is affected when we encounter two expanding optical flows of different speeds. Two expanding optical flows, composed of 1000 random dots in total, were presented on a hemisphere-screen producing a wide visual field of 120 deg. The dots spread in 3D space with binocular disparity. We used the difference in speed between two optical flows as the experimental condition. In each condition, we varied the ratio of the numbers of random dots expressing two optical flows: fast and slow optical flow. Subjects estimated the perceived vection speed arisen from two optical flows. Fifteen subjects participated in the experiments. When the speed difference between two optical flows was small, the results showed that the perceived vection speed linearly increased with the ratio of the fast random dots. On the other hand, when the speed difference was large the slow random dots worked as a dominant cue to determine the vection speed. In order to explain these characteristics of vection speed when two optical flows coexist, we developed a non-linear model in which the vection speed was predicted by power summation of the individual vection speeds, which were derived in the condition where only one of the optical flows was presented. The ratio of the number of the random dots used to present each optical flow serves as a weighting factor. This model well describes the experimental results.
Meeting abstract presented at VSS 2013
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