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Oliver Flynn, Arthur G. Shapiro; Integration of motion signals in the absence of changes in spatial position. Journal of Vision 2012;12(9):1226. doi: https://doi.org/10.1167/12.9.1226.
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© ARVO (1962-2015); The Authors (2016-present)
A moving object produces multiple motion signals at its edges; the visual system must organize (i.e., group) the motion signals associated with the object even though these signals can be separated over a considerable distance. Here we present a novel stimulus configuration for assessing the visual system’s ability to organize disparate motion signals into the perception of illusory object motion. The stimulus for the first experiment consisted of a diamond (4.7 deg diagonal, static 50 cd/m2) bordered by four thin edges (.21 deg) and square background (14 deg); the luminance of the edges and the background modulate at 3 Hz. Similar to reversed-phi, motion signals are produced by phase differences between the modulation of the edges and background. Even though the diamond is physically stationary, it will appear to move upwards when the modulation for the top edges phase-leads the background and the modulation of bottom edges phase-trails the background (the diamond moves downward when the phase relationships are reversed). We measured an observer’s ability to detect the direction of the diamond’s motion as a function of 19 parametric phase combinations of edges and background at four modulation amplitudes. The four observers detected the object motion on a higher proportion of trials when the phase differences between edges and background increased and were able to consistently detect object direction with as subtle as a 10 deg phase shift between edge and background. Further demonstrations illustrate that luminance noise does not disrupt object motion as long as the phase relationship between edges and background remains the same. Conclusion: We introduce a powerful (and visually dramatic) new method for measuring motion integration and show that the visual system can integrate extraordinarily fine differences in temporal phase over large spatial distances.
Meeting abstract presented at VSS 2012
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