September 2021
Volume 21, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   September 2021
Temporal integration window of the double-drift illusion: an immediate effect of the internal motion
Author Affiliations
  • Nathan H. Heller
    Dartmouth College
  • Patrick Cavanagh
    Dartmouth College
    Glendon College
  • Peter U. Tse
    Dartmouth College
Journal of Vision September 2021, Vol.21, 2642. doi:
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      Nathan H. Heller, Patrick Cavanagh, Peter U. Tse; Temporal integration window of the double-drift illusion: an immediate effect of the internal motion. Journal of Vision 2021;21(9):2642.

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      © ARVO (1962-2015); The Authors (2016-present)

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The double-drift illusion, also referred to as the infinite regress and curveball illusion, is an extreme example of a motion-induced position shift. If the internal sign-wave grating of a Gabor patch moves orthogonally to the direction of the patch, its perceived direction may be shifted by more than 50º. This shift reflects a combination of the patch and internal motions. Question: How long does it take to combine information about the internal and external motions of the doubly drifting Gabor patch. Methods: Participants reported the direction of a moving Gabor patch in either a control condition that had no internal motion, or a double-drift condition with orthogonal internal motion presented for either 8.4, 16.8, 25.2, 33.6, 42.0 or 50.4ms (2 to 12 frames at 240 Hz refresh rate). For each condition, the patch direction ranged randomly from 0º to 351º in steps of 9º. We subtracted the actual external drift direction from the reported direction and fit a Von Mises distribution to these values, averaged across subjects. Results: Already at the shortest stimulus duration, 8.4 ms, the mean of responses for the double-drift condition differs significantly from zero (62º, p<.0001), with significant clustering around that value (kappa= .51, p<.00001). At the same duration, the control responses did not differ significantly from zero (24º, p = .16) but still clustered significantly (kappa = .51, p<.00001). At longer durations, the double-drift responses remained in the range of 45º to 60º while the control responses approached 0º. Thus, even at the shortest presentation duration, the internal drift already drives perceptual reports as much as it does at longer durations. Conclusion: The illusory direction appears to be in place as soon as the double-drift stimulus appears.


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