December 2022
Volume 22, Issue 14
Open Access
Vision Sciences Society Annual Meeting Abstract  |   December 2022
Is The Double-Drift Illusion Special?
Author Affiliations & Notes
  • Sharif Saleki
    Dartmouth college
  • Ineke Cordova
    Carleton College, Northfield, MN, USA
  • Patrick Cavanagh
    Dartmouth college
    Glendon College, Toronto, ON, Canada
    York University
  • Peter Tse
    Dartmouth college
  • Footnotes
    Acknowledgements  This material is based upon work supported by the National Science Foundation under Grant #1632738.
Journal of Vision December 2022, Vol.22, 4214. doi:
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      Sharif Saleki, Ineke Cordova, Patrick Cavanagh, Peter Tse; Is The Double-Drift Illusion Special?. Journal of Vision 2022;22(14):4214.

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

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A stationary Gabor with an internal drift induces an illusory displacement in perceived position (DeValois & DeValois, 1992). When the Gabor also drifts orthogonally to this internal motion, its trajectory dramatically deviates from its real path (Saleki et al., 2021). It has been suggested that the external motion of this double-drift stimulus plays a critical role in allowing the accumulation of position offset to continue over several hundreds of milliseconds (Cavanagh and Tse, 2019). Here, we compared the illusory offset of the stationary Gabor (with only horizontal internal drift: the single-drift) to that of the double-drift stimulus (with additional vertical drift) presented at the same eccentricity (10.8 dva). We collected reports of the perceived length and orientation of the Gabor’s trajectory by the method of adjustment. In the constant-speed block (where internal speed was fixed at 5 Hz and the path duration ranged from 50 to 800 ms on different trials), duration had a significant effect on the illusory horizontal offset seen for both types of stimuli (p<.001), but there was no difference between stimulus types. In the constant-duration block (path duration fixed at 500 ms, internal speed varied from 2 to 6 Hz), reports of the horizontal offset for both the single- and double-drift stimulus increased with the internal speed (p<.001), with the single-drift stimulus having an overall greater effect (p=.04). These results suggest that the dynamics of single- and double-drifting Gabor patches are comparable under the same viewing conditions, and that a single-drifting Gabor viewed in the periphery can accumulate illusory position shifts that are as large as those of the double-drift. Unlike previous studies of the single drift (e.g., Chung et al., 2002) where the drift saturated within 100 ms, the illusory shifts in the periphery here accumulated for durations of up to 800 ms.


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