September 2015
Volume 15, Issue 12
Vision Sciences Society Annual Meeting Abstract  |   September 2015
Shape distortion illusion of flashed circles can be induced by dichoptic stimulation
Author Affiliations
  • Kenzo Sakurai
    Department of Psychology, Tohoku Gakuin University
  • William Beaudot
    Division of Human Informatics, Graduate School of Tohoku Gakuin University
Journal of Vision September 2015, Vol.15, 528. doi:
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      Kenzo Sakurai, William Beaudot; Shape distortion illusion of flashed circles can be induced by dichoptic stimulation. Journal of Vision 2015;15(12):528.

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

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Flash presentation of a circle alternating with its inward gradation pattern induces an illusory shape distortion: the circle appears as a polygon (e.g. hexagon) in a short period (Sakurai, 2014 VSS, ECVP). We investigated whether this shape distortion illusion occurs before or after binocular combination in the visual pathway by measuring the induction time (latency) of the illusion in dichoptic and monoptic stimulation conditions. Stereoscopic stimuli consisted of a circle of 3.5 deg in diameter and its inward gradation pattern on a white background, alternating at 2 Hz and located at 4.5 deg on the left or right side of a central fixation cross surrounded by a 15 deg square frame for fusion lock. In the dichoptic condition, the circle was presented to one eye and the gradation pattern was presented to the other eye. In the monoptic condition, both the circle and the gradation pattern were presented to the same eye. In the control condition, the circle was solely presented to one eye flashing at 2 Hz. Observers had their head fixed on a chin-and-forehead rest and viewed the display through a mirror stereoscope. They were asked to press a response key as soon as they noticed the shape distortion in each trial. Results showed that the latencies of this illusion in both dichoptic and monoptic conditions were shorter than that in the control condition. No significant difference in latency was found between the dichoptic and monoptic conditions. These results suggest that the shape distortion illusion occurs after binocular combination and that some cortical process responsive to curvatures is involved in this illusion.

Meeting abstract presented at VSS 2015


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