August 2023
Volume 23, Issue 9
Open Access
Vision Sciences Society Annual Meeting Abstract  |   August 2023
Are crossed and uncrossed disparities processed by the same mechanism?
Author Affiliations
  • Penghan Wang
    McGill University
  • Alexandre Reynaud
    McGill University
  • Robert Hess
    McGill University
Journal of Vision August 2023, Vol.23, 5660. doi:
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      Penghan Wang, Alexandre Reynaud, Robert Hess; Are crossed and uncrossed disparities processed by the same mechanism?. Journal of Vision 2023;23(9):5660.

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

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Stereopsis allows us to judge whether objects are “in front” or “behind” each other. However, it is still not clear whether this ability to judge position in depth is harnessing the same mechanism whether the stimulus is “popping in” (crossed disparity) or “popping out” (uncrossed disparity). We used a paradigm called "2-by-2 forced-choice paradigm". This paradigm involved two intervals of presentations - the target stimulus and noise. Subjects would indicate in which interval the stimulus appeared and judge whether the stimulus was crossed or uncrossed. So, we could record when the subject sees the stimulus (detection) and recognizes the stimulus (discrimination). We observed great inconsistency among people: Some participants showed strong bias towards cross or uncrossed disparity, some didn’t reach 100% identification performance even at large disparities and, surprisingly, some showed better discrimination than detection performance. Such higher discrimination rate could be explained by a Thurstonian model in which all disparities, crossed and uncrossed would be represented on a same axis. As a qualitative task, this would reveal an unconscious identification of the stimuli.


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