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Anna A. Kosovicheva, David Whitney; A meridional anisotropy of the flash-drag effect. Journal of Vision 2013;13(9):369. doi: https://doi.org/10.1167/13.9.369.
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© ARVO (1962-2015); The Authors (2016-present)
To effectively compare the positions of objects, especially those in dynamic scenes, the visual system may need to construct a representation of space between the objects. How does the visual system construct a representation of space between objects when they are in different visual hemifields? As input from the left and right visual fields is predominantly processed in different hemispheres, we might expect considerable differences in perceived position when the locations of objects are compared within a visual hemifield than when a comparison is made between the left and right hemifields. We tested this hypothesis using the flash-drag effect (FDE). Previous work has shown that when a briefly flashed stationary stimulus is presented near a moving object, the perceived location of the stationary stimulus is biased in the direction of motion following the flash (Whitney & Cavanagh, 2000). On each trial, subjects viewed two adjacent rectangular textured patterns (one each in the left and right visual field) moving in opposite directions (up or down), reversing direction after 380 ms. Two brief stationary flashes were presented superimposed on the moving patterns straddling the vertical meridian at the moment of the motion reversals. Subjects indicated the direction of vernier misalignment in a 2AFC task. Subjects’ responses were consistent with a large FDE, such that the perceived vernier misalignment was in the direction of motion following the flash. When the same displays were rotated 90 degrees such that the stationary flashes straddled the horizontal meridian, the FDE was reduced for all subjects, (p <.05). The visual system evidently constructs a representation of space between objects in such a way that the space is more easily distorted across the vertical than the horizontal meridian, thus revealing the challenge of reconciling relative position assignment across the hemispheres.
Meeting abstract presented at VSS 2013
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