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Patrick Cavanagh, Stuart Anstis; Paradoxical frame stabilization for flashed but not continuous probes. Journal of Vision 2021;21(9):2054. doi: https://doi.org/10.1167/jov.21.9.2054.
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© ARVO (1962-2015); The Authors (2016-present)
Moving frames have previously been shown to produce large displacements in the perceived location of flashed probes (Cavanagh, Anstis, & Wexler, VSS 2020). Here the moving frame’s effect on flashed probes is compared to its effect on a continuously moving probe. In the flashed case, the first flash was presented before and the second probe after the frame’s motion. The results showed that across a 22° range of offsets between the probes, their perceived separation always discounted the frame’s motion: the perceived positions were the locations each probe had in the frame when flashed, but seen as if the frame were stationary. That included the case where the two probes were far apart on the screen but at the same location in the frame. Here the probes were perceived at the same location in the world despite their 10° physical separation on the screen. This simulates the conditions of eye movements where an object is at the same position in the visual scene before and after the movement and do not appear to have moved despite the large displacement on the retina. We also tested a continuous motion condition where a single probe moved continuously up and down while the frame moved left and right. This is the classic stimulus for induced motion (Wallach, Bacon, & Schulman, 1978) and the results were very different from those with the flashed probes. The apparent direction of the probe was significantly influenced by the frame, but by only about 1/5th the amount seen for the flashed probes. It is likely that the continued presence of the probe during the frame’s motion provided evidence of its physical path that reduced the frame’s effect compared to that seen for the flashed probes.
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