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Chien-Te Wu, Michèle Fabre-Thorpe, Rufin VanRullen; Time distorts space in both directions during apparent motion. Journal of Vision 2010;10(7):826. doi: 10.1167/10.7.826.
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© ARVO (1962-2015); The Authors (2016-present)
Just like Heisenberg's uncertainty principle in quantum physics, it is notoriously difficult for our visual systems to accurately determine both the timing and the position of moving objects. Previous literature has consistently shown that the perceived position of objects is influenced by their own motion or the neighboring motion context. Interestingly, all the reported phenomena (e.g., Frölich effect, motion induced position shift, flash-lag effect, etc) correspond to spatial mislocalization along the direction of motion. Here we report that a simple temporal manipulation during an apparent motion sequence can also cause the moving object to be mislocalized in the direction opposite to the motion. A single dot was displaced at a constant speed (apparent motion, 80 ms/step) across 10 locations equally distributed on an imagery circle at 2.5 degrees eccentricity. While the remainder of the sequence was kept constant on each trial, at one “critical” location we modified either the onset latency of the dot (keeping its position constant), its spatial position (keeping its onset latency constant) or both dimensions together (keeping its speed constant); we asked observers (N=8) to report the critical dot's perceived location relative to a static landmark. The most interesting finding was obtained from the onset latency manipulation: when the dot was presented too early in time, participants perceived it as ahead of the critical location; but when the dot was presented too late, participants tended to perceive it as trailing the critical location, i.e., in the direction opposite to the motion sequence. The influence of timing manipulations on perceived space was found to be about 35% of the equivalent spatial manipulations. This time-based illusory distortion of space may be due to a recalibration mechanism, whereby internal representations of the global motion context are regularly compared to external information.
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