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Christopher R. L. Cantor, Clifton Schor; Modeling the Flash Pulfrich Effect. Journal of Vision 2007;7(15):55. doi: 10.1167/7.15.55.
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Both brightness and exposure duration introduce biases into the spatial localization of moving objects. The perceived position of a dimmer object lags its brighter counterpart (Hess Effect). Likewise, a briefly-visible (flashed) object lags a more-continuously presented object (Flash Lag Effect or FLE). These mislocalizations have consequences for binocular vision. A zero-disparity moving object presented with unequal luminance in the two eyes produces illusory depth (Pulfrich Effect). And we recently discovered that exposing the two eyes half-images for unequal temporal durations also produces illusory depth (Flash Pulfrich Effect or FPE). Since perceived relative offsets in the monoptic stimuli become disparities under dichoptic viewing, these effects are likely to occur early in the visual system. We have developed a computational model based on magnocellular LGN neurons that can generate all 4 effects. We test the model in two FPE configurations. In the flash-initiated condition (FIC), onsets of short and long duration half-images are synchronized, whereas in the flash-terminated condition (FTC), the offsets coincide. The FLE literature suggests that the FIC produces larger effects than the FTC. Our model suggests the opposite and results confirm its prediction.
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