Testing Theories of Visual Position Perception by Manipulating Magnocellular Processing for Various Motion Trajectories
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Spatial projection theories of visual localization posit that a moving stimulus’ perceived position is projected forwards in order to compensate for processing delays (Eagleman & Sejnowski, 2007; Nijhawan, 2008). Temporal integration theories (Krekelberg & Lappe, 2000) suggest that an averaging over positions occupied by the moving stimulus for a period of time is the dominant process underlying perception of position. Contrary to the predictions of these theories, reducing magnocellular (M) pathway processing by making stimuli equiluminant, and adding luminance noise (see Fig. 1A), had the opposite effect on localization judgments, assessed via the flash-lag illusion, when a smooth, continuous trajectory was used, compared to when the moving object suddenly appeared, or suddenly reversed direction (Fig. 1B, for interaction, F[2, 22] = 59.91, p = 1.3 × 10-9, eta_P^2 = .85). In addition, we have preliminary data indicating that simply reducing the contrast of the moving stimulus, without adding luminance noise, also yields a cross-over interaction similar to that shown in Fig. 1B. In order to explain the perception of the position of moving objects across all trajectories, our cross-over interaction result necessitates processes additional to those proposed by either the spatial projection or temporal integration theories. It also calls into question the utility of the onset and reversal trajectories for testing theories of localization for continuous trajectories.
Frontiers in Human Neuroscience Conference Abstract : ACNS-2012 Australasian Cognitive Neuroscience Conference.
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Psychology and Cognitive Sciences