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Pascal Mamassian, Wendy J. Adams; Motion-induced masking. Journal of Vision 2002;2(7):391. doi: 10.1167/2.7.391.
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Introduction: The location of moving objects can be misperceived in the direction of motion. This mis-localisation is believed to derive from mechanisms that compensate for the processing time of motion signals (Ramachandran and Anstis, 1990). We investigate whether a moving object masks a stationary target that is presented next to it.
Methods: Two random dot kinematograms (RDKs) were presented at 3 deg above and below a fixation cross. One RDK moved to the left while the other moved to the right. Both RDKs were modulated by a Gaussian envelope in space and time. Even though the Gaussian envelope was stationary, each RDK was perceived as displaced in its direction of motion (De Valois and De Valois, 1991). On each trial, a small target was placed either to the left or right of one of the two RDKs. The contrast of the target was varied. Observers had to report the location (4AFC) of this briefly presented target.
Results: We measured detection thresholds for the target. Despite the fact that the targets were presented at a fixed distance away from the centre of the RDKs, targets were usually easier to perceive when they were behind rather than in front of the RDK.
Discussion: Our results show that moving objects interfere with the perception of other, stationary objects in a scene. One possible explanation for these results is that the moving and stationary objects are competing for a common position in perceptual space — the static target is perceived near its true location, while the moving object is mis-localised, causing masking or crowding.
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