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Visual search for motion-in-depth: stereomotion does not 'pop out' from disparity noise

An Erratum to this article was published on 01 August 1998


In a visual search task, targets defined by motion or binocular disparity stand out effortlessly from stationary distractors (`pop-out'), suggesting that target and distractors are processed by different neural mechanisms. We used pop-out to explore whether motion directly toward or away from the observer (z-motion) is detected using binocular motion cues. A target moving laterally (x-motion) popped out amid stationary distractors with binocular disparity, but z-motion did not pop out. However, a small x-motion added to the target's z-motion caused it to pop out. We therefore suggest that the visual system may not be specifically sensitive to binocular motion differences.

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Figure 1: Experimental design.
Figure 2: Percent correct for detecting the interval containing the moving target dot for two observers, SPM and SNW.
Figure 3: Percent correct as a function of the number of distractors for x-motion amid 2D distractors () and z-motion amid 3D distractors (•).
Figure 4: Percent correct as a function of the number of distractors in three experimental conditions for two observers.


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We thank Bruce Cumming, Simon Rushton, Harvey Smallman, Jane Sumnall and Preeti Verghese for comments on the manuscript. The work was supported by a UK MRC grant G9533618N to JMH and AFOSR grant F49620-95-1-0265 to SPM.

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Correspondence to Julie M. Harris.

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Harris, J., McKee, S. & Watamaniuk, S. Visual search for motion-in-depth: stereomotion does not 'pop out' from disparity noise. Nat Neurosci 1, 165–168 (1998).

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