Dependence of Motion Repulsion
and Rivalry on the Distance between Moving Elements
Nestor Matthews, Bard J. Geesaman, and Ning Qian, Vision Research,
2000, 40:2025-2036.
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Abstract
We investigated the extent to which motion repulsion and binocular
motion rivalry depend on the distance between moving elements. The stimuli
consisted of two sets of spatially intermingled, finite-life random dots
that moved across each other. The distance between the dots moving in
different directions was manipulated by spatially pairing the dot
trajectories with various precisions. Data from Experiment 1 indicated
that motion repulsion occurred reliably only when the average distance
between orthogonally moving elements was at least 21.0 arc min. When the
dots were precisely paired, a single global direction intermediate to the
two actual directions was perceived. This result suggests that, at a
relatively small spatial scale, interaction between different directions
favors motion attraction or coherence, while interaction at a somewhat
larger scale generates motion repulsion. Similarly, data from Experiment 2
indicated that binocular motion rivalry was significantly diminished by
spatially pairing the dots, which moved in opposite directions in the two
eyes. This supports the recent proposal that rivalry occurs at or after
the stage of binocular convergence, since monocular cells could not have
directly responded to our interocular pairing manipulation. Together,
these findings suggest that the neural mechanisms underlying motion
perception are highly sensitive to the fine spatial relationship between
moving elements.
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