Direction perception in complex dynamic displays: the integration of direction information.
We created random-dot cinematograms in which each dot's successive movements were independently drawn from a Gaussian distribution of directions of some characteristic bandwidth. Such a display, comprising many different, spatially intermingled local motion vectors, can produce a percept of global coherent motion in a single direction. Using pairs of cinematograms, direction discrimination of global motion was measured under various conditions of direction distribution bandwidth, exposure duration, and constancy of each dot's path. A line-element model gave an excellent account of the results: (i) over a considerable range, discrimination was unaffected by the cinematogram's direction distribution bandwidth; (ii) only for the briefest presentations did changes in duration have an effect; (iii) so long as the overall directional content of the cinematogram remained unchanged, the constancy or randomness of individual dots' paths did not affect discrimination. Finally, the line-element model continued to give a good account of the results when we made additional measurements with uniform rather than Gaussian distributions of directions.
Department of Psychology, Northwestern University, Evanston, IL 60208.
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Watamaniuk
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Sekuler
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Williams
D004192:Discrimination, Psychological / Q000502:physiology; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D008433:Mathematics; D008959:Models, Neurological; D009039:Motion Perception / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology*; D012684:Sensory Thresholds / Q000502:physiology