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Speed and direction of locally-paired dot patterns
1Visual Development Unit, Department of Psychology, University College London, Gower Street, WC1E 6BT, London, UK. w.curran@ucl.ac.uk
Vision Research
|July 6, 2000
Summary
Perception of motion transparency is lost with locally-balanced random-dot displays. However, human subjects still perceive coherent motion, judging it as a vector average of component directions and speeds.
Area of Science:
- Visual perception
- Neuroscience
- Motion perception
Background:
- Transparency in random-dot kinematograms is lost when motion directions are locally balanced.
- Previous research suggests local inhibition between motion detectors causes this phenomenon.
Purpose of the Study:
- Investigate perceived motion in locally-paired random-dot displays.
- Determine how humans judge direction and speed with superimposed, locally-balanced motions.
Main Methods:
- Subjects judged direction and speed of locally-paired stimuli with component directions 60, 90, or 120 degrees apart.
- Stimuli included variations in dot lifetime and component velocities.
Main Results:
- Subjects perceived coherent motion and made reliable direction judgments.
- Judged motion direction and speed followed a vector-averaging rule for all tested conditions.
- This vector-averaging held true even when component dots differed in velocity or speed.
Conclusions:
- The abolition of transparency does not eliminate global motion perception.
- Local interactions abolishing transparency generate a vector combination, not solely inhibition.
- Perceived motion in these displays is a vector average of component motions.