The Perception of the Higher Derivatives of Visual Motion.
Final rept. 30 Sep 85-1 Oct 86,
NEW YORK UNIV N Y DEPT OF PSYCHOLOGY
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This final report provides a brief overview of work conducted prior to the final hear of this project, as more complete descriptions have been published. The overview covers work done on the sensitivity of the perceptual system to changing speed. The stimuli were sinusoidal gratings drifting normal to the lengths of their bars, and speed was modulated. Threshold modulation of speed was about 12 of average speed, although performance was better for higher spatial frequencies and higher average speeds. To avoid effects of contour change,we adopted a random dot approach in which threshold for motion of dots was determined as a function of the proportion of dots exhibiting correlated motion. Thus, threshold is expressed as a signal to noise ratio. For the detection of uniform motion of moderate speed, the percent correlation was about 5.7, i.e., 5 or 6 dots out of 100 had to move together, with all the other dots in random motion. There was approximately a 47 increase in threshold for change in direction of motion where the change in direction was about 30 deg. However, in a parametric experiment it was found that there was a monotonic decrease in threshold with amount of change in direction. Where the change in direction was only 2 deg, it could not be detected even with 100 correlation. At 3 deg. 96 correlation was required. Only 14 correlation required at 30 deg.
- Anatomy and Physiology