The Perception of the Higher Derivatives of Visual Motion.
Final scientific rept. 1 Jan 82-31 Sep 85,
NEW YORK UNIV N Y
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Sensitivity to changing speed was studied with gratings of various spatial frequencies drifting across a screen while the average velocity was modulated. Thresholds expressed either as the velocity amplitude difference between peak and average velocities or as the maximum acceleration, increased monotonically with average velocity. The threshold for velocity contrast velocity amplitude divided by average velocity actually decreased with average velocity. The velocity contrast was minimal for velocity modulation frequencies of about 2 Hz and for spatial frequencies in the range of 2-4.5 cd. In addition to these basic findings, we failed to find any effect of selective adaptation to changing speed other than that could be attributed to smooth motion. It seems unlikely that mechanisms tuned to respond to changing speed per se are present in the human perceptual system. However, it is not possible to generalize from this to situations where higher derivatives are introduced by causing stimuli to change direction of motion. Author
- Biomedical Instrumentation and Bioengineering