Visual Processing of Object Velocity and Acceleration
Annual technical rept. 16 Jan 1993-15 Jan 1994
SMITH-KETTLEWELL EYE RESEARCH INST SAN FRANCISCO CA
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Human observers can easily detect a signal dot moving, in apparent motion, on a trajectory embedded in a background of random-direction motion noise. A high detection rate is possible even though the spatial and temporal characteristicsstep size and frame rate of the signal are identical to the noise, making the signal indistinguishable from the noise on the basis of a single pair of frames. The success rate for detecting the signal dot was as high as 90 when the probability of mismatch from frame-to-frame, based on nearest neighbor matching was 0.3 control experiments showed that trajectory detection is not based on detecting a string of collinear dots, i.e., a stationary position cue. Nor is a trajectory detected because produces stronger signals in independent local motion detectors. For one thing, trajectory detection improves with increases in duration, up to 250 - 400 msec, a duration longer than the integration typically associated with a single motion detector. Moreover, the signal dot need not travel in a straight line to be detectable. The signal dot was as reliably detected when it changed its direction a small amount 30 deg each frame. Consistent with this, circular paths of sufficiently low curvature were as detectable as straight trajectories.
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