Abstract

The aim of the present experiments was to investigate the maximum displacement over which coherent motion can be perceived (D_max) for a stroboscopically illuminated moving random-dot pattern, both as a function of the size of the pattern and as a function of the spatial-frequency content. Perception of coherent motion was defined operationally as the ability to discriminate opposite directions. The maximum velocity (V_max) for which the observer could discriminate the direction of motion for a given strobe rate was obtained by using a forced-choice staircase procedure. V_max was measured as a function of the strobe rate for four different sizes of the pattern. For each pattern size V_max was limited by the spatial asynchrony between the flashes (D_max). For a given size of the pattern, D_max did not depend on the temporal asynchronies tested (10–100 msec). D_max values were increased with the size of the pattern. Bandpass rectangular filtering was used to change the spatial-frequency content of the pattern. There was a gradual increase in D_max as the spatial-frequency content shifted to low spatial frequencies. Interestingly, the D_max that was obtained with the unfiltered pattern was larger than that obtained with the high-pass pattern but also smaller than that obtained with the low-pass pattern. The present results are in agreement with results obtained with a two-frame display. D_max is not a fixed value: it depends on the size of the pattern as well on the spatial-frequency content. Larger D_max values are probably mediated by bilocal motion detectors with larger receptive fields, which are recruited either by increasing the pattern size (given that the duration of the motion is long enough) or by lowering the spatial frequency of the stimulus. The results obtained with the unfiltered random-dot pattern indicate that detectors tuned to high spatial frequencies inhibit detectors tuned to low spatial frequencies.

© 1989 Optical Society of America

Motion interference in speed discrimination

Samuel F. Bowne, Suzanne P. McKee, and Donald A. Glaser
J. Opt. Soc. Am. A 6(7) 1112-1121 (1989)

Influence of contrast on foveal and peripheral detection of coherent motion in moving random-dot patterns

W. A. van de Grind, J. J. Koenderink, and A. J. van Doorn
J. Opt. Soc. Am. A 4(8) 1643-1652 (1987)

Discontinuity limits for the generation of visual motion aftereffects with sine- and square-wave gratings

Kathleen Turano and Allan Pantle
J. Opt. Soc. Am. A 2(2) 260-266 (1985)

What determines the maximum displacement limit for spatially broadband kinematograms?

Richard A. Eagle
J. Opt. Soc. Am. A 13(3) 408-418 (1996)

Sequential recruitment in the discrimination of velocity

Suzanne P. McKee and Leslie Welch
J. Opt. Soc. Am. A 2(2) 243-251 (1985)