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Journal of the Optical Society of America A

Journal of the Optical Society of America A


  • Vol. 16, Iss. 7 — Jul. 1, 1999
  • pp: 1531–1540

Imputation of direction of motion in one dimension

Miguel A. Garcı́a-Pérez and Eli Peli  »View Author Affiliations

JOSA A, Vol. 16, Issue 7, pp. 1531-1540 (1999)

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Under many conditions below the Nyquist limit, a drifting grating briefly displayed on a CRT is consistently perceived as moving in the opposite direction. Taking into account the sample-and-hold operation of CRT’s, we have derived the temporal-frequency spectra of the displayed gratings and found that they have a broad range of components moving in either direction. We have measured the perceived direction of motion of over 150 different short-duration stimuli, and we have studied the relation that performance bears to narrow-band power imbalance—the normalized difference between power in the positive- and negative-frequency half-lines within a specific band. Perceived direction of motion is highly related to power imbalance in 1-Hz-wide bands centered between 10 and 15 Hz, but none of these bands alone can account for more than 84–91% of the variance of the data, and each band ostensibly fails to explain data from a subset of the stimuli. When broadband power imbalance is determined by weighting the spectrum with an inverted-U-shaped function peaking at ∼12 Hz, the explained variance increases to 91–97%. Our results suggest that the imputation of direction of motion to stimuli with complex spectra is based on broadband power imbalance determined after weighting the temporal-frequency spectrum with an inverted-U-shaped function.

© 1999 Optical Society of America

OCIS Codes
(330.0330) Vision, color, and visual optics : Vision, color, and visual optics
(330.5510) Vision, color, and visual optics : Psychophysics
(330.7310) Vision, color, and visual optics : Vision

Original Manuscript: October 29, 1998
Revised Manuscript: February 16, 1999
Manuscript Accepted: February 16, 1999
Published: July 1, 1999

Miguel A. Garcı́a-Pérez and Eli Peli, "Imputation of direction of motion in one dimension," J. Opt. Soc. Am. A 16, 1531-1540 (1999)

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  11. Recall, however, that only 16 of the 19 conditions were actually different, since one of them (constant-contrast three-frame presentations) was replicated twice and another (constant-contrast two-frame presentations) was replicated once.
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  13. The inherent variability in the data should be taken into account for this judgment. Data from our conditions with flickering stimuli give an estimate of this variability, and these data can easily be seen in the panels of Fig. 8(c) as a string of vertically aligned points at an abscissa of 0 and around an ordinate of 50. The vertical spread of these strings gives an indication of the response variability that one has to put up with in these plots.
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