June 2006
Volume 6, Issue 6
Free
Vision Sciences Society Annual Meeting Abstract  |   June 2006
Motion strength is not what is summed in the vector summation computation of plaid motion
Author Affiliations
  • Danting Liu
    Department of Cognitive Sciences, University of California, Irvine
  • George Sperling
    Department of Cognitive Sciences, University of California, Irvine
Journal of Vision June 2006, Vol.6, 1046. doi:10.1167/6.6.1046
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      Danting Liu, George Sperling; Motion strength is not what is summed in the vector summation computation of plaid motion. Journal of Vision 2006;6(6):1046. doi: 10.1167/6.6.1046.

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Abstract

First-order motion is assumed to be detected by “motion energy” or equivalently “Reichardt Detectors.” The output of such detectors is “motion strength”, a quantity that is proportional to the square of the contrast of a moving sinewave grating. When two sine gratings of possibly different contrasts and orientations move together (a plaid), do the component motion strength vectors sum to determine perceived direction of the plaid? To investigate this question, we did a series of experiments using two component gratings with various spatiotemporal frequencies, different angles between component gratings, different durations of presentation, and a wide range of contrasts for the component gratings. In plaid sinewave stimuli in which the contrasts of the components differed by less than a factor of about 4, the two components contributed equally to the combined motion. When the contrast of one component grating exceeded the other by more than 4, it masked the motion of the lower-contrast grating and only the larger component contributed to the combined motion. The results indicate that motion-strength vectors are not what is summed in plaid motion perception.

Liu, D. Sperling, G. (2006). Motion strength is not what is summed in the vector summation computation of plaid motion [Abstract]. Journal of Vision, 6(6):1046, 1046a, http://journalofvision.org/6/6/1046/, doi:10.1167/6.6.1046. [CrossRef]
Footnotes
 Air Force Office of Scientific Research, Life Sciences, Grant FA9550-04-1-0225
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