June 2004
Volume 4, Issue 8
Free
Vision Sciences Society Annual Meeting Abstract  |   August 2004
The perceived visual direction of monocular objects in random-dot stereograms is influenced by horizontal but not vertical disparity
Author Affiliations
  • Srividhya Hariharan
    University of Houston, USA
  • Harold E. Bedell
    College of Optometry and Center for Neuro-engineering & Cognitive Science, University of Houston, USA
Journal of Vision August 2004, Vol.4, 588. doi:10.1167/4.8.588
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      Srividhya Hariharan, Harold E. Bedell; The perceived visual direction of monocular objects in random-dot stereograms is influenced by horizontal but not vertical disparity. Journal of Vision 2004;4(8):588. doi: 10.1167/4.8.588.

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Abstract

Purpose. The perceived direction of a monocular stimulus that is embedded in a 3-D binocular display is reported to lie between those of nearby binocular targets, a phenomenon referred to as binocular “capture.” The purpose of this study was to evaluate whether stereoscopic depth is necessary for binocular “capture” to occur. Methods. Observers with normal stereopsis (N=4) viewed a pair of 1 by 2 deg random-dot (RD) rectangles, separated either vertically or horizontally by 40 min arc. The upper or lefthand rectangle was in the same plane as a central fixation cross and the lower or righthand rectangle was presented with horizontal (range: +/− 16 min arc) or vertical (range: +/− 12 min arc) disparity. As expected, observers perceived only the rectangles with horizontal disparity in depth. On each trial, observers judged the relative horizontal or vertical position of two 6 by 30 min-arc lines, one superimposed on each rectangle, that were flashed for 100 ms to either the left or right eye. Results. Perceived horizontal alignment between the two monocular lines changes systematically (up to ca. 5 min arc) with the magnitude and direction of horizontal disparity. The change in perceived alignment varies idiosyncratically by observer and eye, but remains less than half the horizontal stimulus disparity. In contrast, perceived vertical alignment between the monocular lines does not change with the vertical stimulus disparity. Conclusions. If the perceived direction of a monocular visual target depends on the directions of neighboring binocular targets, then the perceived alignment between monocular lines in a stereogram should vary similarly with horizontal and vertical disparity. Our results show that the perceived alignment varies systematically with horizontal but not with vertical disparity of the stereogram, indicating that depth perception rather than allelotropia is a necessary condition for binocular “capture.”

Hariharan, S., Bedell, H. E.(2004). The perceived visual direction of monocular objects in random-dot stereograms is influenced by horizontal but not vertical disparity [Abstract]. Journal of Vision, 4( 8): 588, 588a, http://journalofvision.org/4/8/588/, doi:10.1167/4.8.588. [CrossRef]
Footnotes
 Support: R01 EY05068
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