November 2002
Volume 2, Issue 7
Free
Vision Sciences Society Annual Meeting Abstract  |   November 2002
Relative motion, not polarity, breaks ‘surface tension’
Author Affiliations
  • Erik Blaser
    Rutgers University, USA
Journal of Vision November 2002, Vol.2, 92. doi:10.1167/2.7.92
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      Erik Blaser, Zoltan Vidnyanszky, Thomas Papathomas; Relative motion, not polarity, breaks ‘surface tension’. Journal of Vision 2002;2(7):92. doi: 10.1167/2.7.92.

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Abstract

Purpose. To investigate the rules that underlie visual surface integration and segmentation. Methods. Observers viewed motion transparency: two fields of superimposed, drifting dots. One field (of black dots) drifted rightward, the other (white dots) leftward. This stimulus was used as the adaptor in a motion aftereffect (MAE) paradigm. Results 1. When tested with a static field of black and white dots, no MAE was reported; i.e. the expected polarity-contingent MAE was not expressed. Any polarity-contingent MAE would have to have shown up as a transparent MAE (that is, with the black dots in the test field undergoing illusory motion to the left simultaneously with the superimposed white dots undergoing illusory rightward motion); such effects are notoriously difficult to produce (because, we hypothesize, such a stimulus is treated as a single surface, which is assigned a single direction of motion). However, we reasoned that if we facilitated the segmentation of the black and white surfaces during testing, the MAE could be expressed. Results 2. Using the same adaptor described above, we then introduced a relative motion cue into the test (white dots moving upward, black downward). Now any horizontal polarity-contingent MAE would be added to these vertical motion vectors, producing a, in this case, clockwise deflection of the perceived shear axis. Four observers perceived tilts of 4–8 deg. Conclusions. Polarity alone was not sufficient for segmentation of the two surfaces (a likely necessary condition if each are to move in different directions), and hence the polarity-contingent MAE was either actively suppressed, or too weak to break this ‘surface tension’. Only when a powerful relative motion segmentation cue was added was the surface tension broken, and the polarity-contingent MAE expressed. Ongoing studies are quantifying the contribution and interaction of such surface segmentation cues.

Blaser, E., Vidnyanszky, Z., Papathomas, T.(2002). Relative motion, not polarity, breaks ‘surface tension’ [Abstract]. Journal of Vision, 2( 7): 92, 92a, http://journalofvision.org/2/7/92/, doi:10.1167/2.7.92. [CrossRef]
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