August 2010
Volume 10, Issue 7
Vision Sciences Society Annual Meeting Abstract  |   August 2010
Perceptual grouping of ambiguous motion
Author Affiliations
  • Stuart Anstis
    Dept of Psychology, UC San Diego
Journal of Vision August 2010, Vol.10, 848. doi:
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      Stuart Anstis; Perceptual grouping of ambiguous motion. Journal of Vision 2010;10(7):848.

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      © ARVO (1962-2015); The Authors (2016-present)

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Introduction. What are the rules of common fate? How are spots that move in different directions grouped perceptually? Method. A pair of spots, separated by 2°, rotate about their common centre at 1 rps. Four such pairs spin in synchrony at the corners of an imaginary square of side 8°. Results. On first viewing, observers report four spinning pairs (Local motion), but after 5–20s the percept suddenly changes to two overlapping 8° squares circling around (Global motion). Thereafter, global motion tends to predominate. Factors that increase local motion include: Gazing straight at a spinner. Proximity – putting the two spots in a spinner closer together. Orientation – replacing the spots within a spinner by two radial or tangential dashes (as if painted on an invisible disk). Luminance – making each spot-pair a different grey. Increasing the number of spots in each spinner from 2 up to 3 or 4. Factors that increase global motion include: Viewing spinners in peripheral vision. Moving the two spots in a spinner further apart. Orientation – replacing the spots with two floating lines that remain horizontal (or vertical) as they spin. Luminance polarity – on a grey surround, four spots defining an 8° square (one spot from each pair) are black, the remaining spots are white. Increasing the number of spinners from 4 to 8. Conclusions. It is a more parsimonious perceptual hypothesis to group the data from the motion array into only two objects (squares) moving globally, rather than into four objects (spinners) moving locally.

Anstis, S. (2010). Perceptual grouping of ambiguous motion [Abstract]. Journal of Vision, 10(7):848, 848a,, doi:10.1167/10.7.848. [CrossRef]
 UCSD Senate.

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