# Stochastic Properties of Segmentation-Rivalry Alternations.

K. F. Arrington

* Perception, * 1996; 25, * Suppl. * p. 62.

European Conference on Visual Perception (ECVP),

Strasbourg, France, 9-13th September 1996.

## Abstract.

Segmentation rivalry is the alternation of perceived depth that occurswhen depth information from, e.g. occlusion and stereo disparity cues,are inconsistent (Arrington & Held, 1995, Arvo Abstracts). It wasconjectured that the rivalry is based on reciprocal inhibition betweenend-stopped cell populations that code the same spatial location butopposite direction of surface segmentation in depth. Here thestochastic properties of these depth alternations are analyzed andcompared to prior analysis (Blake, Fox, McIntyre, 1971, J. Exp. Psych.88:3) of binocular rivalry alternations, which have suggested thatsuccessive phase durations are approximated by a theoretical gammadistribution: f(x)=b^a/Exp[LogGamma(a)]*x^(a-1)*Exp[-b*x]. Phenomenallyin-front (F) vs. phenomenally behind (B) phase durations duringsegmentation rivalry were collected at 2' stereo disparity thatproduces a maximal alternation rate and approx. 50% duty cycle. Leastsquare error fit to the two duration data sets was very good (F:a=3.69, b=0.514; B: a=6.54, b=0.780) and the chi-square goodness-of-fitshowed insignificant (p .LE. 0.01) departures from the theoretical gammadistribution when the histogram was smoothed and in some cases whennot smoothed.

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