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Michael L. Kramer, Lynn A. Olzak; Collinearity and surround size effects on spatial discrimination tasks. Journal of Vision 2006;6(6):199. doi: 10.1167/6.6.199.
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© ARVO (1962-2015); The Authors (2016-present)
Previous research has shown both collinear facilitation in contrast detection tasks (Solomon & Morgan, Vis. Res., 2000) and a lack of any collinear effects in apparent contrast tasks (Cannon & Fullenkamp, Vis. Res., 1991). The present study was performed to better understand the effect of spatial characteristics of surrounds on suprathreshold spatial discrimination tasks. The tasks used were hyperacuity orientation (centered around vertical) and spatial frequency (centered around 4 cpd) discriminations between 40-minarc, circular center patches of sinusoidal grating. Surrounds were vertical sinusoidal grating rings at exactly 4 cpd, with a ring width of 40-minarc. Surround size and location was modulated using BOW-TIE style stimuli (Cannon & Fullenkamp, Vis. Res., 1991) in order to specifically test how collinearity (or its lack) affects fine spatial discriminations. Discriminability was measured using d' values (obtained from a 6 point response scale). Our preliminary results suggest that collinear surrounds have a stronger inhibitory effect on these discrimination tasks when compared to non-collinear side-flanks of equal size. Our results also suggest that for most people, increasing surround size increases this inhibitory effect.
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