Abstract
Previously, we reported that a convex region is more likely to be seen as figure when surrounded by other convex regions (Kim & Peterson, 2001; 2002; Peterson & Kim, 2001). For instance, for briefly exposed black and white displays of alternating concave and convex regions d' increases from 0.36 to 1.04 to 2.07 as the number of fully convex regions increases from 1.0 to 1.5 to 3.5. We investigated whether similar ‘context effects” were obtained for mirror symmetry. In Experiment 1, observers viewed black and white displays composed of alternating symmetric and asymmetric regions and reported whether they perceived black or white regions as figure (lightness was not confounded with cue). Symmetric regions were seen as figure on approximately 59% of the trials, regardless of whether there were 1, 2, or 3 symmetric regions in the display. In Experiment 2, observers reported whether a probe shown on one of the regions on either side of fixation appeared to lie “on” or “off” the perceived figure. Sensitivity to symmetry as a configural cue (d' = 0.17) did not vary with the number of symmetric regions. In Experiment 3, using the probe task we found that a single symmetric region in an alternating black and white display was more likely to be seen as figure when the other region of the same lightness was convex (d' = 1.02) versus symmetric (d' = 0.17) or asymmetric (d' = 0.17). We consider which mechanisms underlie the within cue and cross cue context effects. Support: National Science Foundation (BCS 9906063)
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