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Jennifer E. Anderson, Michael W. Levine, J. Jason McAnany; Why might black tetragons be more effective than white for inducing blanking?. Journal of Vision 2013;13(9):1148. doi: 10.1167/13.9.1148.
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A regular 2D array of four-sided figures (tetragons) placed on a neutral gray background forms a grid of alleys and intersections. Illusory smudges or scintillations can appear within the intersections (Hermann and Scintillating Grid, respectively). This pattern also increases thresholds for detection of targets placed within the intersections. Targets of the same polarity as the tetragons are only somewhat "obscured" by the tetragons. But if the targets and tetragons are of opposite polarity, the targets undergo a strong "blanking" effect (Extinction Illusion or Vanishing Disk). Curving the alleys increases tetragon complexity, and target detection becomes even more difficult. Overall, complex tetragons further obscure any targets, but only the effect of blanking is orientation dependent. Blanking is strongest when target and tetragons share similar orientations. Although obscuring occurs regardless of target and tetragon polarity, the blanking effect is weaker for white tetragons than for black tetragons. We test two possible reasons for this difference: (1) The contrast difference between alleys and tetragons might play a role in overall target detection; previous work did not account for the luminance of the alley gray. We changed alley grays covering a range of contrasts – yet black tetragons were always more effective than white at the same alley gray. (2) Superimposing white tetragons on an otherwise neutral-gray field creates a sharp increase in overall luminance between the display and response screen; superimposing black tetragons decreases luminance. We tested whether change in overall luminance was the important factor. To mitigate this abrupt temporal change, we made the luminance of the inter-trial response screen equal to the overall luminance of the test display. We found that change in luminance does not contribute to the weaker blanking effect of white tetragons. These results suggest that the effect may depend upon the asymmetry of ON and OFF systems.
Meeting abstract presented at VSS 2013
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