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Marjan Persuh, Tony Ro; Illusory brightness priming occurs without awareness. Journal of Vision 2009;9(8):351. doi: https://doi.org/10.1167/9.8.351.
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© ARVO (1962-2015); The Authors (2016-present)
Our visual systems are usually confronted with large quantities of information, but due to processing constraints, only a small subset of this information enters awareness. Thus, one issue of fundamental importance in vision is whether conscious and unconscious visual representations differ. The current experiments assessed whether real and illusory brightness processing can proceed in the absence of visual awareness by measuring unconscious priming with metacontrast masking. To assess whether real brightness processing occurs without awareness, a dark or bright priming disk was presented on a neutral gray background and then masked by a dark or bright annulus. In the illusory brightness conditions, a neutral gray priming disk was presented on either a dark or bright background to induce an illusory brightness of the disk via simultaneous brightness contrast. Using a disk to mask stimulus onset asynchrony that resulted in approximately equal numbers of aware and unaware trials, we found that reaction times to the brightness of the masks were significantly faster when the disk and annulus were identical in luminance than when the disk was bright (or dark) and the mask was dark (or bright), for both the aware and unaware trials. When the neutral gray disk was presented on a dark (or bright) background, such that the gray disk could be consciously perceived as bright (or dark), reaction times were significantly faster to the bright (or dark) annulus than to the dark (or bright) annulus. Surprisingly, this illusory brightness priming occurred in both the aware and unaware trials. Additional analyses and a control experiment indicate that these effects cannot be explained by independent effects of the background or adaptation. These results demonstrate that both real and illusory brightness contrast can be represented unconsciously and suggest that simultaneous brightness contrast occurs at very early levels of visual input.
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