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Luke Huszar, Antoine Barbot, Marisa Carrasco; Linking the effects of exogenous attention on contrast sensitivity and on apparent contrast. Journal of Vision 2020;20(11):1159. doi: https://doi.org/10.1167/jov.20.11.1159.
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© ARVO (1962-2015); The Authors (2016-present)
Attention modulates visual appearance (review, Carrasco & Barbot, 2019), playing a fundamental role in our subjective impression of the visual world. However, research has predominantly focused on how attention alters visual sensitivity. Here, we investigated whether attentional effects on contrast sensitivity and appearance share a common cause. We concurrently measured the effects of exogenous attention on contrast sensitivity and apparent contrast, and used psychophysical reverse correlation and computational modeling to link these effects.
Observers reported which of two Gabor patches was of higher contrast. One stimulus had fixed contrast ('standard', 40%), while the other varied ('test', 7-100%). Stimuli were embedded in noise that randomly varied across trials. Exogenous attention was manipulated using pre-cues briefly flashed above one (Cued condition) or both stimuli (Neutral condition). To measure the effect of attention on appearance, we estimated the point-of-subjective equality (PSE) between conditions. For reverse correlation, trial-to-trial fluctuations in stimulus energy were correlated with behavioral judgments to assess how sensitivity to orientation and spatial frequency content influenced apparent contrast. Contrast sensitivity kernels for each condition were fit with 2D Gaussians to evaluate whether and how attention changed the amplitude, tuning width, and/or baseline of these sensitivity profiles.
Exogenous attention increased apparent contrast: the Cued PSE differed from the point of objective equality (40% contrast), while the Neutral PSE matched it. Reverse correlation revealed higher sensitivity for Cued than Neutral, with Gaussian fits to both individual observers and the mean capturing this difference as a change in multiplicative gain. Model simulations evaluated the extent to which different perceptual and attentional gain control mechanisms could account for the results.
Our findings link the effects of attention on perceptual sensitivity and appearance by showing how changes in sensitivity manifest as differences in subjective appearance.
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