Different attentional resources modulate the gain mechanisms for color and luminance contrast

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We used an interference paradigm to investigate whether attention is attribute-specific at early levels of visual processing. We show that the peripheral increment thresholds for luminance contrast deteriorate when the observer is currently performing another luminance (form or contrast) discrimination task in central view, but not when he or she is performing a color discrimination task. Similar results were obtained for color increment thresholds, indicating that the interference is specific to contrast modality. The effects are strong and robust over primary task difficulties and perceptual learning levels. Modeling suggests that attention improves contrast sensitivity by modulating the gain of the neuronal response to contrast. These results suggest that attention is parceled in independent resources for luminance and color contrast.