# Cognitive Penetrability and Perceptual Justification **Opening (not a real abstract):** Cognitive Penetrability and Perceptual Justification* Susanna Siegel * Harvard University Forthcoming in Nous, 2011. It is sometimes said that in depression, everything looks grey.1 If this is true, then mood can influence the character of perceptual experience: depending only on whether a viewer is depressed or not, how a scene looks to that viewer can differ even if all other conditions stay the same. This would be an example of cognitive penetration of visual experience by another mental state. Here the influential cognitive state is a mood. Other putative examples of cognitive penetrability involve beliefs: to the reader of Russian, the sheet of Cyrillic script looks different than it looked to her before she could read it. When you know that bananas are yellow, this knowledge affects what color you see bananas to be (an achromatic banana will appear