Perceptual versus postperceptual mediation of visual context effects: evidence from the letter-superiority effect.

Two experiments demonstrated letter-context effects that cannot easily be accounted for by postperceptual theories based on structural redundancy, figural goodness, or memory advantage. In Experiment 1, subjects identified the color of a letter fragment more accurately in letter than in nonletter contexts. In Experiment 2, subjects identified the feature presented in a precued color more accurately in letters than in nonletters. We argue that these effects result from top-down perceptual processing.