Pii: S0364-0213(01)00042-8

Fodor has argued that observation is theory neutral, since the perceptual systems are modular, that is, they are domain-specific, encapsulated, mandatory, fast, hard-wired in the organism, and have a fixed neural architecture. Churchland attacks the theoretical neutrality of observation on the grounds that (a) the abundant top-down pathways in the brain suggest the cognitive penetration of perception and (b) perceptual learning can change in the wiring of the perceptual systems. In this paper I introduce a distinction between sensation, perception, and observation and I argue that although Churchland is right that observation involves top-down processes, there is also a substantial amount of information in perception which is theory-neutral. I argue that perceptual learning does not threaten the cognitive impenetrability of perception, and that the neuropsychological research does not provide evidence in favor of the top-down character of perception. Finally, I discuss the possibility of an off-line cognitive penetrability of perception. © 2001 Cognitive Science Society, Inc. All rights reserved.