Knowledge within perception: masking caused by incompatible interpretation.

Abstract Most people and some scientists assume that knowledge does not affect the perceptual representation of a pattern but merely may change its evaluation afterwards. An experiment was set up to show that the perceptual representation itself depends on an interaction with immediate context information, even in the case of clearly unambiguous patterns. In each trial two patterns were presented successively for 10 msec on the same place with an onset asynchrony between 10 and 70 msec. Presented in one order, the perceptual representation of the first pattern was predicted to be able to reinforce a latent interpretation of the second one. For the same patterns presented in the reversed order, however, no such interaction was predicted. Subjects had to identify one of the two patterns of a pair. The number of correct identifications differed for the two opposed orders of presentation as predicted. The effect was present with stimulus onset asynchronies as short as 30 msec. This gives an indication of the rate at which pattern interpretations can be developed.