PRIMING AND RESPONSE SELECTION PROCESSES IN LETTER CLASSIFICATION AND IDENTIFICATION TASKS

The processing of isolated visual letters was studied by means of a priming paradigm. In alphabetic (letter vs. nonletter) classification, any letter prime reduced response times to letter targets. Additional facilitation occurred only with primes physically identical to the target. In letter naming, facilitation was seen with primes nominally identical to the target even when they were physically different. This result is not due to phonological priming because phonologically similar primes had no effect on naming times. Primes nominally different from the target but physically similar to it increased naming times. The classification task seems to be performed through the global monitoring of stored visual knowledge of letters. In contrast, the absolute identification of letters appears to rest on a signal-to-noise statistic derived from an abstract encoding of letter identities. Connectionist simulations provide support for these proposals.