Letter position coding in random consonant arrays

The processing of letter-position information in randomly arranged consonant strings was inves- tigated using a masked prime variant of the alphabetic decision (letter/nonletter classification) task. In Experiment 1, primes were uppercase consonant trigrams (e.g., FMH) and targets were two up- percase Xs accompanied by the target letter or a nonletter (e.g., XMX, X%X). Response times were systematically faster when target letters were present in the prime string than when target letters were not present in the prime string. These constituent letter-priming effects were significantly stronger when the target letter appeared in the same position in the prime and target stimuli. This contrast between position-specific and position-independent priming was accentuated when sub- jects responded only when all the characters in the target string were letters (multiple alphabetic decision) in Experiments 2 and 3. In Experiment 4, when prime exposure duration was varied, it was found that position-specific priming develops earlier than position-independent priming. Finally, Ex- periment 5 ruled out a perceptual-matching interpretation of these results. An interpretation is offered in terms of position-specific and position-independent letter-detector units in an interactive- activation framework.