LETTER-POSITION CODING IN RANDOM CONSONANT ARRAYS

The processing of letter-position information in randomly arranged con sonant strings was investigated using a masked prime variant of the al phabetic decision (letter/nonletter classification) task. In Experimen t 1, primes were uppercase consonant trigrams (e.g., FMH) and targets were two uppercase Xs accompanied by the target letter or a nonletter (e.g., XMX, X%X). Response times were systematically faster when targe t letters were present in the prime string than when target letters we re not present in the prime string. These constituent letter-priming e ffects were significantly stronger when the target letter appeared in the same position in the prime and target stimuli. This contrast betwe en position-specific and position-independent priming was accentuated when subjects responded only when all the characters in the target str ing were letters (multiple alphabetic decision) in Experiments 2 and 3 . in Experiment 4, when prime exposure duration was varied, it was fou nd that position-specific priming develops earlier than position-indep endent priming. Finally, Experiment 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 i n an interactive-activation framework.