The effects of prime visibility on ERP measures of masked priming.

In two experiments, the effect of the duration (40, 80 and 120 ms) of pattern masked prime words on subsequent target word processing was measured using event-related potentials. In Experiment 1, target words were either repetitions of the prior masked prime (car-CAR) or were another unrelated word (job-CAR). In Experiment 2, primes and targets were either semantically related (cap-HAT) or were unrelated (car-HAT). Unrelated target words produced larger N400s than did repeated (Exp 1) or semantically related (Exp 2) words across the different prime durations and these N400 priming effects tended to be smaller overall for semantic than repetition priming. Moreover, there was only a modest decline in the size of N400 repetition priming at the shortest prime durations, and there was no relationship between this N400 effect and a measure of prime categorization performance. However, the size of semantic priming at the shortest durations was relatively smaller than at longer durations and was correlated with prime categorization performance. The findings are discussed in the context of the functional significance of the N400 as well as a model that argues for different mechanisms during masked repetition and semantic priming.