Event-related potential indices of masked repetition priming

Two experiments sought to identify event-related potential (ERP) correlates of masked repetition priming of words in lists and to verify that such effects are not due to brief prime durations. In Experiment 1, prime stimuli were masked and their durations were individually titrated for each participant. Targets that were immediate or delayed repetitions of masked primes resulted in attenuation of the N400, with little or no enhancement of a late positive component (LPC). Delayed, in-the-clear repetitions of unmasked targets led to attenuation of the N400 and enhancement of the LPC. Experiment 2 used similar stimulus timing parameters, but primes were unmasked. More typical unmasked repetition effects were observed for immediate repetitions including a larger attenuation of the N400 and enhancement of the LPC. These findings are discussed within current notions of the functional significance of the N400 and LPC. Descriptors: ERPs, Repetition, Masked priming, N400, LPC Psychologists have long known that the context in which information occurs plays an important role in how it is processed. Numerous studies have shown that even a single contextual clue or ‘‘prime’ ’ can influence the speed and efficiency of subsequent ‘‘target’ ’ processing, as is the case when prime and target items are semantically related words (e.g., doctorFNURSE) or when the prime and target are repetitions of the same word (e.g., nurseFNURSE). Such priming effects have played an impor-tant role in theories that attempt to explain the structure and function of memory and language processing systems (e.g.