The ERP late positivity: a graduated response to stimulus repetition

The late positive component of the event-related potential (ERP) is sensitive to stimulus repetition but evidence to date is ambiguous regarding whether it is differentially sensitivity to multiple repetitions, ERPs were monitored in a running recognition paradigm while participants indicated whether a series of test words had been presented earlier. In study 1, some words were repeated up to three times, at lags of 15, 30 and 45. In study 2, words were repeated only once but interstimulus intervals were varied. As expected, the late positivity was sensitive to previous occurrence and although it did not vary reliably in response to the size of interstimulus interval, it did provide a reliable graded reflection of the number of stimulus repetitions.