The influence of encoding intention on electrophysiological indices of recognition memory.

The main aim of this study was to further specify the encoding and retrieval conditions that determine the success of an ERP-based memory assessment procedure, originally derived from lie detection studies. We examined whether event-related brain potentials (ERPs) recorded during successful and unsuccessful retrieval would vary according to intentional (study) and incidental (repetition) encoding conditions. Participants (N=20) were asked to indicate recognition of previously studied words (learned targets, p=0.2) and words that were used as distractors in a preceding recognition task (repeated targets, p=0.2). Words that were recognised elicited a P3 component, which was largely absent for new words and words that failed to be recognised. Encoding intention was found to increase the P3 amplitude slightly but had no influence on P3 scalp distribution, suggesting that the differently encoded targets were similarly processed during retrieval but to a different extent. The amplitude difference was explained in terms of variance in memory trace strength and decision confidence. With respect to negative findings for repeated items in our earlier study (Van Hooff, J.C., Golden, S. 2002. Validation of an event-related potential memory assessment procedure: Intentional learning as opposed to simple repetition. J. Psychophysiol., 16, 12-22.), it was suggested that the instruction to actively retrieve the repeated words was essential for obtaining reliable indications of the presence or absence of weak memory traces.