Repetition effects in a lexical decision task: the role of episodic memory in the performance of alcoholic Korsakoff patients.

To examine the contribution of episodic memory to the successful verbal priming performance of Korsakoff patients, we adapted a lexical decision task which holds constant the processing demands during study and testing. Words and nonwords were repeated at a lag of 0, 1, 3, 8 and 15 items and the decrease in response latency was taken as a measure of priming. In Experiment 1, Korsakoff patients showed repetition priming of a magnitude similar to that obtained by alcoholic controls, even at a lag of 15 intervening items. Experiment 2 explored the effect of word frequency on repetition priming. Korsakoff patients again showed normal priming up to lags of 15, and, as expected, these repetition effects were larger for low frequency than for high frequency words. This outcome was felt to be more consistent with an episodically based familiarity account than with a semantic activation account. Finally, Korsakoff patients were found to be impaired in their ability to use episodic memory in an explicit memory task that used the same material under comparable presentation conditions (Experiment 3). Contemporary processing models of episodic memory are discussed as possible explanations for the successful implicit memory performance by amnesic patients on this task.