Benefits of Immediate Repetition Versus Long Study Presentation on Memory in Amnesia

Objective: This study aimed to resolve discrepant findings in the literature regarding the effects of massed repetition and a single long study presentation on memory in amnesia. Method: Experiment 1 assessed recognition memory in 9 amnesic patients and 18 controls following presentation of a study list that contained items shown for a single short study presentation, a single long study presentation, and three massed repetitions. In Experiment 2, the same encoding conditions were presented in a blocked rather than intermixed format to all participants from Experiment 1. Results: In Experiment 1, control participants showed benefits associated with both types of extended exposure, and massed repetition was more beneficial than long study presentation, F(2, 34) = 14.03, p < .001, partial η² = .45. In contrast, amnesic participants failed to show benefits of either type of extended exposure, F < 1. In Experiment 2, both groups benefited from repetition, but did so in different ways, F(2, 50) = 4.80, p = .012, partial η² = .16. Amnesic patients showed significant and equivalent benefit associated with both types of extended exposure, F(2, 16) = 5.58, p = .015, partial η² = .41, but control participants again benefited more from massed repetition than from long study presentation, F(2, 34) = 23.74, p < .001, partial η² = .58. Conclusions: The findings suggest that previous inconsistencies in the literature were due to procedural differences across studies. We discuss group differences in terms of the mechanisms by which both forms of extended exposure facilitate performance in each group.