Recognition memory in amnesic patients: A defect of acquisition?

Abstract

Comparative performance of Korsakoff patients and controls on picture recognition tests was investigated by manipulating two acquisition variables: stimulus exposure duration and frequency of item presentation. Subjects were tested under each of 9 conditions of presentation, corresponding to the orthogonal combination of 3 stimulus exposure durations (0·5, 1 and 2 sec) and 3 frequencies of presentation (1,2 and 4 exposures). Yes-no recognition was tested 20 min after each presentation series. The main findings were: (1) in both groups, recognition was a function of total stimulus exposure time, i.e. the product of duration and frequency of presentation; (2) when total exposure time was the same as or double the control value, recognition performance of Korsakoff patients was significantly worse than that of controls, but when total exposure time was four or more times the control value, recognition performance by Korsakoff patients was as good as that of controls. We infer that in amnesia there is a defect located at the stage where memories are acquired, and that this defect may at least in part be characterised by a reduction in the speed with which information can be processed. It is suggested that alternative explanations of our findings, which postulate a defect of either storage or retrieval, are disconfirmed on other grounds.