Part-list cuing in amnesic patients: Evidence for a retrieval deficit

People showing the amnesic syndrome typically have intact working memory, unimpaired semantic memory, and normal procedural learning, priming, and classical conditioning. The central and most striking feature is difficulty in memory for newly acquired episodic material (Baddeley, 1997). Explanations of the amnesic syndrome using information processing accounts are based on the hypothetical memory stages of encoding, storage, and retrieval and/or their interactions, exploring the possibility of isolating the stage(s) at which the deficit occurs. Such an information processing approach to the problem bears implications for memory theory and can guide physiological research. Current information processing accounts of the amnesic syndrome explain the syndrome mainly in terms of storage deficits and deficits that arise from problems in the encoding–retrieval interaction (for a review see Baddeley, 1997, or Mayes & Dawnes, 1997). Storage deficit proposals assume that amnesic patients show a deficit in the initial consolidation of episodic material into long-term memory. This deficit is assumed to arise mainly in the case of the consolidation of complex associations and less, if at all, in the consolidation of simple associations and information (Isaac & Mayes, 1999a, 1999b). Proposals emphasizing deficits in the encoding–retrieval interaction assume that amnesic patients have trouble encoding the features of material in such a way that cues directed toward feature representation can evoke the desired item directly. This difficulty is supposed to arise particularly for semantic feature representation (Cermak, 1997). Whereas this latter explanation of the amnesic syndrome takes possible problems in retrieval into account, there is greater emphasis on input than output. Indeed, most current explanations of the amnesic syndrome agree insofar as they do not attribute the syndrome to deficits located primarily at the retrieval stage of the recall process. This holds although originally the syndrome was assumed to reflect mainly a retrieval deficit (Warrington & Weiskrantz, 1974). The agreement that retrieval problems do not play a major role in the amnesic syndrome rests mostly on studies that examined whether amnesics are excessively susceptible to interference effects. Neither Warrington and Weiskrantz (1978), investigating retroactive interference, nor Isaac and Mayes (1999a, Experiment 3), investigating proactive interference, found evidence for an interference susceptibility in amnesic patients. At first glance, these results suggest that amnesic patients do not show a retrieval deficit. As the literature on retrieval failures in healthy subjects shows, however, retrieval failures arise not just as a result of retroactive or proactive interference but may be caused by other sources as well. Failures in the retrieval of studied items, for instance, can arise if a subset of the learned items is retrieval practiced before test; such retrieval practice of related items typically impairs rather We thank the two anonymous referees for their comments on an earlier draft of the manuscript. We are also grateful to S. Kiener, C. Lohr, and L. Schiener for their help in collecting the data. Correspondence should be addressed to K.-H. Bäuml, Institut für Psychologie, Universität Regensburg, 93040 Regensburg, Germany (e-mail: karl-heinz. [email protected]). Part-list cuing in amnesic patients: Evidence for a retrieval deficit