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Accepted: 27 August 2021 / Published online: 28 September 2021
© The Author(s) 2021
Abstract
Here, we present two case studies of extremely long-term retention. In the first, Richard C. Atkinson (RCA) had learned word sequences during experiments for his dissertation. Sixty-seven years later, RCA relearned the same words either in the original order or in a scrambled order. RCA reported no conscious awareness that the words were those used in the dissertation, but his relearning was considerably better for the words in the original order. In the second case study, Denis Cousineau had searched displays of objects for the presence of a target. The targets and foils had been novel at the beginning of training, and his search rate improved markedly over about 70 sessions. After 22 years, retraining showed retention of much of this gain in rate of search, and the rate was markedly faster than search for new objects with the same structure as the trained set. We consider interpretations of these case studies for our understanding of long-term retention.
Keywords Long-term memory . Permastore . Permanence of memory . Skill retention . Memory for skilled search
It is common for memory theorists to distinguish short-term and long-term memories and to assume that the long-term memories are very long-lived(e.g., Atkinson & Shiffrin, 1968). Failures of long-term memory are assumed to be due to retrieval failures (e.g., Shiffrin, 1970) and to processes such as context change and interference (e.g., McGeoch, 1932). Modest support for extremely long retention comes from a variety of case studies in which material is originally well learned, is arguably unrehearsed or unretrieved over long subsequent periods, and is then shown to exhibit clear evidence of retention. Examples include Bahrick (1984), Bahrick et al. (1975), Bahrick and Hall (1991), Conway et al. (1991), Squire (1989), and Stanhope etal. (1993). These examples include retention of Spanish and of the names and faces of high school classmates. As is the case in most such studies, and in the present report, it is difficult to know whether any relevant exposures have occurred during the delay period. In these examples, though, reasonable conjectures about the kinds of exposure can be made.
Here we report two more examples of long-term retention: retention over 67...