Not all repetition is alike: Different benefits of repetition in amnesia and normal memory

Abstract

While it is well known that repetition can enhance memory in amnesia, little is known about which forms of repetition are most beneficial. This study compared the effect on recognition memory of repetition of words in the same semantic context and in varied semantic contexts. To gain insight into the mechanisms by which these forms of repetition affect performance, participants were asked to make Remember0Know judgments during recognition. These judgments were used to make inferences about the contribution of recollection and familiarity to performance. For individuals with intact memory, the two forms of repetition were equally beneficial to overall recognition, and were associated with both enhanced Remember and Know responses. However, varied repetition was associated with a higher likelihood of Remember responses than was fixed repetition. The two forms of repetition also conferred equivalent benefits on overall recognition in amnesia, but in both cases, this enhancement was manifest exclusively in enhanced Know responses. We conclude that the repetition of information, and especially repetition in varied contexts, enhances recollection in individuals with intact memory, but exclusively affects familiarity in patients with severe amnesia. (JINS, 2008, 14, 365-372.)

Impaired capacity for familiarity after hippocampal damage

“…Other studies have also used the Remember-Know procedure to assess the capacity of recollection and familiarity in memoryimpaired patients with lesions that include the hippocampus (11)(12)(13)(14)(15)(16)(17). Patients typically exhibit a markedly reduced frequency of R responses but only a modest reduction (or no reduction) in the frequency of K responses.…”

“…Participants were instructed to use the entire scale. For words declared old (ratings of [11][12][13][14][15][16][17][18][19][20], participants also judged whether the word was recollected, was familiar, or was a guess, following a Remember-KnowGuess procedure (9,26). The modified instructions emphasized that participants should use the R response only if they could actually describe specific details about the experience of studying the word.…”

“…We next examined performance separately for R and K responses when the two kinds of responses were matched for memory strength at a high-confidence level (ratings of [17][18][19][20]. As one might expect, when high-confidence ratings were given, both groups tended to perform rather well.…”

“…For words declared old (ratings of [11][12][13][14][15][16][17][18][19][20], participants then judged whether the word was recollected (Remember), was familiar (Know), or was a guess (Guess). Then, to examine the frequency of R and K responses in each group after removing the effect of memory strength, we compared performance for items endorsed with high confidence (ratings of [17][18][19][20].…”

A demonstration that the hippocampus supports both recollection and familiarity

“…Accordingly, if recollection were selectively impaired, Know judgments should be especially common after hippocampal lesions. In such studies, amnesic patients have sometimes (18,19), but not always (20,21), exhibited a higher frequency of Know judgments than controls (as if they experience the butcher-onthe-bus phenomenon more often than controls). However, in recent years, much evidence has accumulated showing that, despite receiving standard instructions, participants usually make Know judgments for Old decisions that are associated with lowto-medium confidence, not high confidence (22)(23)(24).…”