Studies of implicit prototype extraction in patients with mild cognitive impairment and early Alzheimer's disease

Robert M. Nosofsky, Stephen E. Denton, Safa R. Zaki, Anne F. Murphy-Knudsen, Frederick W. Unverzagt

Research output: Contribution to journalArticle

17 Scopus citations


Studies of incidental category learning support the hypothesis of an implicit prototype-extraction system that is distinct from explicit memory (Smith, 2008). In those studies, patients with explicit-memory impairments due to damage to the medial-temporal lobe performed normally in implicit categorization tasks (Bozoki, Grossman, & Smith, 2006; Knowlton & Squire, 1993). However, alternative interpretations are that (a) even people with impairments to a single memory system have sufficient resources to succeed on the particular categorization tasks that have been tested (Nosofsky & Zaki, 1998; Zaki & Nosofsky, 2001) and (b) working memory can be used at time of test to learn the categories (Palmeri & Flanery, 1999). In the present experiments, patients with amnestic mild cognitive impairment or early Alzheimer's disease were tested in prototype-extraction tasks to examine these possibilities. In a categorization task involving discrete-feature stimuli, the majority of subjects relied on memories for exceedingly few features, even when the task structure strongly encouraged reliance on broad-based prototypes. In a dot-pattern categorization task, even the memory-impaired patients were able to use working memory at time of test to extract the category structure (at least for the stimulus set used in past work). We argue that the results weaken the past case made in favor of a separate system of implicit prototype extraction.

Original languageEnglish (US)
Pages (from-to)860-880
Number of pages21
JournalJournal of Experimental Psychology: Learning Memory and Cognition
Issue number4
StatePublished - Jul 2012


  • Amnesia
  • Categorization
  • Explicit memory
  • Implicit learning

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Language and Linguistics
  • Linguistics and Language
  • Medicine(all)

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