Sleep on it? Re-examining the Impact of Sleep on Memory

David Morgan

Research output: ThesisDoctoral Thesis

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Sleep is widely believed to play an active role in memory consolidation – the process by which memories are stored. Many studies have demonstrated that sleep yields greater memory performance on various tasks in comparison to an equivalent period of wake. However, the studies conducted in this thesis reveal a divergent pattern of results which do not consistently demonstrate the benefits of sleep on memory. The first study, a registered report and the largest sleep vs. wakefulness comparison to date (N = 4,000), examined the impact of sleep on eyewitness identification performance. It was predicted that sleep compared to wake would benefit accuracy. The data did not support that prediction: there were no differences between sleep and wake. The second study used the questionnaire data collected as part of the registered report (N = 7,533) to provide normative data of sleepiness scales and sleep duration for clinicians and researchers alike to use. The third study, a conceptual replication and extension of previous research, investigated the impact of sleep on integrating true and false information which would reduce memory accuracy. Sleep was not detrimental to memory accuracy, nor was there strong evidence that it was beneficial. Given the absence of the purported effects of sleep in these experiments, a replication experiment was designed to re-examine well-known findings of sleep on memory. We attempted to replicate research indicating that sleep preferentially benefits the consolidation of emotional stimuli. No evidence was found in support of these findings, but there was a sleep benefit on overall memory (however there was also a potential time of day confound). Potential explanations for the mixed findings are considered and large-scale replication efforts are proposed to clarify understanding of the benefits of sleep on memory.
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Tamminen, Jakke, Supervisor
  • Mickes, Laura, Supervisor
Thesis sponsors
Award date1 Apr 2020
Publication statusUnpublished - 2020


  • Sleep
  • Memory
  • Eyewitness Identification

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