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Bizarreness effect in dream recall.

Carlo Cipolli, R Bolzani, C Cornoldi, R De Beni, Igino Fagioli

Sleep February 1993 DOI: 10.1093/sleep/16.2.163 (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational study Peer reviewed
Sample size 10
Population People awakened during REM sleep in a sleep laboratory
Duration 4 nonconsecutive nights, with three awakenings per night
Topics Dreaming
Key findings Bizarre dream content was roughly twice as likely as nonbizarre content to appear in both night and morning reports, and the proportion of shared bizarre content increased with the amount of bizarre content in the night report. The authors argue this indicates bizarreness enhances recall of dream contents via richer encoding at the moment of dream generation, which they suggest may explain why everyday dreams, recalled after longer intervals, seem more bizarre than those recalled in the laboratory.

Abstract

This study aimed to ascertain a) whether morning reports of dream experience more frequently reproduce bizarre contents of night reports than nonbizarre ones and b) whether this effect depends on the rarity of bizarre contents in the dream or on their richer encoding in memory. Ten subjects were awakened in rapid eye movement (REM) sleep three times per night for 4 nonconsecutive nights and asked to report their previous dream experiences. In the morning they were asked to re-report those dreams. Two separate pairs of judges scored the reports: the former identified the parts in each report with bizarre events, characters or feelings and the latter parsed each report into content units using transformational grammar criteria. By combining the data of the two analyses, content units were classified as bizarre or nonbizarre and, according to whether present in both the night and corresponding morning reports, as semantically equivalent or nonequivalent. The proportion of bizarre contents common to night and morning reports was about twice that of nonbizarre contents and was positively correlated to the quantity of bizarre contents present in the night report. These findings support the view that bizarreness enhances recall of dream contents and that this memory advantage is determined by a richer encoding at the moment of dream generation. Such a view would seem to explain why dreams in everyday life, which are typically remembered after a rather long interval, appear more markedly bizarre than those recalled in the sleep laboratory.

Comparable studies

Other observational and cohort studies on dreaming, most cited first.

Study Year Design Participants
Lucid Dreaming: a State of Consciousness with Features of Both Waking and Non-Lucid Dreaming Student volunteers trained to become lucid and signal lucidity with horizontal eye... 2009 Observational study n = 6
Nightmare Prevalence, Nightmare Distress, and Self-Reported Psychological Disturbance Young adults with a mean age of 20 years 2002 Prospective observational study n = 116
Long-term effects of extreme situational stress on sleep and dreaming Survivors of traumatic events who complained of sleep disturbances, compared with... 1987 Case-control study n = 11
The relationship of nightmare frequency and nightmare distress to well‐being Adults who reported dreams 2004 Observational cohort n = 147
Dreaming in NREM Sleep: A High-Density EEG Study of Slow Waves and Spindles Healthy human subjects 2018 Observational cohort n = 14

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