News Release

November 15, 2004
For Immediate Release
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Contact: Patrick McNamara

While You Were Sleeping

A girl sleeping

Science has long been occupied with understanding our unconscious, and what is really going on when we dream. Now, a study of dream and sleep state activity has revealed that when we dream it's usually about social interactions, and that our emotional state in those interactions - whether we're friendly or aggressive - varies predictably depending on the stage of sleep we're in.

These findings are presented in the study "A 'Jekyll and Hyde' Within: Aggressive versus Friendly Interactions in REM and NREM Dreams," by Patrick McNamara, Deirdre McLaren, Dana Smith, and Ariel Brown, Boston University School of Medicine, and Veterans Administration Boston Healthcare System, and Robert Stickgold, Harvard Medical School. The study will appear in the February 2005 issue of Psychological Science, a journal of the American Psychological Society.

It has become relatively common knowledge that sleep involves two very different types of brain states: rapid eye movement sleep, or REM, and non-REM sleep, or NREM. What may not be as widely known is that during REM sleep there is intense activation of emotional centers, while NREM involves patterns of synchronized activity across the sensory and cognitive centers of the brain.

The researchers looked at whether these differing brain activation patterns for REM and NREM meant that dreams were also different. Using the "Nightcap" monitoring system, in which a specially-designed apparatus is worn on the head during sleep to record eye movement patterns, research participants were randomly awakened at different times of the sleep/wake cycle and immediately tape-recorded their dreams or thoughts. These dream and wake reports were later scored for number and variety of social interactions.

The researchers found that 1) social interactions were more likely to be depicted in dream than in wake reports; 2) dreamer-initiated aggressive social interactions were more characteristic of REM than NREM or wake reports and 3) dreamer-initiated friendly interactions was more characteristic of NREM than REM.

These findings indicate that simulations about social interactions are performed while "off-line" during the dream state, with REM specializing in simulation of aggressive and NREM of friendly interactions. It is not yet known whether these dream simulations have any effect on, or consequences for daytime social interactions.

For more information, contact McNamara at A full copy of the article is available at the APS Media Center at McNamara's recent book on sleep and dreams, An Evolutionary Psychology of Sleep and Dreams is published by Praeger Press.

Psychological Science is ranked among the top 10 general psychology journals for impact by the Institute for Scientific Information. The American Psychological Society represents psychologists advocating science-based research in the public's interest.