Assessing the dream-lag effect for REM and NREM stage 2 dreams.
PLoS One January 1, 2011 Mark Blagrove, Nathalie C Fouquet, Josephine A Henley-Einion et al.
Events and memories from waking life can reappear in dreams, either literally or indirectly. Two temporal patterns are known: the day-residue effect (features from the previous day) and the dream-lag effect (features from 5–7 days earlier). Previous work used spontaneous home dream reports from both REM and NREM sleep. This study tested whether the dream-lag effect occurs only in REM or also in NREM stage 2 (N2) dreams. Twenty participants kept daily diaries for over a week, then slept in a laboratory for two nights. REM and N2 dreams were collected, and participants rated correspondence between each dream and diary entry. The dream-lag effect appeared for REM but not N2 dreams, even after accounting for dream length.