A replication of the 5–7 day dream-lag effect with comparison of dreams to future events as control for baseline matching

The dream-lag effect refers to there being, after the frequent incorporation of memory elements from the previous day into dreams (the day-residue), a lower incorporation of memory elements from 2 to 4 days before the dream, but then an increased incorporation of memory elements from 5 to 7 days before the dream. Participants (n = 8, all female) kept a daily diary and a dream diary for 14 days and then rated the level of matching between every dream report and every daily diary record. Baseline matching was assessed by comparing all dream reports to all diary records for days that occurred after the dream. A significant dream-lag effect for the 5–7 day period, compared to baseline and compared to the 2–4 day period, was found. This may indicate a memory processing function for sleep, which the dream content may reflect. Participants’ and three independent judges’ mean ratings also confirmed a significant day-residue effect.