Dream report length is more dependent on arousal level than prior REM duration.

Twenty two young adult subjects (Ss) were monitored for 2 consecutive nights in the sleep laboratory. Each S was awakened three times per night: at sleep onset and during the second (REMP2) and fourth (REMP4) REM periods. Length of time in each REMP prior to awakening was either 5 or 10 min, counterbalanced on successive nights. Sleep mentation reports were obtained by standardized interview and scored for total word count (TWC). TWC after 5 min of prior REM sleep did not differ significantly from TWC after 10 min of prior REM sleep. However, mean TWC from REMP4 awakenings was almost twice that from REMP2 awakenings. These findings are consistent with the hypothesis that the amount of recall from experimental REM awakenings depends on central arousal level and its effects on mnemonic processes.