Dreamlike events are correlated with the length of sleep mentation reports.

We investigated the relationship between length and dreamlike quality in sleep mentation reports. Reports were obtained by waking subjects at sleep onset (SO) and at 5 and 10 minutes into the second (REMP2) and fourth REM periods (REMP4). Reports were recorded, transcribed, and scored blindly for total word count (TWC) and dreamlike quality as measured by a composite dream scale score (CDS). Dreamlike quality was strongly correlated with TWC; both CDS and TWC scores increased across successively later awakenings. Significant differences were found in both TWC and CDS between SO and REMP4 and also between REMP2 and REMP4; however, differences were not significant between SO and REMP2 or between the 5 and 10 minute awakenings in REMPs 2 and 4. These findings provide further evidence that the amount of dreamlike mentation is related to the within-sleep arousal level rather than to REMP duration and that the dreamlike quality of reports increases as they become longer.