Temporal delays in incorporation of events into dreams

20 subjects viewed an emotionally arousing video and then recorded their dreams at home for seven nights. Dreams were subsequently rated for the likelihood that some aspect of the video had been incorporated. For subjects who showed strong evidence of incorporation, mean likelihood of incorporation ratings followed a U-shaped pattern, with significantly higher scores on Nights 1, 6, and 7 than on Night 4. The similarity of this temporal pattern with REM sleep patterns observed in rats exposed to various learning experiences is noted, and the role of the hippocampus as a possible neural mechanism for delayed incorporations is discussed.