Sixteen women were awakened from REM periods (two nights) and questioned about the novelty of the physical surroundings, characters, activities, and social interactions of their dreams. Each content element and overall dream was assigned to one of six novelty categories, ranging from exact replication of waking experience to not previously experienced and highly improbable that it could be experienced. A relatively high proportion of physical surroundings and characters were novel in the sense of not having been encountered in waking life, but not in the sense of being unusual. Activities, social interactions, and overall dreams were distributed between the extremes of exact replication and high improbability. The incidence of novelty in the sense of both not having been previously experienced and being highly improbable was relatively rare in all content areas. There was evidence of greater dream novelty later in the night and of stable individual differences in novelty distribution.
Dorus E, Dorus W, Rechtschaffen A. The Incidence of Novelty in Dreams. Arch Gen Psychiatry. 1971;25(4):364-368. doi:10.1001/archpsyc.1971.01750160076014