In their recent paper entitled "Sex Dreams, Wet Dreams, and Nocturnal Emissions" (Dreaming, 2011, Vol. 21, No. 3, 197-212), Calvin Kai-Ching Yu and Wai Fu from Hong Kong Shue Yan University note that rigorous empirical studies of sex dreams are few and far between. Even though REM sleep is associated with prolonged erections in the male and clitoral engorgement and pelvic thrusting in the female, scientists have not pursued these leads concerning potential functions of REM sleep.

Freud, however, was not as timid as modern psychological or biomedical scientists. Although he was not aware of the striking physiological sexual associations with REM sleep (nor indeed was he aware of REM sleep), he nevertheless correctly guessed or inferred that dreams had something to do with libidinal desires. When these libidinal desires conflicted with societal or moral norms they were repressed and then covered over with elaborate dream symbols and images. For Freud, dream interpretation all too often reduced to wading through the thicket of symbolic camoflauge thrown up by the dream machine in order to rediscover the original libidinal wishes that gave rise to them in the first place.

Yu and Fu give due respect to Freud's work but move beyond it by providing a neural model of dreaming that is consistent with the modern cognitive neurosciences. Their model is similar to the one suggested by Mark Solms several years ago. Libidinal desires are thought to be mediated by meso-limbic-cortical dopaminergic systems. The prefrontal cortices act to regulate and inhibit aggressive and libidinal desires. During REM sleep activation of the dopaminergic systems are heightened and the prefrontal regulatory systems are weakened. Since libidinal desires cannot be acted upon during sleep their satisfaction is hallucinated and these hallucinations are called dreams. Freud had originally suggested a very similar model and added that the hallucinations act to protect sleep.

Yu and Fu's study was simple in design. They gave a questionnaire on sex dreams to 58 young male college students but unlike previous studies the questionnaire included a fairly extensive list of sexual activities that respondents could indicate they had dreamed about. The list included such activities as kissing lips, foreplay, vaginal intercourse, oral intercourse, and anal intercourse. Finally the authors asked respondents to indicate if they had ejaculated during a dream whether or not the ejaculation was in response to a dream image.

Results showed that 95% of respondents (all of whom were male remember) had dreamed about sex with a woman, with the most common forms of sexual interaction being foreplay and vaginal intercourse. Most respondents reported that they dreamed of vaginal intercourse with a woman about 9 times a year. Approximately 80% of respondents reported having had a wet dream at least once. Interestingly, the women these young men dreamed about were most often complete strangers. In about a third of the sample the objects were female teachers. In about 10% of cases the objects were mothers of the dreamers. Almost 12% of heterosexual participants had dreamed about engaging in various types of homosexual activities.

What should we make of these intriguing findings? Can they tell us anything about the functions or meaning of dreams? On the one hand the findings are banal. Should we be surprised that young men have sex dreams that involve fantasy objects or women they see on a daily basis? I am more surprised that sex dreams in these young men are not more frequent than 9 times a year. Can this negative result (the relative infrequency of sex dreams) be attributed to a social desirability effect? Were respondents just giving the researchers a watered down sanitized version of their dream lives? I do not think so. Yu and Fu's results are consistent with other studies and responses were anonymous. They could have responded anyway they wished and no-one would have guessed who they were.

So then what do results tell us about dreams? Even when we ask young men about sex dreams it turns out that sex dreams are relatively rare occurring only about nine times a year! Similar results are obtained from young women. Dreams seem not to be primarily about sex.

Given that sex is a central desire or concern for most people, particularly young people it cannot be that dreams are primarily reflections of everyday desires, affairs or concerns. Dreams have no consistent continuity with everyday life and therefore the continuity hypothesis of dreams (an all too popular theory of dreams these days) must be false.

What about Freud's claims concerning the disguise of libidinal wishes in dreams? Yu and Fu find some evidence for this idea in their data but I confess I see no such evidence for Freud's position in any dataset on dreams that I have seen. Instead sex dreams are pretty explicit simulations of sexual interactions. Likewise dreams not involving sex appear to be about whatever themes they are about--not some buried libidinal drive.

Although we can conclude that we know what dreams are NOT about (everyday life), we still unfortunately do not really understand what dreams are about.

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