Sex, Sleep and the Law: When Nocturnal Genitals Pose a Moral Dilemma

It may seem to you that, much like their barnyard animal namesake, men’s reproductive organs the world over participate in a mindless synchrony of stiffened salutes to the rising sun. In fact, however, such "morning wood" is an autonomic leftover from a series of nocturnal penile tumescence (NPT) episodes that occur like clockwork during the night for all healthy human males--most frequently in the dream-filled rapid eye movement (REM) periods of sleep from which we’re so often rudely awakened in the A.M. by buzzers, mothers, or others.

For those with penises , you may be surprised to learn how frequently your member stands up while the rest of your body is rendered catatonic by the muscular paralysis that keeps you from acting out your dreams. (And thank goodness for that. Carlos Schenck and his colleagues [pdf] from the University of Minnesota Regional Sleep Disorders Center describe the case of a 19-year-old with sleep-related dissociative disorder crawling around his house on all fours, growling, and chewing on a piece of bacon--he was ‘dreaming’ of being a jungle cat and pouncing on a slab of raw meat held by a female zookeeper.) Scientists have determined that the average 13- to 79-year-old penis is erect for about 90 minutes each night, or 20 percent of overall sleep time. With your brain cycling between the four sleep stages , your "sleep-related erections" appear at 85-minute intervals lasting, on average, 25 minutes. (It’s true; they used a stopwatch.) I didn’t come upon any evolutionary theories or a proposed "adaptive function" of NPT, but we do know that it’s not related to daytime sexual activity , it declines (no pun intended) with age, and it’s correlated positively with testosterone levels. Females similarly exhibit vaginal lubrication during their REM-sleep, presumably with many dreaming of erect penises.

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