SCIENCE has looked into some strange things over the centuries — reports of gargantuan sea monsters, purported images of Jesus, sightings of alien spaceships and so on. When I first heard of spontaneous orgasm, while researching a book on yoga, including its libidinal cousin, tantra, I figured it was more allegory than reality and in any event would prove beyond the reach of even the boldest investigators.

Well, I was wrong. It turns out science has tiptoed around the subject for more than a century and of late has made considerable progress in determining not only the neurophysiological basis of the phenomenon but also its prevalence. Men are mentioned occasionally. But sex researchers have found that the novel type of autoerotism shows up mainly in women.

Ground zero for the research is Rutgers University, where scientists have repeatedly had female volunteers put their heads into giant machines and focus their attention on erotic fantasies — the scans reveal that the pleasure centers of their brains light up in ways indistinguishable from everyday orgasms. The lab atmosphere is no-nonsense, with plenty of lights and white coats and computer monitors.

Subjects often thrash about so forcefully that obtaining clear images of their brains can be difficult.