Sex, Drugs and Chocolate: The Science of Pleasure. Paul Martin

‘dildo’ also meant the chorus of a song. However, ‘fading’ was contemporary slang for orgasm and ‘jump and thump’ was innuendo for the process by which ‘fading’ is usually achieved. Shakespeare’s real intention is clear, even if his words are deliciously ambiguous.

      Detailed practical advice on hardware for enhancing sexual pleasure could be found in the Kama Sutra, a Sanskrit treatise dating from the fourth century AD. Among other things, it suggests that a man may improve his partner’s pleasure by fitting devices, or Apadravyas, to his penis to supplement its length or thickness. These devices, it says, should be made of gold, silver, copper, iron, ivory, buffalo horn, tin or lead; they should also be ‘soft, cool, provocative of sexual vigour and well fitted’. In the absence of expensive raw materials, various makeshift alternatives are recommended, including the tubular stalk of the bottle gourd or reeds softened with oil and tied to the waist. The Kama Sutra also explains how a man can insert solid objects into the shaft of his penis to stimulate his partner. The ancient practice of using penile nodules continues to this day in parts of Southeast Asia, central Europe and the Middle East. In the 1990s, a medical journal recorded the case of a Fijian man who had got into difficulties after whittling his own penile nodules out of a plastic toothbrush handle.

      One of the most imaginative applications of technology in the service of sexual pleasure has to be the Anal Violin. This ingenious contraption is featured in a nineteenth-century anthropological treatise written by a French army surgeon under the pseudonym of ‘Dr Jacobus X’. The good doctor, who spent much of his career in Asia, encountered the Anal Violin whilst visiting a Chinese male brothel in what is now Vietnam. He described it as long, thin and oval-shaped, about five inches in length and just over an inch in diameter at its widest. It was hollow and made of very thin silver, with the back end open and flared outwards, like a child’s trumpet. A thin metal cord, like a piano string, was fixed inside the front end and extended out of the open back for about three feet, terminating in a handle. The device was deployed by inserting it into the anus of the kneeling ‘erotic melomaniac’. The Anal Violinist then proceeded to play the instrument by rubbing the string with a metal bow to create pleasant harmonies and good vibrations. According to Dr X, ‘this Chinese symphony produces the most peculiar physiological sensations, and is certain to cause an erection in the old, worn-out debauchee who uses it.’

Pleasure, distilled

      Sexual pleasure obviously amounts to more than just the creation of orgasms. That said, orgasms do have a lot to recommend them. An orgasm is one of the most intense, if regrettably brief, forms of pleasure a human can ever experience. It is pleasure, distilled. Every one of the 6.6 billion or so humans currently alive on our planet was the result of at least one orgasm, and between us we notch up several hundred million new orgasms every day. Even allowing for the pitifully short duration of an orgasm, this still amounts to a fabulous quantity of pleasure.

      How long does an orgasm last? Scientists have attempted to answer this question objectively, confirming along the way that women’s orgasms generally last longer than men’s. Researchers in one study monitored young women who gave themselves orgasms in the laboratory. Measurements of their vaginal blood flow indicated that these lasted on average 20 seconds, although half the women felt subjectively that their orgasms were of shorter duration. Incidentally, Meg Ryan’s legendary fake orgasm in the film When Harry Met Sally also lasted 20 seconds, making it convincing even in its duration. Many women experience longer orgasms. According to physiological measures and women’s own subjective estimates, these longer orgasms may last between 30 and 60 seconds, with some going on for up to two minutes. Much depends, of course, on where you judge an orgasm to start and end. Even so, a 60-second full-on orgasm would make most men’s year. The typical male orgasm is much shorter, at around 10–15 seconds.

      Some women are able to reach orgasm using mental imagery alone, without any physical stimulation. Scientists have verified this by demonstrating that imagery-induced orgasms are accompanied by more or less the same physiological reactions as mechanically induced orgasms, including the characteristic increases in heart rate, systolic blood pressure, pupil diameter and pain threshold. The ability to have an orgasm without the help of mechanical stimulation is not as remarkable as it might seem, since most men and women are quite capable of having orgasms during their dreams. However, the evidence indicates that fewer than one in a thousand men are capable of achieving orgasm when they are awake without some mechanical assistance.

      Many women also experience the delights of multiple orgasms, something that few men even pretend they can do. Of the few men who are capable of multiple orgasms, most do not ejaculate until the final orgasm in the sequence. There has, however, been at least one documented case of a man who could achieve multiple orgasms, each of which was accompanied by ejaculation. The man in question demonstrated this extraordinary ability to scientists in a laboratory, ejaculating six times in 36 minutes while maintaining an erection throughout.

      The changes in brain activity that accompany orgasm are similar in many respects to those observed during other forms of highly rewarding or pleasurable activity, including the consumption of recreational drugs. Many different parts of the brain are activated during orgasm, among them the nucleus accumbens and the anterior cingulate. As we shall see later, these two brain regions play prominent roles in mediating the experience of pleasure. We know that these areas of the brain are more active during orgasm because doughty volunteers have been willing and able to push back the frontiers of knowledge by masturbating to orgasm inside a functional magnetic resonance imaging (fMRI) machine.³

      Orgasm is accompanied by involuntary muscle contractions in the perineum and rectum. Needless to say, scientists have measured these as well. In one study, researchers at the University of Groningen in the Netherlands persuaded twenty-three healthy women to have a measuring instrument inserted into their rectum to record these muscle contractions. The women were then monitored while having real orgasms, produced by clitoral stimulation, and also when faking orgasms. The data revealed that when a woman has a genuine orgasm – as opposed to a fake one – her rectum palpitates at a frequency of between 8 and 13 hertz (cycles per second). Fluctuating rectal pressure in the frequency band 8–13 hertz was an accurate indicator of genuine clitoral orgasm. Faking an orgasm, or masturbating to just short of orgasm, did not generate this signature response.⁴

      Orgasm also triggers the release of the hormone oxytocin, a substance which is perhaps better known for stimulating the flow of milk from the breasts. Oxytocin contributes to the formation of the pair-bond between sexual partners. Some of the clearest evidence for this comes from research on voles. In monogamous prairie voles, an adult male forms a strong pair-bond with one female and helps her care for their offspring. When they first get together, the male and female have sex twenty or more times in a day, which makes them very fond of each other. These animals have high oxytocin levels and large numbers of oxytocin receptors in their brain. If a female’s oxytocin receptors are artificially blocked, she does not pair-bond with a partner. By contrast, a closely related species of vole behaves promiscuously; the males of this species, who mate with many different females, have lower oxytocin levels and fewer oxytocin receptors in their brain. This and other evidence implies that oxytocin plays an important role in pair-bonding, probably by acting on reward centres in the brain.⁵ One interpretation is that monogamous males become hooked on the pleasure of having sex with their mate. Recent research on humans has shown that spraying oxytocin up someone’s nose makes them more trusting towards other people. We shall return to the subject of trust in the final chapter, in view of its curious relationship with pleasure.

      Oxytocin may have some bearing on the anecdotal observation that human drug addicts find it easier to quit their drug habit if they fall in love. Experiments have shown that giving oxytocin to rats or mice reduces their voluntary consumption of heroin and makes them more resistant to becoming tolerant to morphine and alcohol. Oxytocin also alleviates the symptoms of morphine withdrawal and reduces the behavioural effects of cocaine, especially the hyperactivity and stereotyped