Men think about sex every seven seconds, right? And the nature of their intimate thoughts? Being fawned over by two women simultaneously, probably with a bit of Sapphic action thrown in.

Not quite. By most accounts, the extent of men’s lustful imaginings is more humdrum. The average man fantasises at least once a day, and the most common fantasy comprises sex with a known partner. Even this is up for debate: face-to-face sex surveys are notoriously unreliable at uncovering the truth. After all, how many of us are happy to reveal our unexpurgated thoughts to a stranger?

Now a team of psychologists at Leeds University, led by Dr Mitch Waterman, is aiming to conduct a definitive study of male sexual fantasy. The anonymous, confidential survey, which can be completed by any male aged between 18 and 90, is planned to capture the entire spectrum of men’s sexual thoughts. What do men think about, and how often do they think it? The use of the phrase “sexual thoughts” rather than “sexual fantasies ” is a deliberate attempt to encompass anything and everything that passes through a man’s mind relating to sex. Absolutely nothing is off-limits — bestiality, rape, sadism, children, group sex — because the researchers have no real idea about how ordinary, weird or just plain disturbing men’s fantasies can be.

“Fantasising is normal, and what counts as normal is extremely broad,” says Waterman, who is conducting the survey with Tamara Turner-Moore, a PhD student, and Dr Paul Smith. The origin of the seven-second statistic, a favourite of glossy magazines, is a mystery; more reliable research credits men with being able to think outside the bed. The Kinsey Institute at Indiana University suggests that 54 per cent of men think about sex at least every day, 43 per cent think about it a few times a week or month, and 4 per cent once a month or less. All men are different, though; some, Waterman says, will think about sex many times daily.

Previous studies suggest that nearly all men, 91 per cent upwards, fantasise. Men are reported to fantasise less as they get older (whether content changes is uncertain); a frequently exercised imagination is associated with fewer sexual difficulties. Sexually experienced men are reported to fantasise more, probably because they have a richer repertoire of material from which to pluck their scenarios. As might be expected, heterosexual men tend to think about women; homosexual men about men. The fantasy about two women also crops up, although probably not as often as men’s magazines would have us believe.

“Research suggests that the most common sexual fantasy in men is a conventional fantasy such as sex with a loved partner,” says Turner-Moore. That “loved partner” might be current or past. Waterman is cautious even about this: do wives and girlfriends really feature, or do most men secretly muse on females of lesser acquaintance? As well as re-asking the conventional questions, the Leeds researchers hope to explore the more outlandish reaches of sexual fantasy. How common, for example, are shoe fetishes or fixations on gas masks (a peculiarly British sexual peccadillo)? Some men are known to imagine sex with animals, sex with children, or forcing themselves on someone.

Bestiality, paedophilia and rape, in other words. This is where sexual fantasy has the potential to cross over from the titillating to the terrifying, where the amusing sexual foibles and fetishes documented by the likes of Cosmopolitan and Maxim become disturbing tales of sexual preoccupations leading to criminal behaviour.

What, if anything, distinguishes a man who likes his wife to dress up as a schoolgirl in consensual sex from a man who grooms under-age schoolgirls for sordid encounters? The researchers will also record the thoughts of sexual offenders, who have turned illicit fantasy into illegal reality.

Given the history of sex research, it is regarded as unhelpful to talk about deviancy. Gay fantasies were once considered deviant; homosexuality is now legally and, for the most part, culturally acceptable. Homosexuality has lost its status as a paraphilia, which describes an unusual, recurrent, intense sexual urge that robs a person of the ability to function normally within society.

Examples of paraphilias are paedophilia, sadism, voyeurism and exhibitionism; individuals devoted to unusual sexual practices are overwhelmingly male. Fetishism is another paraphilia, and it comes in an astonishing variety: there are people for whom sexual gratification is impossible without a stiletto shoe or a piece of rubber. Or, as Waterman tells me, a gas mask: “Britons are supposed to be obsessed with gas masks, because of the Blitz. The masks became associated with early sexual activity, so it’s almost an accidental link.”

Some of the stranger fetishes, he says, make sense only in terms of “learning theory”, which suggests that, during childhood, some people come to associate certain objects with sexual activity, and that the link escalates into a dependence that excludes normal human sexual contact.

He explains: “There’s a famous case in the literature where a boy developed a fetish for radio static. The story goes that before puberty he would go upstairs and rock on his rocking horse, and he found that sexually stimulating. He would tune his radio until it was between channels, so it blocked out the sound of his parents arguing. In time, the radio static became linked to the idea of sexual activity, and this link was reinforced because he would climax at the end of it.”

For others, the focus of sexual attention might not be a person or an object but an animal, as in the case of a man who thought he was having a relationship with a female horse. When the mare showed interest in a stallion, the man punctured the female horse’s womb in a fit of jealousy. “We can assume people fantasise about animals because they have sex with animals, although it’s a minority,” Waterman says. “Farm animals crop up, because of accessibility, so we’re talking about sheep, cows, goats and pigs. There’s almost certainly a lot happening between dog owners and their dogs but dog owners don’t tend to get caught and prosecuted.” Turner-Moore adds that the highest rates for bestiality are in rural areas, suggesting an opportunistic element to some sexual behaviour.

Surely it isn’t normal for a grown man to love a female horse? “I think we can guess that in the context of most people’s everyday thoughts, bestiality is abnormal,” Waterman admits. “But to label it as anything other than that would be strictly inaccurate. It’s certainly unconventional.”

The researchers also distinguish between thinking something and doing it. For example, it is common for people to have non- sexual fantasies — such as exacting revenge on a hated ex-spouse — that they would never carry out. They suspect the same is true of sexual fantasies. An estimated 35 per cent of men admit to fantasising about rape. Waterman says: “If someone fantasises about rape, or forced sex, and does nothing about it, then to argue that that fantasy is abnormal has to be seen as controversial because the literature suggests that rape is a common fantasy. But if a person acts on their fantasy and rapes someone, that’s considered deviant.”

Sexual thoughts about children are another controversial area. Between 4 and 9 per cent of men report sexual fantasies involving children, with the age of the imagined children usually unspecified.Men are known to prefer younger women, because, as evolutionary theory would have it, youth represents fertility. So should we worry about men who have schoolgirl fantasies?

“We don’t yet know whether we should classify such thoughts as deviant or not,” says Turner-Moore. “We don’t know whether there is anything different between men who just fantasise about children, and men who fantasise about children and also commit offences against children.”

Waterman and his colleagues are wary of straying into “thought police” territory, or of appearing judgmental. Bizarre thoughts, they say, pop up in everyone’s mind from time to time, and, like dreams, can be beyond conscious control. In any case, Waterman points out, our own psyche is usually capable of reining in some fantasies — through guilt. “The message has to be that the deviation lies not in the thinking but in the action. And guilt is almost certainly an important message about the action. That’s what the feeling is for. So a little bit of guilt about a naughty thought may not be inappropriate.”

Fantastic findings from the Forties and Fifties

In his landmark research in the Forties and Fifties, the sexologist Alfred Kinsey found the following: