Much academic research is driven by curiosity, and few subjects arouse as much curiosity as sex. The universities of the world are full of people probing sexual behaviour, offering penetrating insights and laying bare what they have discovered.

For an amusing guided tour of the subject, look no further than Mary Roach's recent book, Bonk. Examples of the weird and wonderful things that go on include a 1954 research project by William Masters and Virginia Johnson, "done in a laboratory setting, amid scientific instruments and professionals in white lab coats".

It involved "couples fornicating on film ... men and women masturbating in front of other men and women ... a man scrutinising - whether in person or by watching footage - the genitalia of women having orgasm".

A later, five-year study of people getting down and dirty in their lab, often with strangers, raised the issue of whether "gender empathy" means that gay men and lesbians have better sex.

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Roach also recounts how, in 1991, a Dutch anthropologist and her partner, both fortunately with a background as amateur acrobats, had sex in a magnetic resonance imaging tube only 20 inches high.

Certain themes soon emerge from Roach's survey of "the curious coupling of sex and science". Vast amounts of research have been devoted to the causes and cures for erectile dysfunction. Is the problem basically physiological or psychological? It can be either, and the most obvious distinguishing sign is whether the man gets erections in his sleep. There are at least two ways of checking for this: employing a nurse to watch all night and attaching a strip of perforated postage stamps to the penis.

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Equal attention has been devoted to the hormonal, physiological and psychological facets of female arousal, vaginal versus clitoral orgasms - and whether orgasm, perhaps through "uterine upsuck", increases the chance of conception. Roach even quotes a male researcher wearily reflecting that "the only conclusion I feel sure of at this point is that women are too complicated".

This may imply that sexologists often work to a fairly set agenda, trying to dole out "happy endings", as if in a slightly raunchy romantic novel, by giving men erections, women orgasms and couples children.

Their motivation has often attracted speculation or anxiety. In a sense, this is rather strange. It is far easier for most people to understand why someone should devote an academic career to sex than to, say, Iranian cinema, microeconomics or the Black Death. But it is hard to escape the feeling that some of the great sexologists were just a little bit too interested in sex.

Nonetheless, figures such as Havelock Ellis, Alfred Kinsey and Masters and Johnson performed at least one liberating function. Because they were both curious and unshockable, they called attention to the sheer variety of common sexual feelings, fantasies and behaviour.

And that often lifted huge burdens of misery and guilt, as people who had been ashamed of their apparently unique "perversions" suddenly found themselves in good company. There is something to be said for studying sex "for its own sake".

So what kind of sex research is going on in Britain today? Roach's investigations for Bonk took her to Denmark and Germany, Egypt and Taiwan, as well as all over the US, but comparatively few of the projects she reports on are British.

Roach mentions research by UK gynaecologist Gillian Lloyd and her colleagues that, with the aim of reassuring individual women, "sought to document the truly remarkable degree of variation in the size and shape of women's genital features".

Others have considered pheromones, pelvic-floor exercises, electroejaculation and the possible health benefits of orgasm. There may be one or two other examples, but does the academy still operate largely on the principle of No Sex Please, We're British?

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On one level, of course, the answer is no. Sex is central to many issues of public health and social policy, so there are inevitably many people looking into it. Medics, psychologists, biologists, sociologists, psychoanalysts, feminists and queer theorists all bring in a range of different perspectives.

Yet none of this work requires separate departments of sexology, the kind of place where a curious researcher can investigate, say, the proportion of the population that enjoys bondage.

Both prestige and funding tend to flow in fairly predictable directions - towards anything medically useful and away from anything that sounds "pervy". And this can present a number of problems.

"The label 'sexologist' isn't routinely used in Britain," explains Petra Boynton, lecturer in international health services research at University College London, who has received an award from The Guardian as "the UK's first evidence-based agony aunt". "Sex is researched across many disciplines but there are no certificated courses in sexology, focusing on sexual functioning and behaviour."

Arguing that "much so-called sex research is actually PR surveys", Boynton suggests that we need to look at "issues of funding and institutional and public priorities".

Although "we are living in a highly sexualised culture", she adds, "many articles have a moral or negative undercurrent".

The much-used Masters and Johnson human sexual response cycle, Boynton has written elsewhere, was "developed from research on participants who volunteered to have sex in a laboratory setting and were able to function sexually in those circumstances. It is then used as a standard to assess other people and, where appropriate, to offer them 'training' to help them 'perform' while attached to various monitoring devices." This, she notes, is rather like judging ordinary people's singing ability by the standards of international recording artists.

But there are also two bigger problems that skew the research agenda. In recent times, notes Boynton, "sex conferences have become much more like medical conferences". At one she was greeted by a huge Viagra advertisement as soon as she got to the top of the escalator leading to the auditorium.

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"There is a danger of medicalising behaviour. It definitely biases research by creating a problem that requires medical intervention. We should look at other options first." This also means that it can be difficult to get funding for research into important fields such as sex and disability, which hold little appeal for the drug companies.

The other issue, in emotive areas such as prostitution or pornography, is that governments are keen to avoid recommendations or policies that will play badly in the tabloids or lose them votes.

This can put pressure on the kind of research they commission. An example, claims Boynton, is Big Brothel: A Survey of the Off-Street Sex Industry by Julie Bindel and Helen Atkins for the Poppy Project (set up to provide support for women trafficked into prostitution, funded by the Office for Criminal Reform). This was backed by Minister for Women and Equality Harriet Harman and released last month to lurid headlines such as "Full sex available for 15 quid".

Boynton was one of signatories to An Academic Response to Big Brothel, sent to the Home Office, which called attention to the weaknesses of the report. They pointed out that the research was carried out by an organisation committed to the notion that prostitution is itself "a form of violence against women", that it ignored earlier studies and that it relied largely on responses to "telephone calls made by male 'researchers' presenting themselves as potential clients".

This raised a number of ethical issues. But it also meant, argued the academics, that any information the men received about the age and ethnicity of the sex workers, and the nature of the services provided, was merely "a snapshot of the marketing process to encourage clients to visit" and could not be taken at face value.

Such are some of the problems that arise with sex research linked into sensitive questions of public policy.

So sexology as a separate discipline hardly exists within British universities. Yet, paradoxically, there is a good deal of work devoted to exploring, analysing and critiquing the whole sexological project.

A group called Critical Sexology holds seminars on themes such as intersex (people born with ambiguous genitalia) and non-monogamies. One of the organisers is Lisa Downing, professor of French discourses of sexuality at the University of Exeter.

She is also founder and director of Exeter's Centre for the Interdisciplinary Study of Sexuality and Gender in Europe, which carries out research into the history and theories of sexuality from the 19th century onwards (one of her own specialisms), the history of feminism and the body in contemporary culture.

Downing sees her work as "underpinned by feminist energies, energies of social justice and equality". "Even if sexology itself doesn't exist as a discipline in the UK," she says, "things that occurred historically are still affecting us."

And unlike researchers funded by obviously interested parties such as pharmaceutical companies or government departments, she believes that "the academy can ask more dispassionate questions because we are not directly or materially profiting from them.

"We can show up blind spots and hypocrisies, constantly bringing historical analysis to bear on the present. I think history is probably the most important perspective to bring to sex research when trying to understand that it is value-laden rather than scientifically 'neutral'. When we think how recently homosexuality was considered a mental disorder, we get close to the truth of sexology's relativity."

A final perspective comes from another organiser of the Critical Sexology seminar series, Meg Barker. A lecturer in psychology at The Open University who also practises as a sex and relationship therapist for the National Health Service, she questions whether it is useful for medics, psychologists and so on to prescribe what is, and is not, normal sexual behaviour.

"For example, some people feeling low sexual desire may not have a problem with it and even claim the label 'asexual', whereas others might experience it as a serious handicap," she says.

This may sound quite theoretical, but Barker has also written about the much more contentious area of sadomasochism. She mentions the heterosexuality questionnaire, designed to challenge stereotypes and myths, where straight people were asked: "What do you think caused your heterosexuality?" and "Is it possible that all you need is a good gay or lesbian lover?"

Someone else imagined a "friendship planet" where people have a single exclusive friend but lots of lovers. To raise consciousness in a similar way, Barker created an exercise to demonstrate how we often get far more upset and outraged by consensual sadomasochism than by non-sexual acts (rock climbing, bikini waxing, stag-night humiliations) that are just as painful or dangerous.

Then, given her own "rather positive perspective on SM and lifelong perplexity at the mass appeal of participation in, and watching of, sporting events", Barker went on to imagine a world where the standard valuations are turned upside down: "Today we welcome our UK team of Olympic SM-ers home from Madrid where they have been demonstrating their expertise in a number of different events, including gold in Japanese rope bondage, boot-worship and co-topping ... ".

People will continue to investigate sex, both practically and theoretically, and continue to look for ways of relieving sexual unhappiness - and will, no doubt, continue to be confused by sex. Academics will continue to play a crucial role in challenging assumptions.

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