Susan lost her well-paid job in financial services. She ate less, exercised, lost weight, and looked 10 years younger. She went to the hairdresser and had her hair cut, coloured and restyled into a shorter, more flattering style that made her look younger and more lively. She went shopping, invested in an expensive new suit that showed off her new trim figure and made her look attractive as well as professional, and wore the suit to all her job interviews. Susan felt confident wearing it. She got a new consultancy job paying 50 per cent more than the old one.

Susan works in the private sector, where appearances count. But people in other sectors, including the academy, could do the same. And why not? Why wouldn't anyone invest in and deploy an asset that supplements intelligence, specialist knowledge and experience?

I coined the term "erotic capital" to refer to a nebulous but crucial combination of sex appeal, beauty and physical and social attractiveness that makes some men and women agreeable company and colleagues, attractive to all members of their society and, especially, to the opposite sex. We are used to valuing human capital - qualifications, training and work experience. More recently, we have begun to recognise the importance of networking and social capital - who you know instead of what you know.

Erotic capital is just as important as human and social capital for understanding social and economic processes, social interaction and upward social mobility. It is essential for analysing sexuality and sexual relationships. In sexualised, individualised modern societies, erotic capital is becoming more important and more valorised, for both men and women. However, women have a longer tradition of developing and exploiting it, and studies regularly find women to have greater erotic appeal than men. Artists have perceived this for centuries.

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Erotic capital is multifaceted. A central element is beauty, but there are several other factors involved, too. These include sexual attractiveness, social skills, liveliness, social presentation and sexuality itself (see box). Erotic capital is a combination of aesthetic, visual, physical, social and sexual attractiveness to other members of your society, and especially to members of the opposite sex, in all social contexts.

In affluent modern societies, erotic capital has increasing importance in all contexts. This was demonstrated clearly in the recent general election. Just a few decades ago, all the emphasis was on political party policies. Today, televised debates and endless photographs of the candidates add an extra dimension: How attractive are they? Are they smartly dressed? Do they look nice? It seems likely that the candidates' self-presentation skills, their looks and charisma all played a part in the upswing for the Liberal Democrats in opinion polls.

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Like all managers and professionals in other sectors, the academic world is affected by the rising importance of erotic capital. Students (and their parents) who incur large debts to finance long years of higher education become more demanding customers. This is even more true for students from continental Europe and overseas students paying the highest fees. They expect academics to dress smartly and take care of their appearance, like all professionals. Students can perceive casual jeans and sagging sweaters in ugly colours as insulting to a lecture audience - it says: "I couldn't be bothered to dress properly for you lot." Yes, we know he is one of the London School of Economics' top professors ... but!

Counsellors who advise on job-hunting remind us that you never get a second chance to make a good first impression. The first two lectures for any course can be crucial - not only for setting out what the course will cover and how, but also for establishing the style and attractiveness of the teacher.

In the past, most academics were just "names" - invisible, ageless names attached to theories, concepts and ideas. Today, university websites routinely display separate pages for every member of staff, almost invariably with a photograph attached. Suddenly, appearance and style matter, hugely, and we cannot remain "faceless" as in the past.

Until recently, the LSE published LSE Experts, an annual compendium produced for the media that listed its academics' fields of expertise, almost invariably with a photograph attached. Leafing through this volume became a beauty parade - one that was won by those who had used professional photos instead of amateur snaps, or even no photo at all.

Research shows that attractive people find it easier to make friends, are more likely to marry, are more persuasive in debate, are perceived to be more competent and able, are regarded as more honest and "good" generally, are more influential, are more successful in affairs and in marriage.

This means that investing time and effort in your appearance and social manners pays dividends. It is not frivolous or superficial. Indeed, several studies in North America and Britain (including the British cohort studies) show that people with average looks can earn about 10 to 15 per cent more than unattractive people, and people who are really attractive can earn about 10 to 15 per cent more than people with average looks. Several studies show the financial rewards for attractiveness to be greater for men than women - unfair again.

These studies also show that the private sector employs more attractive people than the public sector. This is partly due to self-selection, given that the private sector rewards good looks and self-presentation skills more than jobs in the public sector. It is also due to the fact that most jobs in entertainment, hospitality, sales and marketing are in the private sector, where erotic capital has commercial value. However, expectations of what constitutes acceptable or attractive appearance are rising everywhere, and affect everyone.

Academics who are physically and socially attractive as well as able specialists do appear to gain "an edge"; an extra boost in public acceptance of their work. Psychologist Steven Pinker's best-selling book The Blank Slate (2002) probably benefited from his good looks and easy charm in public presentations. He confirmed the idea of genetic differences between men and women, yet he escaped the customary feminist attack on the idea of innate sex differences.

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The handsome particle physicist Brian Cox is often referred to as the "rock-star physicist", and his physical attractiveness probably helped him as a presenter of BBC science programmes. Similarly, the success of historian Amanda Foreman's The Duchess (2008), a biography of Georgiana, Duchess of Devonshire, was possibly helped by her photogenic good looks.

Unfortunately, professional women who deploy their erotic capital are likely to get stamped on - by jealous men as well as by women. Just one example is the historian David Starkey's derision of his female competitors, branding their successful books as "pretty girl" history. Press coverage of the drama surrounding director Susan Greenfield's exit from the Royal Institution has typically included comments on her looks and style that are rarely applied to men (see box below). Even in the serious press, journalists define women in the news by their hair colour and age, whereas I have yet to see Sean Connery described as a balding old man.

Women especially are trapped in a catch-22. Their appearance is judged more harshly than men's. But if women benefit from an attractive appearance, they are chastised for it.

There have been two types of response to the online publication of my theory of erotic capital in the European Sociological Review in March. One strand is exemplified by Anthony Giddens, former director of the LSE, who commented that it is "quite brilliant ... really original and interesting". It has attracted serious attention, from Berlin to Washington, from Milan to Toronto, and there has been widespread acceptance that erotic capital is indeed the missing third personal asset, complementing human capital and social capital.

However, another reaction has been the classic puritanical Anglo-Saxon rejection of beauty, sensuality and sexuality as worthless, base, superficial and valueless, a rejection reflected in patriarchal and, more recently, feminist denial of women's erotic power as worthy of attention and reward.

Understandably, academics want to be judged solely on the basis of their expertise, intelligence and ideas. But nowadays, authors and conference speakers are identified also by the ubiquitous photograph. Perhaps we should accept that erotic capital has increasing social and economic value in the 21st century - and for good reason.

IT'S NOT JUST SEX APPEAL: CAPITAL COMPONENTS

What are the elements that make up erotic capital?

- Beauty

This is a clearly a central element, although there are cultural and temporal variations in ideas about what constitutes beauty.

Some African societies admire women with large voluptuous bodies. In Western Europe, fashion models are tall and stick-thin to the point of being anorexic.

In previous centuries, women with small eyes and tiny rosebud mouths were considered delicately beautiful. The modern emphasis on photogenic features means that men and women with large eyes and mouths and "sculpted" faces are favoured.

Studies show that conventionality, symmetry and an even skin tone contribute to attractiveness, and that it is, in part, an achieved characteristic, as illustrated by the French concept of the belle laide, an ugly woman who becomes attractive through her presentational skills. Great beauty is always in short supply and is therefore universally valorised.

- Sexual attractiveness

This element can be quite separate from classic beauty. Beauty is to some extent based on facial attractiveness, whereas sexual attractiveness is about a sexy body. But sex appeal can also stem from personality and style, femininity or masculinity, a way of being in the world, a characteristic of social interaction.

Beauty tends to be static, but sexual attractiveness is about the way someone moves, talks and behaves.

Sex appeal is often associated with youth, and it can fade rapidly with age. And the variation in personal tastes means there is no universal ideal. Some men prefer women who are small, petite, even tiny, whereas others prefer tall and elegant women. Some women prefer men with well-developed muscles and strong athletic bodies, whereas others prefer a more slender, effete, elegant appearance.

Despite this variation in taste, sex appeal is in short supply and is therefore valorised.

- Social skills

This category comprises factors that are definitely social: grace, charm, social skills in interaction, the ability to make people like you, feel at ease and happy, want to know you and, perhaps, desire you.

Flirtatious skills can be learned, but again are not universal. Some people in positions of power ooze charm and charisma; others have none at all. Some men and women are skilled at discreet flirtation; others are incapable. Again, these social skills have value.

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- Liveliness

This takes in a mixture of physical fitness, social energy and good humour. People who have a lot of "life" in them can be hugely attractive to others - as illustrated by those who are "the life and soul of the party". In most cultures, liveliness is displayed in dancing skills or sporting activities.

- Social presentation

The fifth element concerns things such as style of dress, face-painting, perfume, jewellery or other adornments, hairstyles, and the various accessories that people carry or wear to announce their social status and style to the world.

Heads of state dress for public functions to emphasise their power and authority. Ordinary people going to a party or other social event dress to make themselves attractive as well as to announce their social status and wealth to the people present or to make style statements.

The relative emphasis on sexy attire or social status statements depends on the venue and event. People skilled at social presentation appropriate to the event are more attractive than those who look like tramps.

- Sexuality

The final element is sexuality itself: sexual competence, energy, erotic imagination, playfulness and everything else that makes for a sexually satisfying partner.

Whether or not someone is a good lover is known only to their partners, and the British national sex surveys provide no information on levels of sexual competence. It seems reasonable to suppose that sexual skill is not a universal attribute, and extreme competence is a minority asset. This factor is listed last because it usually applies only in private, intimate relationships, whereas the other five can come into play in all social contexts, visibly or invisibly.

For men as well as women, all six elements contribute to defining someone's erotic capital. The value of erotic capital also depends on someone's occupation, which may or may not valorise it. As a general rule, it is of most value in situations where there is an audience, where there is a need to persuade or sell, and where people are on public display.

The social and economic value of erotic capital is highlighted in occupations in the entertainment and hospitality industries, but it can also be apparent in all social contexts, visibly or invisibly. Erotic capital helps to sell products, services, ideas and policies.

In some cultures, fertility is an additional element of women's greater erotic capital. Erotic capital includes skills that can be learned and developed, as well as advantages fixed at birth. Women generally have more of it than men, even in cultures where fertility is not an integral element, and they deploy it more actively.

JUST KEEPING UP APPEARANCES? MERITOCRACY IN SCIENCE

Science, like sport, is considered to be a meritocracy - you get where you are because of your abilities. Other factors such as mentors, social skills and appearance have a role to play, but if the central ability is not there, then one would not expect those other factors to carry someone so far.

But there are clearly problems with the representation of women in science - evidence shows that both men and women undervalue women's abilities and achievements (and not just in science). This is not helped when articles in the press seem to support a basic fallacy that men and women find different issues interesting to study, and study them in different ways.

This is probably best illustrated by an interview with Baroness Greenfield, who was for 12 years director of the Royal Institution, that appeared in The Times in the wake of her (now resolved) dispute with the organisation.

I wasn't surprised by the writer going on at some length about Greenfield's clothes. While this is irritating, it is scarcely unfamiliar territory. It is generally hard to read an article about female scientists that doesn't mention their appearance. So one approaches a profile of Greenfield with the weary expectation that it will refer to her outfits and her demeanour in a way that an interview with Richard Dawkins would not.

And Greenfield doesn't necessarily deflect this interest: in the Times interview she was quoted as saying that "scientists are expected to be 'dowdy'". If this is true, perhaps it is truly newsworthy if a female scientist rocks up in a miniskirt.

But does this picture of a colourful scientific bird of paradise, flitting out from a horde of dowdy female colleagues - stomping around in tweed, stroking their wiry chins and rummaging through their mops of grey hair for lost test tubes (or whatever else dowdy is supposed to connote, and I quite like the sound of it now) - reflect an actual truth? Maybe female scientists can be as dowdy or as miniskirt-wearing as they like (or even find a way to dress that is in between the two extremes). Furthermore, maybe how they dress has no appreciable effect on the quality of their science.

However depressing I find this, it is not what was truly upsetting about this interview. As long as general standards of public decency are observed, I don't think it's my place to criticise or make assumptions about how my colleagues dress.

But the interview went on to suggest that Greenfield's research was "feminine". Greenfield is a pharmacologist - how is that feminine? The article clarified: "It's Facebook and Grand Theft Auto rather than physics and the Large Hadron Collider", referring to Greenfield's many comments on the effects of computer games and social networking.

I think it is misleading to describe (for example) research into social networking as "feminine" and researching physics as "masculine". If the suggestion is that only women study the former and only men the latter, then this is simply incorrect.

From my own experience, I know of very interesting research into how people coordinate conversations in chat rooms that is carried out by a man, and University College London's physics department has research-active female faculty members.

And if the sense is a wider one, that somehow researching physics is inherently male and better suited to a male mindset, then I think this misses the point that science is defined by how we approach our area of study, not what that area of study is.

For example, Greenfield says it's hard to get girls to go into science because girls "want to know about relationships". Even if that's true, then psychology is a science, and a popular one, in which human relationships and behaviour can be studied.

To develop this theme, something that seems to crop up in interviews with Greenfield, maybe often at the interviewer's behest, is the idea that somehow men and women have different approaches to science, that women "do" science differently from men.

I find this most worrying of all - it can't help people to take female scientists seriously if the nature of their actual scientific enterprise is called into question. Greenfield herself does not always make this clear. She is quoted as saying: "I came from the arts, but I love the way that science is absolutely ruthless, saying 'Where is the evidence - prove it'." Later in the same interview, she says: "With science, data is everything. You define yourself and your values not by your salary or glamour but by the fact that you are the expert in this area and you can trump someone else. It's a very male mindset; it's very competitive." So, science is great when it is evidence-based and ruthless, but it's not great when it's data-based, competitive and (apparently) pretty male.

I have to declare an interest - I am a woman, a scientist and a professor, and I once really made my physics teacher (a woman) laugh by suggesting that I wanted to be an astrophysicist. Being a scientist is the best job in the world - I still can't believe that I get to do this for a living. I am delighted when we get scientists in the media discussing their work and helping people to engage with science. I like it even more if we get a good discussion of good science in the media. In my experience, most people are fascinated by science, and a high profile for science means more potential scientists, and that's good for us all.

But as a female scientist, it pains me that one of the UK's foremost female scientists is not better known for her actual science.

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Sophie Scott is professor at the Institute of Cognitive Neuroscience, University College London.