Sex is a simple equation

October 5, 2004

Independent News & media (UK)

Looking for a perfect lover? Mathematics could be the answer. Catherine Townsend meets a woman who believes in a link between numbers and orgasms.
05 October 2004

Most women's idea of a scientific approach to love does not extend beyond the horoscope pages. But a mathematician, Clio Cresswell PhD, believes the answers to some of the big questions lie in mind-bending equations. After years of research, she is explaining her theories on finding the perfect relationship in her new book, Mathematics and Sex.

"Mathematics is all about patterns, whether it's in the stock-market, society or in your bedroom," she says. Despite her day job as a lecturer at the University of South Wales, the 30-year-old's quirky humour and unconventional life are more reminiscent of a Sex and the City character than a stuffy academic. She combines her research and teaching with writing an advice column in a women's magazine and speaking engagements worldwide.

But Dr Cresswell got the idea to apply maths to romance by accident. "I came across these fascinating equations that used maths to figure out how much one should compromise in a marriage, and was blown away by how many people asked about them," she says. She explains that the psychologists John Gottman and Catherine Swanson watched newly-wed couples interact for 15 minutes, and observed their reaction to each other to determine the likelihood of their staying together. The results, she says, were surprising, and "have had a big impact on how psychologists view marital theory." They found that, while some people expressed negativity as soon as they felt it, others held their anger in and "empathised" for as long as possible with their mates.

She adds: "We have always heard in the past that empathy is the best method, but they found that people who hold in their anger and rationalise their partner's behaviour by saying something like 'Oh, it's OK that he didn't put the cap back on the toothpaste, because he had a hard childhood' are much more likely to get divorced than those who get their anger out there and then. People who get out the negativity straight away do better because they have higher standards, and see themselves as fighting for their marriages. When members of the couple keep giving in, then they are lowering their standards."

Moving on, Cresswell explains how maths can help in hunting for a partner. "It's an interesting problem because divorce rates are getting higher and higher. If you bought a DVD player that someone told you had a 50 per cent chance of breaking down, you would ask your friends what they do and take advice," she explains. "But with love we don't want to be unromantic, so we say 'No, I'll know when I find The One,' which is completely counter-intuitive."

In fact, she questions the belief that there is "one" at all: "The maths suggests that there are multiple people you could be happy with, and the idea of a soulmate is disputed if you look at social Darwinistic theory," she says, laughing. "But it's tough to dispute, because, hey, we've all watched Pretty Woman."

For those searching for a soulmate by pulling in bars, Cresswell moves on to the "rule of 12 bonks", which she calls "my personal favourite". "The idea is, you need to date 12 people, then after you get to 12 you continue testing. But you take the next best partner that comes along, whether that is number 13 or 40." Cresswell adds that the notion of using this figure to determine how many partners to sample before seriously searching for "the one" came out of a German study aimed at addressing relationship issues, including the high divorce rate. "The study found that doing this will give you a 75 per cent chance of success in finding the person with the qualities you want."

But the rule does not have to be applied literally. "You don't have to sleep with them, if that is against your personal beliefs. But I'm a modern woman, and I have to say that I did want to bonk my 12."

And the anecdotal women who marry high-school sweethearts? "Actually, they may be on to something because if you shrink the sample size down to a very small space, choosing your first love makes sense," she says. "So we're not all acting irrationally, just using what evolution has taught us."

While comparing relationships to the stock-market may seem like an alien concept, Cresswell insists that applying maths to love is a natural evolution. "The Eighties was the first time that mathematical models got applied to the stock-market, and now everyone's doing it," she says. "Basically, you choose symbols based on particular characteristics and see how they develop, and how the relationship will grow or decline, like the rise and fall of the money market."

According to Cresswell, relationships and romance are nothing more than a dynamic weave of different possibilities being played out, meaning that maths can be used to used to simulate conditions within a relationship - or an orgasm. "I saw a mathematical study that looked at how to compare orgasms between men and women," she says. "Basically, women's orgasms have kind of been studied to death in terms of their emotional connection, and men's from the physical side only. In this case, researchers looked at a bunch of words that could describe an orgasm, then got people to evaluate each word for feeling - fun, exciting, pleasurable, and so on. They did a statistical analysis and found that men and women basically picked the same descriptions of what it felt like."

Cresswell also discusses how dating services work, and why both men and women are happier if they actively proposition as many desirable partners as possible. She admits to using the equations as a tool for her own love life, especially in understanding the ups and downs. "Psychologists and sociologists are studying love, but no one really knows what it is, except that it can be an unpleasant feeling that is like an emotional washing machine," she says. "But for some people the turmoil settles down into companionship, while for others it doesn't. So we use equations to predict who will fall into these types of tempestuous relationships. Maths helped me deal objectively with the anxiety, self-doubt and nervousness - and to remind myself I'm just going to have to get through it."

But for the moment she is loving being free and single. "I'm one of these thoroughly modern women who does not feel the need for a commitment at this point," she says.

She hopes that more people will see that the juxtaposition of maths and love is not all that strange. "Like using art, poetry and music to communicate," she says, "maths is just another way to connect to the world."

Clio Cresswell's book 'Mathematics and Sex' will be published in the UK early next year



Sleep with 12 people. If you then take the next best person who comes along, whether they are number 13 or number 113, you have a 75 per cent chance of having a lasting relationship. Then again, if you're on number 113, you may have done too much research.


There is an inverse relationship between empathy and future happiness with a partner. Studies on newly-weds revealed that those who are quickest to voice their annoyance are much more likely to be together six years down the road than their teeth-gritting counterparts. So, if he farts in his sleep, tell him.


The Cornwell mathematician Steven Strogatz formulated the evolution of Romeo and Juliet's love affair, showing how Romeo's love depends on Juliet's responses, and vice versa. Put simply, new love is always a rollercoaster: get used to it.


Dusting off the chat-up lines and polishing up the charm may be worth it for your long-term prospects of happiness. This rule states that a serious effort at propositioning as many people as possible reaps dividends. More attempts yield more results, but the attempts themselves help you to come to a better idea of your perfect partner.


There's no perfect partner out there, so stop looking for "the one". The formula is derived from Darwinian theory, and proves that there are multiple partners with whom we could be equally happy. You need to stop hanging on for the Brad Pitt lookalike with a six-figure income and a heart of gold, as this approach is both unhelpful and statistically unlikely to occur. Unlikely, though not impossible...

Ed Caesar



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