Placeholder Image

Subtitles section Play video

  • Today I want to talk to you about the mathematics of love.

  • Now, I think that we can all agree

  • that mathematicians are famously excellent at finding love.

  • But it's not just because of our dashing personalities,

  • superior conversational skills and excellent pencil cases.

  • It's also because we've actually done an awful lot of work into the maths

  • of how to find the perfect partner.

  • Now, in my favorite paper on the subject, which is entitled,

  • "Why I Don't Have a Girlfriend" -- (Laughter) --

  • Peter Backus tries to rate his chances of finding love.

  • Now, Peter's not a very greedy man.

  • Of all of the available women in the U.K.,

  • all Peter's looking for is somebody who lives near him,

  • somebody in the right age range,

  • somebody with a university degree,

  • somebody he's likely to get on well with,

  • somebody who's likely to be attractive,

  • somebody who's likely to find him attractive.

  • (Laughter)

  • And comes up with an estimate of 26 women in the whole of the UK.

  • It's not looking very good, is it Peter?

  • Now, just to put that into perspective,

  • that's about 400 times fewer than the best estimates

  • of how many intelligent extraterrestrial life forms there are.

  • And it also gives Peter a 1 in 285,000 chance

  • of bumping into any one of these special ladies

  • on a given night out.

  • I'd like to think that's why mathematicians

  • don't really bother going on nights out anymore.

  • The thing is that I personally

  • don't subscribe to such a pessimistic view.

  • Because I know, just as well as all of you do,

  • that love doesn't really work like that.

  • Human emotion isn't neatly ordered and rational and easily predictable.

  • But I also know that that doesn't mean

  • that mathematics hasn't got something that it can offer us

  • because, love, as with most of life, is full of patterns

  • and mathematics is, ultimately, all about the study of patterns.

  • Patterns from predicting the weather to the fluctuations in the stock market,

  • to the movement of the planets or the growth of cities.

  • And if we're being honest, none of those things

  • are exactly neatly ordered and easily predictable, either.

  • Because I believe that mathematics is so powerful that it has the potential

  • to offer us a new way of looking at almost anything.

  • Even something as mysterious as love.

  • And so, to try to persuade you

  • of how totally amazing, excellent and relevant mathematics is,

  • I want to give you my top three mathematically verifiable tips for love.

  • Okay, so Top Tip #1:

  • How to win at online dating.

  • So my favorite online dating website is OkCupid,

  • not least because it was started by a group of mathematicians.

  • Now, because they're mathematicians,

  • they have been collecting data

  • on everybody who uses their site for almost a decade.

  • And they've been trying to search for patterns

  • in the way that we talk about ourselves

  • and the way that we interact with each other

  • on an online dating website.

  • And they've come up with some seriously interesting findings.

  • But my particular favorite

  • is that it turns out that on an online dating website,

  • how attractive you are does not dictate how popular you are,

  • and actually, having people think that you're ugly

  • can work to your advantage.

  • Let me show you how this works.

  • In a thankfully voluntary section of OkCupid,

  • you are allowed to rate how attractive you think people are

  • on a scale between 1 and 5.

  • Now, if we compare this score, the average score,

  • to how many messages a selection of people receive,

  • you can begin to get a sense

  • of how attractiveness links to popularity on an online dating website.

  • This is the graph that the OkCupid guys have come up with.

  • And the important thing to notice is that it's not totally true

  • that the more attractive you are, the more messages you get.

  • But the question arises then of what is it about people up here

  • who are so much more popular than people down here,

  • even though they have the same score of attractiveness?

  • And the reason why is that it's not just straightforward looks that are important.

  • So let me try to illustrate their findings with an example.

  • So if you take someone like Portia de Rossi, for example,

  • everybody agrees that Portia de Rossi is a very beautiful woman.

  • Nobody thinks that she's ugly, but she's not a supermodel, either.

  • If you compare Portia de Rossi to someone like Sarah Jessica Parker,

  • now, a lot of people, myself included, I should say,

  • think that Sarah Jessica Parker is seriously fabulous

  • and possibly one of the most beautiful creatures

  • to have ever have walked on the face of the Earth.

  • But some other people, i.e., most of the Internet,

  • seem to think that she looks a bit like a horse. (Laughter)

  • Now, I think that if you ask people how attractive they thought

  • Sarah Jessica Parker or Portia de Rossi were,

  • and you ask them to give them a score between 1 and 5,

  • I reckon that they'd average out to have roughly the same score.

  • But the way that people would vote would be very different.

  • So Portia's scores would all be clustered around the 4

  • because everybody agrees that she's very beautiful,

  • whereas Sarah Jessica Parker completely divides opinion.

  • There'd be a huge spread in her scores.

  • And actually it's this spread that counts.

  • It's this spread that makes you more popular

  • on an online Internet dating website.

  • So what that means then

  • is that if some people think that you're attractive,

  • you're actually better off

  • having some other people think that you're a massive minger.

  • That's much better than everybody just thinking

  • that you're the cute girl next door.

  • Now, I think this begins makes a bit more sense

  • when you think in terms of the people who are sending these messages.

  • So let's say that you think somebody's attractive,

  • but you suspect that other people won't necessarily be that interested.

  • That means there's less competition for you

  • and it's an extra incentive for you to get in touch.

  • Whereas compare that to if you think somebody is attractive

  • but you suspect that everybody is going to think they're attractive.

  • Well, why would you bother humiliating yourself, let's be honest?

  • Here's where the really interesting part comes.

  • Because when people choose the pictures that they use on an online dating website,

  • they often try to minimize the things

  • that they think some people will find unattractive.

  • The classic example is people who are, perhaps, a little bit overweight

  • deliberately choosing a very cropped photo,

  • or bald men, for example,

  • deliberately choosing pictures where they're wearing hats.

  • But actually this is the opposite of what you should do

  • if you want to be successful.

  • You should really, instead, play up to whatever it is that makes you different,

  • even if you think that some people will find it unattractive.

  • Because the people who fancy you are just going to fancy you anyway,

  • and the unimportant losers who don't, well, they only play up to your advantage.

  • Okay, Top Tip #2: How to pick the perfect partner.

  • So let's imagine then that you're a roaring success

  • on the dating scene.

  • But the question arises of how do you then convert that success

  • into longer-term happiness and in particular,

  • how do you decide when is the right time to settle down?

  • Now generally, it's not advisable to just cash in

  • and marry the first person who comes along

  • and shows you any interest at all.

  • But, equally, you don't really want to leave it too long

  • if you want to maximize your chance of long-term happiness.

  • As my favorite author, Jane Austen, puts it,

  • "An unmarried woman of seven and twenty

  • can never hope to feel or inspire affection again."

  • (Laughter)

  • Thanks a lot, Jane. What do you know about love?

  • So the question is then,

  • how do you know when is the right time to settle down

  • given all the people that you can date in your lifetime?

  • Thankfully, there's a rather delicious bit of mathematics that we can use

  • to help us out here, called optimal stopping theory.

  • So let's imagine then,

  • that you start dating when you're 15

  • and ideally, you'd like to be married by the time that you're 35.

  • And there's a number of people

  • that you could potentially date across your lifetime,

  • and they'll be at varying levels of goodness.

  • Now the rules are that once you cash in and get married,

  • you can't look ahead to see what you could have had,

  • and equally, you can't go back and change your mind.

  • In my experience at least,

  • I find that typically people don't much like being recalled

  • years after being passed up for somebody else, or that's just me.

  • So the math says then that what you should do

  • in the first 37 percent of your dating window,

  • you should just reject everybody as serious marriage potential.

  • (Laughter)

  • And then, you should pick the next person that comes along

  • that is better than everybody that you've seen before.

  • So here's the example.

  • Now if you do this, it can be mathematically proven, in fact,

  • that this is the best possible way

  • of maximizing your chances of finding the perfect partner.

  • Now unfortunately, I have to tell you that this method does come with some risks.

  • For instance, imagine if your perfect partner appeared

  • during your first 37 percent.

  • Now, unfortunately, you'd have to reject them.

  • (Laughter)

  • Now, if you're following the maths,

  • I'm afraid no one else comes along

  • that's better than anyone you've seen before,

  • so you have to go on rejecting everyone and die alone.

  • (Laughter)

  • Probably surrounded by cats nibbling at your remains.

  • Okay, another risk is, let's imagine, instead,

  • that the first people that you dated in your first 37 percent

  • are just incredibly dull, boring, terrible people.

  • Now, that's okay, because you're in your rejection phase,

  • so thats fine, you can reject them.

  • But then imagine, the next person to come along

  • is just marginally less boring, dull and terrible

  • than everybody that you've seen before.

  • Now, if you are following the maths, I'm afraid you have to marry them

  • and end up in a relationship which is, frankly, suboptimal.

  • Sorry about that.

  • But I do think that there's an opportunity here

  • for Hallmark to cash in on and really cater for this market.

  • A Valentine's Day card like this. (Laughter)

  • "My darling husband, you are marginally less terrible

  • than the first 37 percent of people I dated."

  • It's actually more romantic than I normally manage.

  • Okay, so this method doesn't give you a 100 percent success rate,

  • but there's no other possible strategy that can do any better.

  • And actually, in the wild, there are certain types

  • of fish which follow and employ this exact strategy.

  • So they reject every possible suitor that turns up

  • in the first 37 percent of the mating season,

  • and then they pick the next fish that comes along after that window

  • that's, I don't know, bigger and burlier

  • than all of the fish that they've seen before.

  • I also think that subconsciously, humans, or we do sort of do this anyway.

  • We have to give ourselves a little bit of time to play the field,

  • get a feel for the marketplace or whatever when we're young.

  • And then we only start looking seriously at potential marriage candidates

  • once we hit our mid-to-late 20s.

  • I think this is conclusive proof, if ever it were needed,

  • that everybody's brains are prewired to be just a little bit mathematical.

  • Okay, so that was Top Tip #2.

  • Now, Top Tip #3: How to avoid divorce.

  • Okay, so let's imagine then that you picked your perfect partner

  • and you're settling into a lifelong relationship with them.

  • Now, I like to think that everybody would ideally like to avoid divorce,

  • apart from, I don't know, Piers Morgan's wife, maybe?

  • But it's a sad fact of modern life

  • that 1 in 2 marriages in the States ends in divorce,

  • with the rest of the world not being far behind.

  • Now, you can be forgiven, perhaps

  • for thinking that the arguments that precede a marital breakup

  • are not an ideal candidate for mathematical investigation.

  • For one thing, it's very hard to know

  • what you should be measuring or what you should be quantifying.

  • But this didn't stop a psychologist, John Gottman, who did exactly that.

  • Gottman observed hundreds of couples having a conversation

  • and recorded, well, everything you can think of.

  • So he recorded what was said in the conversation,

  • he recorded their skin conductivity,

  • he recorded their facial expressions,

  • their heart rates, their blood pressure,

  • basically everything apart from whether or not the wife was actually always right,

  • which incidentally she totally is.

  • But what Gottman and his team found

  • was that one of the most important predictors

  • for whether or not a couple is going to get divorced

  • was how positive or negative each partner was being in the conversation.

  • Now, couples that were very low-risk

  • scored a lot more positive points on Gottman's scale than negative.