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. (Laughter) 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 UK, 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. (Laughter) 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. (Laughter) OK, 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. (Laughter) 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 one and five. 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 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 … (Laughter) seem to think that she looks

a bit like a horse. (Laughter) Now, I think that if you ask people

how attractive they thought Jessica Parker or Portia de Rossi were, and you ask them to give

them a score between one and five 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 four 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

to make 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? But 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, (Laughter) 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. OK, 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? (Laughter) 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 … (Laughter) nibbling at your remains. OK, 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. That’s OK, because

you’re in your rejection phase, so that’s fine, you can reject them. But then imagine

the next person to come along is just marginally less boring,

dull and terrible … (Laughter) than everybody that you’ve seen before. Now, if you are following the maths,

I’m afraid you have to marry them … (Laughter) 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.” (Laughter) It’s actually more romantic

than I normally manage. (Laughter) OK, 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, we do sort of do this anyway. We 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. OK, so that was Top Tip #2. Now, Top Tip #3: How to avoid divorce. OK, 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? (Laughter) But it’s a sad fact of modern life that one in two 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. Whereas bad relationships, by which I mean,

probably going to get divorced, they found themselves getting

into a spiral of negativity. Now just by using these very simple ideas, Gottman and his group were able to predict whether a given couple

was going to get divorced with a 90 percent accuracy. But it wasn’t until he teamed up

with a mathematician, James Murray, that they really started to understand what causes these negativity spirals

and how they occur. And the results that they found, I think, are just incredibly

impressively simple and interesting. So these equations predict how the wife

or husband is going to respond in their next turn of the conversation, how positive or negative

they’re going to be. And these equations depend on the mood of the person

when they’re on their own, the mood of the person when

they’re with their partner, but most importantly, they depend on how much the husband and wife

influence one another. Now, I think it’s important

to point out at this stage, that these exact equations

have also been shown to be perfectly able at describing what happens between two countries

in an arms race. (Laughter) So that an arguing couple

spiraling into negativity and teetering on the brink of divorce is actually mathematically equivalent

to the beginning of a nuclear war. (Laughter) But the really important term

in this equation is the influence that people

have on one another, and in particular, something called

“the negativity threshold.” Now, the negativity threshold, you can think of as

how annoying the husband can be before the wife starts to get

really pissed off, and vice versa. Now, I always thought that good marriages

were about compromise and understanding and allowing the person

to have the space to be themselves. So I would have thought that perhaps

the most successful relationships were ones where there was

a really high negativity threshold. Where couples let things go and only brought things up

if they really were a big deal. But actually, the mathematics

and subsequent findings by the team have shown the exact opposite is true. The best couples,

or the most successful couples, are the ones with a really low

negativity threshold. These are the couples

that don’t let anything go unnoticed and allow each other

some room to complain. These are the couples that are continually

trying to repair their own relationship, that have a much more positive

outlook on their marriage. Couples that don’t let things go and couples that don’t let trivial things

end up being a really big deal. Now of course, it takes a bit more

than just a low negativity threshold and not compromising

to have a successful relationship. But I think that it’s quite interesting to know that there is really

mathematical evidence to say that you should never

let the sun go down on your anger. So those are my top three tips of how maths can help you

with love and relationships. But I hope, that aside from

their use as tips, they also give you a little bit of insight

into the power of mathematics. Because for me, equations

and symbols aren’t just a thing. They’re a voice that speaks out

about the incredible richness of nature and the startling simplicity in the patterns that twist and turn

and warp and evolve all around us, from how the world works to how we behave. So I hope that perhaps,

for just a couple of you, a little bit of insight

into the mathematics of love can persuade you to have

a little bit more love for mathematics. Thank you. (Applause)

She’s awesome

"is math science?"

Well I have run the numbers, done the math, solved the equations…..the answer is quite simply, mathematically she would be a suitable mate for me….

SJP can look very good, but horse face at other times. Over all Portia is better looking to me.

Of course personality is crucial, a lesser attractive face with a killer personality is better than the reverse. Also a killer rack with lesser face is better than a killer face and raisins on a board

My eyes lighted up when I saw her lmao, instaclick

Before I begin playing this video: Solving basic and advanced algebra equations kept my brain running! Math could have been frustrating, but I thoroughly enjoyed the heck out of it. I got smarter like that, like how people get stronger after doing muscle workouts at the gym.

Are people commenting about nobody laughibg deaf? Yes – And stupid enough to comment about it.

I already fell in love: Hannah Fry 🤗

But the question is. How do you know how many people you date so i can get the 37%. If i count 100, ill die before i get to my 38th date. If i count toward my expectations, i think i already dated 99% (3 lol). The math is wrong.

Finding love is easy. Just type in Hannah Fry on youtube.

So I'm a fish that is going to die alone.

shoot for the stars! so that when you miss you fall back down to where you started lol

"somebody with a university degree" , immediately 95% of people fall off lol

When you’re so single you can mathematically describe singleness

She is amazing.

Really well put together presentation. Thanks Hannah

Your like MATH, you keepfinding x

Mathematics for love for women, men with nice car, big house, good income and so on.

How did anybody get me interested in mathematics??? Great job!!!

Sarah Jessica Parker is almost one of the most beautiful people…….. wtf………………………..

since people don't know how many future dates could be – is time an approximation? i.e.here 15+ (35-15)+0,37 = 22,4 years old = optimal stopping date? (PS: The Valentine Card at 10:30 is wrong. It must read: "less terrible than ALL I dated (before)" or "less terrible than the first 37% in MY DATING Window" or "of my Dating POOL (= dated before + would have dated later.)"