GUY RAZ, HOST:
Let's talk about this for a sec - why do you guys say maths?
HANNAH FRY: Well, this is like, a massive issue.
RAZ: It's a big issue.
FRY: People get really properly angry about it. There is a kind of joke in the U.K. where people say math and then someone just goes (makes S sound).
RAZ: This is Hannah Fry. She's a maths-matician.
FRY: As far as I'm concerned, I struggle to find anything in the world that you can't get an interesting perspective on by using maths.
RAZ: Including perhaps the most mysterious, inexplicable part of life, which is of course love. Do you think that there's a connection between math and love? Like, it can explain love, in part?
FRY: Well, so the thing is, is that in people's love lives, as in all of life, there are certain patterns in the way that people behave. And maths is perfectly placed to be able to take those patterns and translate them, and then give them back to you with a little bit of insight wrapped up.
RAZ: That's so romantic.
FRY: (Laughter). All right, good point.
RAZ: Hannah has written about this in a book called "The Mathematics Of Love," and it's full of lessons about how numbers can actually help us find love, including...
(SOUNDBITE OF TED TALK)
FRY: How to win at online dating.
RAZ: Here's Hannah's Ted Talk.
(SOUNDBITE OF TED TALK)
FRY: OK. 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. Let me show you how this works. OK so, 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. And the important thing to note 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 idea is that if you're looking through people's profiles on OKCupid and you find someone, and they're super, super beautiful, in your head you're thinking they probably get loads of messages, there's not really much point in me humiliating myself by sending them a message, they're never going to reply. And you move on to the next profile. But then you see someone and you think they're really beautiful, but you also think that perhaps not everyone is going to think that they're beautiful. So, maybe they've got loads of tattoos or a crazy color hair or whatever. In that way, it's sort of less competition for you and it's an extra incentive for you to get in touch.
RAZ: OK. All right, so, if you want to get like, more attention and like, more messages to you, you want to play up the things that make you like, a little weird or different, right?
FRY: Yeah because the people who like you anyway are still going to like you, and the people who don't only serve to your advantage.
RAZ: So, in some ways you could argue that mathematicians like, have an unfair advantage when it comes to online dating?
FRY: (Laughter) Yeah. I mean, mathematicians are famously brilliant at finding lovers.
RAZ: Are they really?
FRY: Yeah. Oh, yeah, oh, yeah.
RAZ: Really? Who knew?
FRY: (Laughter) I'm joking.
(SOUNDBITE OF TED TALK)
FRY: 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 chances of long-term happiness. So the question is then, how do you know when is the right time to settle down, given all the people that you could date in your lifetime? Now, thankfully there's a rather delicious bit of mathematics that we can use to help us out here called optimal stopping theory. OK 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 of course in your lifetime, and they'll be at kind of 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've had. And equally, you can't go back and change your mind. OK 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.
RAZ: Hannah says using this idea from math, it's called optimal stopping theory, can dramatically increase your odds of finding the perfect partner. So, say you dated like, 20 people in your life. Well, if you just picked one of those 20 people at random to marry, there's a 5 percent chance you'd have found your perfect partner.
FRY: Which is like, not very good odds, really.
RAZ: But, if you dated the same 20 people and you flat-out rejected the first third?
FRY: You then can up your chances of finding the perfect person to almost 40 percent.
FRY: So, from going from 1 in 20 to more than a third, you've just massively changed your chances of finding them.
RAZ: But, this is all a matter of probability. There's a chance you could reject your soul mate in that 37 percent window.
FRY: Yeah, I mean there are risks involved, right? So, your perfect person could come along in your rejection phase and you could get rid of them and then spend the rest of your life regretting the fact that you didn't just marry them. This only maximizes your chances of finding the perfect person for you, it doesn't guarantee it.
RAZ: Ah - math.
FRY: Yeah, [expletive].
RAZ: It ruins everything.
FRY: (Laughter) I think it makes everything brilliant.
RAZ: OK. So, let's say you've made it through your rejection phase, found that perfect person within your 37 percent window. How do you know if it's going to last?
FRY: And that's something that, it turns out, you can write a really beautifully simple set of equations to look at.
RAZ: Beautifully simple if you're a mathematician.
FRY: So the equation is W T plus one equals little W plus R W W T, plus I H M brackets H T.
RAZ: Mathematicians came up with this equation for love by studying how couples argue. A group of psychologists spent years filming couples having conversations.
FRY: And the asked them, for 15 minutes or so, I want you to talk about the most contentious issue in your relationship.
RAZ: Things like who does what around the house, working late, missing important events, money, in-laws. And during those conversations, the researchers monitored the couples' heart rates, their facial expressions, how much they were sweating.
FRY: And they worked out a way to give them scores - so positive or negative scores based on everything that happened in their interaction.
RAZ: And then those numbers, they got plugged into the set of equations Hannah just mentioned.
FRY: We call it a coupled set of equations because you have one equation for the husband and one equation for the wife.
RAZ: So for the wife, better known as...
FRY: W, T plus 1.
RAZ: How she will handle talking about a contentious issue with her husband is based on...
FRY: Her general mood, little W, plus her general mood when she's with her husband, R W W T, plus how she reacts to the last thing that her husband says in that exact conversion, I H M brackets H T.
RAZ: With this information, and a lot of calculations...
FRY: They could predict whether or not people are going to get divorced with a 90 percent accuracy.
RAZ: Wow, how do you know?
FRY: So, there's a few things that are really big indicators, and these are patterns that only come out when you look at this mathematically. It's not just about - because everybody - every couple argue, right? Every couple are a little bit negative to each other at some point, but it's about how that negativity can spiral into something really out of control and about how likely that is to happen.
(SOUNDBITE OF TED TALK)
FRY: For the really important term in this equation is the influence that people have on one another, 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 getting really [expletive] off, mostly, and vice versa. Now, I always thought that good marriages were about compromise and understanding and allowing the person to have space to be themselves. So I would've 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. 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.
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RAZ: This is very reassuring to know. That's pretty cool that, you know, with an equation, you can just predict if you're destined for a life of bliss.
FRY: Well, maybe that's not quite true. It's more like, these equations give us a language to be able to talk about conflict in long-term relationships in a way that you can't do if you just think really qualitatively.
RAZ: Yeah, I mean, most people don't think of math as a language, right?
FRY: No, I know. And it just absolutely is. And so Galileo says that - talks about the universe as though it's a book that's been written by God, and everything in the universe is contained within this book. And then he says that the language of that book has to be mathematics. And it's just absolutely true. You can just describe everything around you, everything in the human world, everything in the natural world, everything in the physical world. At some level, you can use math to describe it.
RAZ: Hannah Fry - her TED Book about this is called "The Mathematics Of Love." You can find out more about the book and see Hannah's full talk at ted.com.
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