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More or Less
The mathematical secrets to relationships
00:09:36
How maths can help you find love, and hold on to it. Plus, we hear a collection of our...
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- [00:00]
Ruth Alexander
This is the short edition of More or Less, first broadcast on the BBC World Service.
- [00:06]
BBC Announcer
Thank you for downloading from the BBC. For details of our complete range of podcasts and our terms of use, go to bbcworldservice.com podcasts
- [00:20]
Ruth Alexander
hello and welcome to More or Less on the BBC World Service. I'm Ruth Alexander. Numbers can be so powerful. They can show you the world in a new light, move you to tears and even make you laugh. And I hope you might experience that in a few minutes time when we hear a collection of our listeners much loved statistics. But first, let's dwell on the sexy side of statistics. In celebration of Valentine's Day, Tim Harford has asked Hannah Fry, the author of a new book, the Mathematics of Love, to give him an example of hound numbers could improve our love lives.
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Hannah Fry
Online dating is kind of the gift that keeps giving if you are a mathematician or a statistician, because it's the first time.
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Tim Harford
No, because you can finally get a boyfriend or girlfriend or because it gives you data.
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Hannah Fry
Mathematicians are famously excellent at finding lovers, of course, but it's the first time really that we've been able to look at the way that people talk about themselves when they're looking for love and also how they interact with other people. There are some actually quite interesting findings. There's a book by Christian Rudder, who was the founder of OkCupid and also a math major at college. So he's kind of come up with all sorts of different ways to look at the data from his website. It turns out that how attractive you are doesn't necessarily dictate how popular you are on an online dating website. It's actually much more about how much you divide opinion that matters. So the people who have tattoos, for example, tend to do really, really well on Internet dating websites. In fact, the person who's the most messaged person on all of OkCupid is a new York girl who's got that kind of 50s style and lots of tattoos all over. But really div opinion, that's much more important than just being beautiful.
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Tim Harford
So the idea is there that you need to also be interesting. And one way of measuring interestingness is if a lot of people don't like the way you look and a lot of people do like the way you look, you must look interesting. So that's online dating. What other mathematical applications could we find that will help us find love or help us understand love?
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Hannah Fry
Yeah, well, so probably one of my favourite examples from the book is a mathematical argument to say that you should always be the person who approaches people at a party. I know that when I was single I would sort of sit back and I'd let people come to me. But the thing is that you can show mathematically that to do that you'll always end up much worse off than if you're the person doing the approaching, however difficult it is to do so. It's called the stable marriage problem.
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Tim Harford
The Gail Shapley algorithm. Algorithm, which won a Nobel Prize for economics recently, sort of influenced the way that kidneys get dished out these days. But that's perhaps not quite so romantic.
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Hannah Fry
Yes, perhaps not.
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Tim Harford
So explain the algorithm.
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Hannah Fry
So imagine that you have a group of boys and girls at a party. It's a bit easier if you have two groups who are just targeting each other. If the boys do all of the approaching, they have sort of an ordered list in their heads of who they prefer out of all of the girls, right? So what they do is they'll start at the top of their list and then if they get rejected, they'll work their way down. Whereas the girls, on the other hand, who are standing back and letting the boys approach them, they'll end up with the least bad person that approaches them, which in comparison to the boys who get the best girl who'll have them. So you can prove this mathematically, that if you're in the group that does the approaching, you're always better off.
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Tim Harford
Now, Hannah, I have to ask, have you ever sneakily or otherwise deployed mathematics to get your own way romantically?
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Hannah Fry
Well, perhaps not to find love. Although since researching this book, there was a study in America that I've come across which is using mathematics to look at marriage and to look at long term relationships and compromise and things like that. And there's a really amazing result that came out because you can actually use a mathematical model. You can use equations to look at how couples interact with each other. So it's John Gothard and James Murray, and using these mathematics, they can predict whether or not a couple get divorced with 90% accuracy, which is extraordinary. But the real thing that came out is about how you compromise and how you approach arguments within a long term relationship. So when I was growing up, I always thought that the best relationships are the ones where you always wanting to compromise, give the other person, you know, lots of room to be themselves and this and the other. But actually the best relationships are sort of the opposite. It's the ones where people are continually repairing very small issues and allow each other room to complain. Those are the relationships that end up doing much better because things don't end up spiraling out of control. So having known about that in my own relationships, not just, you know, with my husband, but with other people, I have had that at the back of my mind now.
- [04:53]
Ruth Alexander
Hannah Fry, Maths Lecturer at University College London. Unlike so many UCL maths lecturers, a goddess of love. She was talking to Tim Harford and you can talk to us via our email address more or lessbc.co.uk we love getting your questions and comments and we've been rummaging around in our inbox to put together a collection of your favourite statistics. So here are our favourites of your favourites.
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Nick
My Favourite Statistic 85% of 84.2% 97%
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Kevin
of all statistics are made up Favourite
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Nick
Statistic 100% of people who say x percent of statistics are made up think they are clever, funny and original.
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Nicola
The average number of legs on a person is less than 2.
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Kevin
I like it because it seems to
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Nicola
be patently true, obviously incorrect and practically
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Kevin
useless all at the same time.
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Nicola
My favorite statistic is Bayes Law. I use it to manage my mental health all the time and every parent with teenage children needs to know it. The probability something terrible happens to teenagers when they go out One in a million, I hope. The probability they forget to call or lose their phone 1 in 10. So if they've not called, the probability of something terrible having happened is 1 in 100,000. I've used it so much that when we get cross with my daughter for forgetting to call, she simply says baes. However, it only goes so far. If they've not called the next morning, statistical rationality goes out of the window and panic takes over.
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Nick
Mine is the tfr, the total fertility rate of a population. This statistic allows us to make predictions about the social and economic behavior of the population related to how long ago the TFR of the population fell from above four to a much lower number. This has now happened in almost all human populations. In the case of Britain it was in the late 19th century. In the case of Iran it was during the 1980s. China's decline began in the 1960s. Once their TFR falls, populations enjoy what is known as a demographic dividend. GDP per capita has to begin to rise because there are fewer unproductive children relative to productive adults. Also, women are more likely to be employed in salaried work than in caring for children. And there is so much more. I can go on and on about my enthusiasm for tfr.
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Kevin
I am a psychiatrist in training. My favourite statistic to mention although a terribly Sad1 is 15 to 20 years. And it's the number of years your life expectancy is on average reduced if you have schizophrenia. It has become my favorite statistic to mention because it illustrates the reality of the disadvantage that faces the one in every hundred of us that lives with this most stigmatised and misunderstood of problems.
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Artist (unnamed)
As an artist, I'm working on a community dance project. It will involve 500 dancers and the statistics suggest that we are only 10% human cells and 90% bacteria. That means that the average human has around 100 trillion microbes in and on their body. So with 500 dancers taking part, there will be 100 trillion times 500, which I think is is 50,000 trillion. Doing the sums on a calculator and I do hope I've done my sums correctly. I came up with 5e16, which is very enigmatic. As such, I have used 5e16 microbes on the move as the title.
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Ruth Alexander
Thank you to Nick, Kevin, Nicola, kp, Chris, Mike, Alastair and Bill. Please do email us if there are any statistics that have caught your eye or which you'd like us to factor Fact check. Our address is more or lessbc.co.uk and our website where you can find our free podcast is BBC.commoreorless
- [09:20]
BBC Announcer
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