Hannah Fry: The mathematics of love

Recorded atApril 04, 2014
EventTEDxBinghamtonUniversity
Duration (min:sec)16:52
Video TypeTEDx Talk
Words per minute192.7 fast
Readability (FK)46.92 difficult
SpeakerHannah Fry
CountryUnited Kingdom
Occupationmathematician, Q13590141, orator, author, Q901, lecturer
DescriptionBritish mathematician and TV presenter (1984-)

Official TED page for this talk

Synopsis

Finding the right mate is no cakewalk -- but is it even mathematically likely? In a charming talk, mathematician Hannah Fry shows patterns in how we look for love, and gives her top three tips (verified by math!) for finding that special someone.

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100:03 Today I want to talk to you about the mathematics of love.
200:08 Now, I think that we can all agree
300:09 that mathematicians are famously excellent at finding love.
400:13 (Laughter)
500:14 But it's not just because of our dashing personalities,
600:17 superior conversational skills and excellent pencil cases.
700:23 It's also because we've actually done an awful lot of work into the maths
800:26 of how to find the perfect partner.
900:29 Now, in my favorite paper on the subject, which is entitled,
1000:33 "Why I Don't Have a Girlfriend" --
1100:34 (Laughter)
1200:36 Peter Backus tries to rate his chances of finding love.
1300:40 Now, Peter's not a very greedy man.
1400:42 Of all of the available women in the UK,
1500:44 all Peter's looking for is somebody who lives near him,
1600:48 somebody in the right age range,
1700:49 somebody with a university degree,
1800:52 somebody he's likely to get on well with,
1900:54 somebody who's likely to be attractive,
2000:56 somebody who's likely to find him attractive.
2100:59 (Laughter)
2201:02 And comes up with an estimate of 26 women in the whole of the UK.
2301:07 (Laughter)
2401:08 It's not looking very good, is it Peter?
2501:10 Now, just to put that into perspective,
2601:12 that's about 400 times fewer than the best estimates
2701:15 of how many intelligent extraterrestrial life forms there are.
2801:19 And it also gives Peter a 1 in 285,000 chance
2901:24 of bumping into any one of these special ladies
3001:26 on a given night out.
3101:28 I'd like to think that's why mathematicians
3201:30 don't really bother going on nights out anymore.
3301:34 The thing is that I personally don't subscribe
3401:36 to such a pessimistic view.
3501:38 Because I know, just as well as all of you do,
3601:40 that love doesn't really work like that.
3701:43 Human emotion isn't neatly ordered and rational and easily predictable.
3801:48 But I also know that that doesn't mean
3901:50 that mathematics hasn't got something that it can offer us,
4001:53 because, love, as with most of life, is full of patterns
4101:57 and mathematics is, ultimately, all about the study of patterns.
4202:02 Patterns from predicting the weather to the fluctuations in the stock market,
4302:06 to the movement of the planets or the growth of cities.
4402:09 And if we're being honest, none of those things
4502:11 are exactly neatly ordered and easily predictable, either.
4602:15 Because I believe that mathematics is so powerful that it has the potential
4702:21 to offer us a new way of looking at almost anything.
4802:24 Even something as mysterious as love.
4902:27 And so, to try to persuade you
5002:29 of how totally amazing, excellent and relevant mathematics is,
5102:34 I want to give you my top three mathematically verifiable tips for love.
5202:41 (Laughter)
5302:43 OK, so Top Tip #1:
5402:45 How to win at online dating.
5502:49 So my favorite online dating website is OkCupid,
5602:52 not least because it was started by a group of mathematicians.
5702:56 Now, because they're mathematicians,
5802:58 they have been collecting data
5902:59 on everybody who uses their site for almost a decade.
6003:03 And they've been trying to search for patterns
6103:05 in the way that we talk about ourselves
6203:07 and the way that we interact with each other
6303:09 on an online dating website.
6403:10 And they've come up with some seriously interesting findings.
6503:13 But my particular favorite
6603:15 is that it turns out that on an online dating website,
6703:18 how attractive you are does not dictate how popular you are,
6803:24 and actually, having people think that you're ugly
6903:28 can work to your advantage.
7003:30 (Laughter)
7103:31 Let me show you how this works.
7203:33 In a thankfully voluntary section of OkCupid,
7303:37 you are allowed to rate how attractive you think people are
7403:40 on a scale between one and five.
7503:42 Now, if we compare this score, the average score,
7603:45 to how many messages a selection of people receive,
7703:49 you can begin to get a sense
7803:50 of how attractiveness links to popularity on an online dating website.
7903:55 This is the graph the OkCupid guys have come up with.
8003:58 And the important thing to notice is that it's not totally true
8104:01 that the more attractive you are, the more messages you get.
8204:04 But the question arises then of what is it about people up here
8304:08 who are so much more popular than people down here,
8404:12 even though they have the same score of attractiveness?
8504:15 And the reason why is that it's not just straightforward looks that are important.
8604:19 So let me try to illustrate their findings with an example.
8704:22 So if you take someone like Portia de Rossi, for example,
8804:26 everybody agrees that Portia de Rossi is a very beautiful woman.
8904:30 Nobody thinks that she's ugly, but she's not a supermodel, either.
9004:34 If you compare Portia de Rossi to someone like Sarah Jessica Parker,
9104:39 now, a lot of people, myself included, I should say,
9204:43 think that Sarah Jessica Parker is seriously fabulous
9304:47 and possibly one of the most beautiful creatures
9404:50 to have ever have walked on the face of the Earth.
9504:52 But some other people, i.e., most of the Internet ...
9604:57 (Laughter)
9704:59 seem to think that she looks a bit like a horse.
9805:01 (Laughter)
9905:04 Now, I think that if you ask people how attractive they thought
10005:08 Jessica Parker or Portia de Rossi were,
10105:10 and you ask them to give them a score between one and five
10205:13 I reckon that they'd average out to have roughly the same score.
10305:16 But the way that people would vote would be very different.
10405:19 So Portia's scores would all be clustered around the four
10505:22 because everybody agrees that she's very beautiful,
10605:24 whereas Sarah Jessica Parker completely divides opinion.
10705:27 There'd be a huge spread in her scores.
10805:29 And actually it's this spread that counts.
10905:31 It's this spread that makes you more popular
11005:33 on an online Internet dating website.
11105:36 So what that means then
11205:37 is that if some people think that you're attractive,
11305:39 you're actually better off
11405:41 having some other people think that you're a massive minger.
11505:46 That's much better than everybody just thinking
11605:49 that you're the cute girl next door.
11705:51 Now, I think this begins to make a bit more sense
11805:53 when you think in terms of the people who are sending these messages.
11905:56 So let's say that you think somebody's attractive,
12005:59 but you suspect that other people won't necessarily be that interested.
12106:03 That means there's less competition for you
12206:05 and it's an extra incentive for you to get in touch.
12306:08 Whereas compare that to if you think somebody is attractive
12406:11 but you suspect that everybody is going to think they're attractive.
12506:14 Well, why would you bother humiliating yourself, let's be honest?
12606:18 But here's where the really interesting part comes.
12706:20 Because when people choose the pictures that they use on an online dating website,
12806:24 they often try to minimize the things
12906:26 that they think some people will find unattractive.
13006:30 The classic example is people who are, perhaps, a little bit overweight
13106:34 deliberately choosing a very cropped photo,
13206:36 (Laughter)
13306:38 or bald men, for example,
13406:39 deliberately choosing pictures where they're wearing hats.
13506:42 But actually this is the opposite of what you should do
13606:45 if you want to be successful.
13706:46 You should really, instead,
13806:48 play up to whatever it is that makes you different,
13906:51 even if you think that some people will find it unattractive.
14006:55 Because the people who fancy you are just going to fancy you anyway,
14106:58 and the unimportant losers who don't, well, they only play up to your advantage.
14207:03 OK, Top Tip #2: How to pick the perfect partner.
14307:05 So let's imagine then that you're a roaring success
14407:08 on the dating scene.
14507:10 But the question arises of how do you then convert that success
14607:14 into longer-term happiness,
14707:17 and in particular, how do you decide when is the right time to settle down?
14807:22 Now generally, it's not advisable to just cash in
14907:25 and marry the first person who comes along and shows you any interest at all.
15007:29 But, equally, you don't really want to leave it too long
15107:32 if you want to maximize your chance of long-term happiness.
15207:35 As my favorite author, Jane Austen, puts it,
15307:38 "An unmarried woman of seven and twenty
15407:41 can never hope to feel or inspire affection again."
15507:44 (Laughter)
15607:47 Thanks a lot, Jane.
15707:48 What do you know about love?
15807:49 (Laughter)
15907:50 So the question is then,
16007:52 how do you know when is the right time to settle down,
16107:55 given all the people that you can date in your lifetime?
16207:58 Thankfully, there's a rather delicious bit of mathematics that we can use
16308:01 to help us out here, called optimal stopping theory.
16408:04 So let's imagine, then,
16508:06 that you start dating when you're 15
16608:08 and ideally, you'd like to be married by the time that you're 35.
16708:12 And there's a number of people
16808:14 that you could potentially date across your lifetime,
16908:16 and they'll be at varying levels of goodness.
17008:18 Now the rules are that once you cash in and get married,
17108:21 you can't look ahead to see what you could have had,
17208:23 and equally, you can't go back and change your mind.
17308:26 In my experience at least,
17408:28 I find that typically people don't much like being recalled
17508:30 years after being passed up for somebody else, or that's just me.
17608:36 So the math says then that what you should do
17708:39 in the first 37 percent of your dating window,
17808:42 you should just reject everybody as serious marriage potential.
17908:46 (Laughter)
18008:48 And then, you should pick the next person that comes along
18108:52 that is better than everybody that you've seen before.
18208:55 So here's the example.
18308:56 Now if you do this, it can be mathematically proven, in fact,
18408:59 that this is the best possible way
18509:01 of maximizing your chances of finding the perfect partner.
18609:06 Now unfortunately, I have to tell you that this method does come with some risks.
18709:11 For instance, imagine if your perfect partner appeared
18809:16 during your first 37 percent.
18909:19 Now, unfortunately, you'd have to reject them.
19009:21 (Laughter)
19109:25 Now, if you're following the maths,
19209:27 I'm afraid no one else comes along
19309:28 that's better than anyone you've seen before,
19409:31 so you have to go on rejecting everyone and die alone.
19509:35 (Laughter)
19609:37 Probably surrounded by cats ...
19709:39 (Laughter)
19809:40 nibbling at your remains.
19909:42 OK, another risk is, let's imagine, instead,
20009:46 that the first people that you dated in your first 37 percent
20109:49 are just incredibly dull, boring, terrible people.
20209:53 That's OK, because you're in your rejection phase,
20309:56 so that's fine, you can reject them.
20409:58 But then imagine the next person to come along
20510:01 is just marginally less boring, dull and terrible ...
20610:04 (Laughter)
20710:05 than everybody that you've seen before.
20810:07 Now, if you are following the maths, I'm afraid you have to marry them ...
20910:11 (Laughter)
21010:12 and end up in a relationship which is, frankly, suboptimal.
21110:15 Sorry about that.
21210:16 But I do think that there's an opportunity here for Hallmark to cash in on
21310:20 and really cater for this market.
21410:21 A Valentine's Day card like this.
21510:23 (Laughter)
21610:24 "My darling husband, you are marginally less terrible
21710:27 than the first 37 percent of people I dated."
21810:29 (Laughter)
21910:31 It's actually more romantic than I normally manage.
22010:34 (Laughter)
22110:36 OK, so this method doesn't give you a 100 percent success rate,
22210:40 but there's no other possible strategy that can do any better.
22310:44 And actually, in the wild, there are certain types of fish
22410:47 which follow and employ this exact strategy.
22510:50 So they reject every possible suitor that turns up
22610:53 in the first 37 percent of the mating season,
22710:56 and then they pick the next fish that comes along after that window
22810:59 that's, I don't know, bigger and burlier
22911:02 than all of the fish that they've seen before.
23011:04 I also think that subconsciously, humans, we do sort of do this anyway.
23111:09 We give ourselves a little bit of time to play the field,
23211:12 get a feel for the marketplace or whatever when we're young.
23311:16 And then we only start looking seriously at potential marriage candidates
23411:20 once we hit our mid-to-late 20s.
23511:22 I think this is conclusive proof, if ever it were needed,
23611:26 that everybody's brains are prewired to be just a little bit mathematical.
23711:30 OK, so that was Top Tip #2.
23811:32 Now, Top Tip #3: How to avoid divorce.
23911:36 OK, so let's imagine then that you picked your perfect partner
24011:39 and you're settling into a lifelong relationship with them.
24111:43 Now, I like to think that everybody would ideally like to avoid divorce,
24211:47 apart from, I don't know, Piers Morgan's wife, maybe?
24311:51 (Laughter)
24411:53 But it's a sad fact of modern life
24511:55 that one in two marriages in the States ends in divorce,
24611:58 with the rest of the world not being far behind.
24712:02 Now, you can be forgiven, perhaps
24812:04 for thinking that the arguments that precede a marital breakup
24912:08 are not an ideal candidate for mathematical investigation.
25012:12 For one thing, it's very hard to know
25112:14 what you should be measuring or what you should be quantifying.
25212:17 But this didn't stop a psychologist, John Gottman, who did exactly that.
25312:23 Gottman observed hundreds of couples having a conversation
25412:28 and recorded, well, everything you can think of.
25512:31 So he recorded what was said in the conversation,
25612:33 he recorded their skin conductivity,
25712:35 he recorded their facial expressions,
25812:37 their heart rates, their blood pressure,
25912:39 basically everything apart from whether or not the wife was actually always right,
26012:46 which incidentally she totally is.
26112:49 But what Gottman and his team found
26212:52 was that one of the most important predictors
26312:55 for whether or not a couple is going to get divorced
26412:57 was how positive or negative each partner was being in the conversation.
26513:02 Now, couples that were very low-risk
26613:04 scored a lot more positive points on Gottman's scale than negative.
26713:08 Whereas bad relationships,
26813:11 by which I mean, probably going to get divorced,
26913:14 they found themselves getting into a spiral of negativity.
27013:18 Now just by using these very simple ideas,
27113:20 Gottman and his group were able to predict
27213:23 whether a given couple was going to get divorced
27313:26 with a 90 percent accuracy.
27413:29 But it wasn't until he teamed up with a mathematician, James Murray,
27513:32 that they really started to understand
27613:34 what causes these negativity spirals and how they occur.
27713:38 And the results that they found,
27813:40 I think, are just incredibly impressively simple and interesting.
27913:45 So these equations predict how the wife or husband is going to respond
28013:49 in their next turn of the conversation,
28113:51 how positive or negative they're going to be.
28213:53 And these equations depend on
28313:55 the mood of the person when they're on their own,
28413:57 the mood of the person when they're with their partner,
28514:00 but most importantly, they depend on
28614:01 how much the husband and wife influence one another.
28714:05 Now, I think it's important to point out at this stage,
28814:07 that these exact equations have also been shown
28914:11 to be perfectly able at describing
29014:13 what happens between two countries in an arms race.
29114:18 (Laughter)
29214:21 So that an arguing couple spiraling into negativity
29314:24 and teetering on the brink of divorce
29414:26 is actually mathematically equivalent to the beginning of a nuclear war.
29514:31 (Laughter)
29614:34 But the really important term in this equation
29714:36 is the influence that people have on one another,
29814:38 and in particular, something called "the negativity threshold."
29914:42 Now, the negativity threshold,
30014:43 you can think of as how annoying the husband can be
30114:48 before the wife starts to get really pissed off, and vice versa.
30214:52 Now, I always thought that good marriages were about compromise and understanding
30314:57 and allowing the person to have the space to be themselves.
30415:00 So I would have thought that perhaps the most successful relationships
30515:03 were ones where there was a really high negativity threshold.
30615:06 Where couples let things go
30715:08 and only brought things up if they really were a big deal.
30815:11 But actually, the mathematics and subsequent findings by the team
30915:15 have shown the exact opposite is true.
31015:18 The best couples, or the most successful couples,
31115:21 are the ones with a really low negativity threshold.
31215:24 These are the couples that don't let anything go unnoticed
31315:28 and allow each other some room to complain.
31415:31 These are the couples that are continually trying to repair their own relationship,
31515:36 that have a much more positive outlook on their marriage.
31615:39 Couples that don't let things go
31715:41 and couples that don't let trivial things end up being a really big deal.
31815:47 Now of course, it takes a bit more than just a low negativity threshold
31915:52 and not compromising to have a successful relationship.
32015:57 But I think that it's quite interesting
32115:59 to know that there is really mathematical evidence
32216:02 to say that you should never let the sun go down on your anger.
32316:05 So those are my top three tips
32416:07 of how maths can help you with love and relationships.
32516:10 But I hope, that aside from their use as tips,
32616:12 they also give you a little bit of insight into the power of mathematics.
32716:16 Because for me, equations and symbols aren't just a thing.
32816:21 They're a voice that speaks out about the incredible richness of nature
32916:26 and the startling simplicity
33016:27 in the patterns that twist and turn and warp and evolve all around us,
33116:32 from how the world works to how we behave.
33216:35 So I hope that perhaps, for just a couple of you,
33316:37 a little bit of insight into the mathematics of love
33416:40 can persuade you to have a little bit more love for mathematics.
33516:43 Thank you.
33616:44 (Applause)
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