All you need is maths? The man using equations to find love
They say love is a numbers game. Bobby Seagull – the mathematician who rose to fame as a finalist on University Challenge in 2017 – took them literally.
A few years ago, he sat down to try to work out why he had been so unlucky in life. “I was 32 or 33, I was single, I loved maths and science – I thought: ‘Can I use maths and science to help me?’ It was a genuine, earnest attempt.”
Inspired by Peter Backus – a Manchester University economics lecturer who in 2010 wrote a paper titled Why I Don’t Have a Girlfriend – Seagull used the Drake equation, developed to estimate how many intelligent alien civilisations there might be in the galaxy, to determine his number of potential partners. “You start by assuming there’s infinitely many, then you keep on making the pool smaller and smaller.”
From the total female populations of London and Cambridge – the cities between which he split his time – Seagull selected those roughly his age and up to 10 years younger. Then he reduced that group to the proportion that were likely to be university educated, to reflect the reality of his networks, as a school maths teacher and doctorate student.
Then came a harder parameter: what fraction Seagull might find attractive. After going through his Facebook friends list, he found 1,200 women who met his criteria for age, location and education – and of one in every 20, he says he thought that he “could imagine us, in another life”.
That left Seagull with 29,369 potential girlfriends: as he puts it, a decentsized crowd at the old West Ham ground at Upton Park. But that did not account for two important factors: his next girlfriend would have to be single – and she would have to find him attractive, too.
Seagull found himself with a final total of 73. Whether that figure floods you with optimism or despair may mark you out as a romantic or a realist. On one hand, it’s nowhere close to filling up a football stadium. On the other, it is significantly greater than one. As in, the One.
Numbers have long factored into the dating game, even for those who have a ropey grasp on them. We might wonder, of a couple’s particularly serendipitous origin story: “What are the chances?” Or we might console someone who is unhappily single that “it only takes one”.
Online dating has strengthened mathematics’ role in the search for love, not only in serving up seemingly infinite potential partners, but in using algorithms to sift through them. As it is increasingly accepted that there is no perfect one for each of us, the numbers are on our side – but that doesn’t mean the search is easy.
“I think there are many ‘ones’,” says Seagull. “There are 107 billion people who have ever existed – if you really think there is one person who is truly your ‘one’, they’ve probably died.”
Now 35 and still single, Seagull has continued his investigation into “making the maths of love work for you” in his book, The Life-Changing Magic of Numbers, as well as on dates. When he had reached that 73 figure, he says, he showed his working to his mum as a somewhat tongue-in-cheek rebuttal to her persistent inquiries as to why he didn’t have a girlfriend.
“The reality is, that’s on paper – it doesn’t tell you whether you’re compatible in person. On paper, I’m probably a perfect match with my dad, if he was a woman, and not related to me.
“And that’s 73 people that I think would be a perfect fit for me – I may not be a perfect fit for them.”
Perhaps understandably, on being confronted by a pool of potential partners who could fit comfortably on one double-decker bus, Seagull says he has learned the need to relax his criteria. After all, he says, the mathematician Hannah Fry found that the most successful couples have a “low negativity threshold”, meaning they argue often but easily move on. “Then you’ve got to start thinking: what’s the most efficient way of dating people so that you can quickly establish their potential?”
Seagull supports a “little bit of stress-testing” even at the dating stage; his suggestion is to bring up Brexit, less to weed out leave or remain voters than to test a potential partner’s capacity for disagreement. (Excluding leave voters would further reduce his pool from 73 to about 40, he says, sounding dismayed.)
Like the Drake equation, online dating can present you only with a pool of suitable partners you could potentially meet. Attraction must be assessed in person, “and there is no formula for that”, says Seagull. Or at least not yet, he adds; he is confident that machinelearning technology will eventually be able “to read your mood, your mind … and detect bits of our personality” to predict the presence of that elusive spark.
In decades to come, it may even be possible to simulate dates the same way that it is football matches now, modelling every variable – although, Seagull says, probably not soon enough to be of any use to him.
For now, the most efficient approach to dating is to meet as many potential partners as possible – and apps connect us with a seemingly infinite number. There can often be an element of the paradox of choice: sure, this match seems good, but what if an even better one is a swipe away?
This is where optimal-stopping theory can come into play, identifying the point in a process at which to stop for best results – and here the magic number, says Seagull, is 37%. Say he wanted to be in a relationship by the age of 40, and was prepared to commit to going on two dates a week, for 50 weeks of the year, for five years: 500 dates total. Optimal-stopping theory would have Seagull go on 185 dates – taking him the best part of two years – then, armed with the insights he gained along the way, pursue the woman he liked best from the 186th on.
“You don’t know at what stage in these 500 dates you will meet your most suited person, and you’re probably going to miss them – but mathematically, this is how you can settle better.
“This is where you really need to trust the maths – you might think that the first person you meet is amazing, but you’ve got to get through the first 185. If we simulated our lives a million times, the person that you would date best would still be after 185.”
Keeping track of that number would inevitably necessitate a spreadsheet, or at least note-taking, which even Seagull sees as a step too far: “I haven’t got that cynical yet.”
The key to bear in mind, he says, is that “once you’ve got your potential pool, you need to maximise your chances by meeting as many of them as quickly as possible” – before they get coupled up, leave the country or otherwise remove themselves.
There is evidence to support coming to a conclusion about potential partners quickly – even if by gut feeling alone. In 2012, the US mathematician Chris McKinlay successfully hacked dating site Ok Cupid to identify his best matches, then – through trial and error – perfected his own formula for dates: no alcohol; a definite endpoint – no trailing off; and no concerts, films or anything similarly “inefficient”, as he told Wired’s Kevin Poulsen.
Once, he took different dates to the same beach, on the same day. It worked for McKinlay (and his fiancee found the story amusing), but Seagull says he has had the opposite approach, being “very strict about the swipe process” and less disciplined about the actual dates.
He intends to take a leaf from McKinlay’s workbook and relax his criteria, have more and shorter dates – and to avoid alcohol. “You can’t have things that cloud your data set.” But Seagull shies from McKinlay’s tactic of sending the same, boilerplate message to matches he wanted to meet (“You seem really cool. Want to meet?”).
“The thing about maths is, it can make you feel a bit cynical sometimes when you’re on dates, going through their personality traits. I think it should be a guidance. Maths can’t take into account every single possible factor.” Such as, for example, human emotions – although those don’t always make dating easier, either, says Seagull.
I am surprised to learn that he has only been on seven or eight dates since doing Drake’s equation a few years ago. Maybe his mum was right when, on seeing his formula, she told him he was being ridiculous, and “to go out and meet people”.
“I’m terrible,” he admits. “I leave a long gap between dates. After a date, if you didn’t have a good time, you feel despondent. I had another date, where I liked her and she didn’t like me. As a human, you get upset. That’s why scientists trust the maths: keep going.”
Bobby Seagull will present his Mathematician’s Guide to Dating at New Scientist Live, ExCel London, on 11 October