Today I want to talk to you about the mathematics of love.
I think we can all agree that mathematicians
are famously excellent at finding love.
But it's not just because of our dashing personalities
our superior conversational skills, our our excellent pencil cases,
It's also because we've done a lot of work into the maths
of how to find the perfect partner.
In my favorite paper on the subject, which is entitled,
"Why I Don't Have a Girlfriend", Peter Backus tries to rate
his chances at finding love.
Now, peter is not a very greedy man.
Of all of the available women in the UK,
all that 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 attractive,
somebody who is likely to find him attractive
(Laughter),
and comes up with an estimate of 26 women
in the whole of the UK.
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 extra-terrestrial 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 night out.
I'd like to think that's why mathematicians don't really bother
going on nights out anymore.
The thing is is that I personally
don't subscribe to such a pessimistic view.
I know, just as well as you do,
that love doesn't really work like that
human emotion isn't neatly ordered,
rational, or easily predictable.
But I also know that that doesn't mean that mathematics
doesn't have something 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 of the stock market,
to the movement of the planets,
or the growth of cities.
If we're being honest, none of those things are neatly ordered
Or easily predictable, either.
Because I believe that mathematics
is so powerful that is 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, excellent and relevant mathematics is,
I want to give you my top three mathematically verifiable tips for love.
Okay, so top tip #1:
How to win at online dating.
So my favorite online dating website
is OkayCupid,
not least because it was
started by a group of mathematicians.
Now because they're mathematicians,
they have been collecting data on everyone
whose been using 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 online dating websites.
And they've come up with 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.
Let me show you how this works.
Okay, in a thankfully voluntary section,
you are allowed to rate how attractive people are
between 1 and 5.
And if we compare this score, this 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 online dating.
So this is a graph that the online
OkayCupid 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?
same score of attractiveness
and the reason why is that
it's not just straight forward looks
that are important
so, let me try to illustrate their findings
with an example
if you take someone like porcia di rossi
everybody agrees that porcia di rossi
is a very beautiful woman
nobody thinks that she's ugly
but she's not a supermodel
if you compare porcia di rossi
to someone like sarah jessica parker
now, a lot of people
myself included
think that sarah jessica parker
is seriously fabulous
and possibly one of
the most beautiful creatures to have evr
walked the face of the earth
but, some other people
e.i., most of the internet
seem to think that she looks a bit like a horse
(laughter)
now, i think that if you ask people
how attractive sarah jessica parker or porcia di rossi are
and you ask them to give them a score between one and five
i reckon that they would average out to the same score
but the way that people would vote
would be dry different
so porcia's scores would all be clustered around
the four because everybody agrees that she's
very beautiful
whereas sarah jessica parker divides opinion
there a huge spread in her scores
and actually it's this spread that counts
it's this spread that makes you more popular
on online internet dating websites
so what this 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 thinking that you're the cute girl next door
i think that this makes 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 that there is less competition for you
and that there'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
here's where the really interesting part comes
people choose the pictures that they use on an online, dating website
they often try to minimize the things
that they think people will find unattractive
the classic example is that
people who are a little but overweight
deliberately choosing a very cropped phto
or bald men for example
deliberatly choosing pictures
where they're wearing hats
but this is the opposite of
what you should do if
want to be succesful
you should really instead
play up to whatever it is that makes you different
even if you think that
some people will find you 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 out to you r advantage
Okay, 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 the first person
who comes along and shows you any interest
at all
but, equally, you don't want to leave it
too long if you want to maximize your chances of long term happiness
as my favorite author, jane austen put it,
"an unmarried woman of seven and twenty
can never hope to feel or
inspire affection again."
laughter
thanks, jane
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 is a rather delicious bit
of mathematics that we can use to
help us out here
so lets imagine then,
that you start dating when you're 15
and ideally, you'd like to be
married by the time you're 35
the number of people that you
could potentially date across your lifetime
and they'll be at kind of varying levels
of goodness
now the rules are that when you cash in
and get married
you can't look ahead and 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 people don't typically
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 reject everybody as serious marriage potential
and then, you should pick the next person who comes along
who is better than everyone 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 your 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 Uunfortunately, you'd have to reject them
now, if you're following the maths
im afraid that no one else comes along
better than anyone you've seen before
so you have to go on rejecting everyone
and die along
laughter
probably surrounded by cats
nibbling at your remains
okay, another risk
is, let's imagine instead
that the first people that you dated
in your first 37 percent are just incredibly
dull, terrible people
now, that's okay, cause you're in your
rejection phase, so you can reject them
but, then imagine that
the next person to cmd along
is just marginally less boring, dull and terrible
than everybody that you've seen before.
now, if you are following the maths
im afraid that you have to
marry them
and end up in a relationship
that 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 to this market
with a valentines day card like this
[my darling husband,
you are marginally less terrible
than the first 37 percent
of people i dated]
it's actually more romantic
than i normally manage
okay, 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 that follow
this exct strategy
so they reject every possible suitor that turns up in
in the first 37 percent of the mating season, then they
pick the next fish
who comes along after
that window who is, i don't know
bigger and burlier than all the fish that they've seen
i also think that subconsciously
humans, we sort of do this anyway
we give ourselves enough time to
play the field, get a feel for the market place
or whatever
when we're young
and then we only start looking seriously at
potential marriage candidates when we hit
our mid to late 20's
i think this is conclusive prrof
if ever it were needed
that everybody's brains are prewired to be
just a little bit mathematical
okay, so that was top tip #2
top tip #3 how to avoid divorse
okay so let's imagine then that yu
picked your perfect partner
and you're settling into a lifelong relationship with them
now, i like to think that everybody
would like to avoid divorce
from, piers morgan's wife, maybe?
but it's a sad fact in modern life
that one in two marriages end 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, it's very hard to know what you should
be measuring and what you should be
quantifying.
but this didn't stop a psychologist,
john gotman,
who did exactly THAT
he observed, hotman observed
hundreds of couples having a conversation
and recorded well, everything you could think of
so he recorded what was said in the conversation
he recorded skin conductivity
he recorded their facial expresisons
heart rates, their blood pressure
basically everything apart
from whether or not the wife was always right
, which incidentally she totally is
but what got man found
what got man and his team found
was that one of the most
important predictors for whether
or not a couple is going to get divorced
is how positive or negative
each partner was being in the conversation
now couples that were very low risk
scored a lot more positive on got man's scale
than negative.
whereas bad relationship
as in, those that are pribably
going to get divorced,
they found themselves getting into
a spiral of negativity
now just by using these very simple ideas
gotman 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 caused
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, they predict
how the wife or husband is going
to respond in the next turn of the conversation
how positive or negative they're going to be
and these equations, they depend on
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
that at this stage that these exact
equations have also been shown t
to be perfectly
able to describe what happens between two
countries in an arms race
laughter
so that an arguing couple
spiraling into negativity
teetering on the brink of divoirce
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 threshhold
now the negativity threshhold
you can think of as
how annoying the husband can
be before the wife starts to get really pissed of
and vice versa
now i always thought that good marriages
are 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
are the ones where there is
a really high negativity threshhold
where couples let things go
and only brought things up if there
really were a big deal
but actually, the mathematics
and subsequent findings by the team
have shown that the exact opposite is true
the best couples of the most successful couples
are the ones are the ones with a
really low negativity threshold
these are the couples that
don't let anything go unnoticed
they 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 more than just a low negativity
threshold and not compromising
to have a succesful relationship
but i think that it's quite interesting
to know that there is really
mathematical evidence to support that
you should never let the sun
go down on your anger
so those are my top three tips for how
maths can help you with
love and relaitonships
but i hope that aside form
these aside form these tips
they also give you a little bit of
insight into the power of mathematics
because for me,
equationsand symbols
aren't just a thing
they are 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
around us
from how the world wokrs
to how we behave
so i hope that perhaps
for just a couple of you
a little bit of insight into
mathematics of love
can persuade you
to have a little bit more love
for mathematics
thank you
applause