The Mathematics of love

9 Feb

Steven Levingston reviews Hannah Fry: The Mathematics of Love

Steven Levingston is nonfiction editor of Book World and author of
“Little Demon in the City of Light: A True Story of Murder and
Mesmerism in Belle Époque Paris.”

The Mathematics of love
Patterns, Proofs, and the Search for the Ultimate Equation
By Hannah Fry
TED/Simon & Schuster.
113 pp. $16.99

Looking for a lover? Put down that comb, because it doesn’t matter
how hot you are. “Actually,” Hannah Fry explains in “The Mathematics
of Love,” “having some people think you are ugly can work in your
favor.” For online dating, you can even stop fretting over your
profile photo. Doing what most people do–hiding what makes you
look unattractive–is exactly what you shouldn’t do. “When
choosing a profile picture, you should play up to whatever makes you
different–including the things that some people might not like,”
Fry counsels. “So be proud of that bald patch, show off that
ill-advised tattoo, and get that belly out.”

By her own admission, Fry has had a lamentable love life: “a mixed
bag of successes mingled with a healthy series of disasters.” So why
should we listen to anything she says about matters of the heart?
Because, she asserts, she’s got mathematics on her side. Fry is a
30-something Brit, a mathematician and a complexity theorist who
studies the connections between mathematics and human interaction at
University College London. You can find her online giving TED talks
in which she presents mathematical analysis of her favorite
subjects: love and life’s complexity.
‘The Mathematics of Love: Patterns, Proofs, and the Search for the
Ultimate Equation’ by Hannah Fry. (TED Books/ )

And now, just in time for Valentine’s Day, she has expanded one
talk, “The Mathematics of Love,” into a smart, snappy guide to
romance that dips into mathematical models–the golden ratio,
regression analysis, the Gale-Shapley algorithm, discrete choice
theory–to illustrate successful strategies for leveraging your
looks, playing the online dating game, outdoing your friends in
party pickups and deciding whether to have a fling. On-screen and on
the page, Fry has a wry, chatty voice that illuminates age-old
questions in brainy yet simple language. She summarizes tricky
formulas but gladly admits that, when things get too gnarly for the
general reader, she will provide only an abbreviated explanation of,
say, optimal stopping theory, as this footnote reveals: “I’d like to
explain it properly, but it really does get quite complicated. And
let’s face it, we’ve all got lives to be getting on with.”

She dissects the patterns in the chaos of human relationships to
create tips for sorting through the mysteries of love, attraction
and beauty. She contends that long-held assumptions about beauty are
based on some faulty math and science, which is good news for those
who may not be gorgeous enough for the runway–that is, the
majority of us. She takes issue with a long-established belief that
human beauty is revealed in a mathematical concept called the
“golden ratio,” a number about equal to 1.61803399, which relates to
the optimal design characteristics of the face: “The perfect face
should have a mouth that is 1.618 … times larger than the base
of the nose, eyebrows that are 1.618 … times wider than the
eyes, and so on.” What’s troubling about the golden ratio as a
yardstick for beauty is the trickiness of the measurements required
to establish such a hard-and-fast rule. “How do you decide where the
‘start’ of your ear is,” she writes, “or the point at which your
nose definitively ‘ends’? And how do you do this to a degree of
accuracy of five or more decimal places in your golden ratio

Attraction, Fry gleefully reports, often sidesteps tidy mathematical
equations because of the role of personal preferences. But knowing
this, we can exploit mathematical formulas for luring the opposite
sex or the same sex, as the case may be. “People who are
unbelievably good looking,” she writes, “will always do well, of
course.” But in the online dating world, you don’t necessarily have
to be good-looking to be popular. Standing out–even for
unattractive physical characteristics–can be just as important.
Fry uses an analysis from the dating site OkCupid, co-founded by
mathematician Christian Rudder, that draws on a technique known as
regression analysis. OkCupid looked at the number of messages people
received based on how others measured their attractiveness. Here’s
the whopper: “Having people think you have a face like a dog’s
dinner means you get more messages,” Fry says. People who were rated
less attractive got more messages than people who were considered
quite attractive but not amazingly beautiful. It seems
counterintuitive, but, as Fry explains, “maybe what’s going on here
is that the users sending the messages are also thinking about their
own chances.”

If anyone still meets in the real world, Fry has the Gale-Shapley
algorithm to help explain how partners find success in matching up.
The algorithm suggests that people who make advances are much better
at getting a desired partner than those who sit back and wait for
someone to come to them. “If you put yourself out there, start at
the top of the list [of your desired partners], and work your way
down, you’ll always end up with the best possible person who’ll have
you,” Fry writes. “If you can handle the cringe-inducing rejection,
ultimately, taking the initiative will see you rewarded…. The
math says so.”

You can help your cause by understanding that people make decisions
based on options available to them, which in mathematical terms is
known as discrete choice theory. The equations indicate that people
follow fairly simple rules in making their decisions–and for
ambitious suitors, it’s good to know that people’s choices can be
easily manipulated. Fry draws on Dan Ariely’s work in behavioral
economics to show the power, both in the consumer world and in
dating, of a marketing ploy called the decoy effect. In marketing,
the effect tricks us into buying a large popcorn at the movie
theater after considering the varying prices of the small ($5)
medium ($8) and large ($8.50). The medium, at just 50 cents less
than the large, serves as a decoy to get us to spend extra for the

In dating, the decoy effect can be used to callous advantage while
party-hopping by bringing along a buddy who is just slightly less
attractive than you, so that you, like the minimally more expensive
large popcorn, seem like the better option to potential shoppers.

Now suppose you’ve learned your math well and have a steady partner.
But you still live in the real world among many temptations,
including the lure of a fling. Beginning with a look at what’s known
as the payoff matrix–the analysis of the pros and cons of a
decision–Fry concludes that, though in some circumstances one
party in the relationship may enjoy a greater payoff from an affair,
the long-term effects on trust and cooperation are detrimental.
“There’s little incentive to go for the short-term gain in cheating
given how much you stand to lose in the long run,” she writes.

And so, Fry concludes, simple mathematical rules can be useful in
life and love. “That’s why all mathematicians make famously
excellent lovers (and dancers),” she quips. “Who knew math could
give you such a lovely and moral way to live?”
Steven Levingston is the nonfiction editor of The Washington Post.
He is author of “Little Demon in the City of Light: A True Story of
Murder and Mesmerism in Belle Époque Paris” (Doubleday, 2014) and
“The Kennedy Baby: The Loss that Transformed JFK” (Washington Post
eBook, 2013).


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