How your brain decides what is beautiful | Anjan Chatterjee

It's 1878.

Sir Francis Galton gives a remarkable talk.

He's speaking to the anthropologic institute of Great Britain and Ireland.

Known for his pioneering work in human intelligence,

Galton is a brilliant polymath.

He's an explorer,

an anthropologist,

a sociologist,

a psychologist

and a statistician.

He's also a eugenist.

In this talk,

he presents a new technique by which he can combine photographs

and produce composite portraits.

This technique could be used to characterize different types of people.

Galton thinks that if he combines photographs of violent criminals,

he will discover the face of criminality.

But to his surprise,

the composite portrait that he produces

is beautiful.

Galton's surprising finding raises deep questions:

What is beauty?

Why do certain configurations of line and color and form excite us so?

For most of human history,

these questions have been approached using logic and speculation.

But in the last few decades,

scientists have addressed the question of beauty

using ideas from evolutionary psychology and tools of neuroscience.

We're beginning to glimpse the why and the how of beauty,

at least in terms of what it means for the human face and form.

And in the process,

we're stumbling upon some surprises.

When it comes to seeing beauty in each other,

while this decision is certainly subjective for the individual,

it's sculpted by factors that contribute to the survival of the group.

Many experiments have shown

that a few basic parameters contribute to what makes a face attractive.

These include averaging, symmetry and the effects of hormones.

Let's take each one of these in turn.

Galton's finding

that composite or average faces are typically more attractive

than each individual face that contributes to the average

has been replicated many times.

This laboratory finding fits with many people's intuitions.

Average faces represent the central tendencies of a group.

People with mixed features represent different populations,

and presumably harbor greater genetic diversity

and adaptability to the environment.

Many people find mixed-race individuals attractive

and inbred families less so.

The second factor that contributes to beauty is symmetry.

People generally find symmetric faces more attractive than asymmetric ones.

Developmental abnormalities are often associated with asymmetries.

And in plants, animals and humans,

asymmetries often arise from parasitic infections.

Symmetry, it turns out,

is also an indicator of health.

In the 1930s,

a man named Maksymilian Faktorowicz

recognized the importance of symmetry for beauty

when he designed the beauty micrometer.

With this device,

he could measure minor asymmetric flaws

which he could then make up for with products he sold from his company,

named brilliantly after himself, Max Factor,

which, as you know, is one of the world's most famous brands

for "make up."

The third factor that contributes to facial attractiveness

is the effect of hormones.

And here, I need to apologize for confining my comments

to heterosexual norms.

But estrogen and testosterone play important roles

in shaping features that we find attractive.

Estrogen produces features that signal fertility.

Men typically find women attractive

who have elements of both youth and maturity.

A face that's too baby-like might mean that the girl is not yet fertile,

so men find women attractive

who have large eyes, full lips and narrow chins

as indicators of youth,

and high cheekbones as an indicator of maturity.

Testosterone produces features that we regard as typically masculine.

These include heavier brows,

thinner cheeks

and bigger, squared-off jaws.

But here's a fascinating irony.

In many species,

if anything,

testosterone suppresses the immune system.

So the idea that testosterone-infused features are a fitness indicator

doesn't really make a whole lot of sense.

Here, the logic is turned on its head.

Instead of a fitness indicator,

scientists invoke a handicap principle.

The most commonly cited example of a handicap

is the peacock's tail.

This beautiful but cumbersome tail doesn't exactly help the peacock

avoid predators

and approach peahens.

Why should such an extravagant appendage evolve?

Even Charles Darwin,

in an 1860 letter to Asa Gray wrote

that the sight of the peacock's tail made him physically ill.

He couldn't explain it with his theory of natural selection,

and out of this frustration,

he developed the theory of sexual selection.

On this account,

the display of the peacock's tail is about sexual enticement,

and this enticement means it's more likely the peacock will mate

and have offspring.

Now, the modern twist on this display argument

is that the peacock is also advertising its health to the peahen.

Only especially fit organisms can afford to divert resources

to maintaining such an extravagant appendage.

Only especially fit men can afford the price that testosterone levies

on their immune system.

And by analogy, think of the fact

that only very rich men can afford to pay more than $10,000 for a watch

as a display of their financial fitness.

Now, many people hear these kinds of evolutionary claims

and think they mean that we somehow are unconsciously seeking mates

who are healthy.

And I think this idea is probably not right.

Teenagers and young adults are not exactly known for making decisions

that are predicated on health concerns.

But they don't have to be,

and let me explain why.

Imagine a population

in which people have three different kinds of preferences:

for green, for orange and for red.

From their point of view,

these preferences have nothing to do with health;

they just like what they like.

But if it were also the case that these preferences are associated

with the different likelihood of producing offspring --

let's say in a ratio of 3:2:1 --

then in the first generation,

there would be 3 greens to 2 oranges to 1 red,

and in each subsequent generation,

the proportion of greens increase,

so that in 10 generations,

98 percent of this population has a green preference.

Now, a scientist coming in and sampling this population

discovers that green preferences are universal.

So the point about this little abstract example

is that while preferences for specific physical features

can be arbitrary for the individual,

if those features are heritable

and they are associated with a reproductive advantage,

over time,

they become universal for the group.

So what happens in the brain when we see beautiful people?

Attractive faces activate parts of our visual cortex

in the back of the brain,

an area called the fusiform gyrus,

that is especially tuned to processing faces,

and an adjacent area called the lateral occipital complex,

that is especially attuned to processing objects.

In addition,

attractive faces activate parts of our reward and pleasure centers

in the front and deep in the brain,

and these include areas that have complicated names,

like the ventral striatum,

the orbitofrontal cortex

and the ventromedial prefrontal cortex.

Our visual brain that is tuned to processing faces

interacts with our pleasure centers

to underpin the experience of beauty.

Amazingly, while we all engage with beauty,

without our knowledge,

beauty also engages us.

Our brains respond to attractive faces

even when we're not thinking about beauty.

We conducted an experiment in which people saw a series of faces,

and in one condition,

they had to decide if a pair of faces were the same or a different person.

Even in this condition,

attractive faces drove neural activity robustly in their visual cortex,

despite the fact that they were thinking about a person's identity

and not their beauty.

Another group similarly found automatic responses to beauty

within our pleasure centers.

Taken together, these studies suggest

that our brain automatically responds to beauty

by linking vision and pleasure.

These beauty detectors, it seems,

ping every time we see beauty,

regardless of whatever else we might be thinking.

We also have a "beauty is good" stereotype embedded in the brain.

Within the orbitofrontal cortex,

there's overlapping neural activity

in response to beauty and to goodness,

and this happens even when people aren't explicitly thinking

about beauty or goodness.

Our brains seem to reflexively associate beauty and good.

And this reflexive association may be the biologic trigger

for the many social effects of beauty.

Attractive people receive all kinds of advantages in life.

They're regarded as more intelligent,

more trustworthy,

they're given higher pay and lesser punishments,

even when such judgments are not warranted.

These kinds of observations reveal beauty's ugly side.

In my lab, we recently found

that people with minor facial anomalies and disfigurements

are regarded as less good, less kind,

less intelligent, less competent and less hardworking.

Unfortunately, we also have a "disfigured is bad" stereotype.

This stereotype is probably exploited and magnified

by images in popular media,

in which facial disfigurement is often used as a shorthand

to depict someone of villainous character.

We need to understand these kinds of implicit biases

if we are to overcome them

and aim for a society in which we treat people fairly,

based on their behavior and not on the happenstance of their looks.

Let me leave you with one final thought.

Beauty is a work in progress.

The so-called universal attributes of beauty

were selected for during the almost two million years of the Pleistocene.

Life was nasty, brutish and a very long time ago.

The selection criteria for reproductive success from that time

doesn't really apply today.

For example,

death by parasite is not one of the top ways that people die,

at least not in the technologically developed world.

From antibiotics to surgery,

birth control to in vitro fertilization,

the filters for reproductive success are being relaxed.

And under these relaxed conditions,

preference and trait combinations are free to drift

and become more variable.

Even as we are profoundly affecting our environment,

modern medicine and technological innovation

is profoundly affecting

the very essence of what it means to look beautiful.

The universal nature of beauty is changing

even as we're changing the universe.

Thank you.

(Applause)