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It's 1878.
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Sir Francis Galton
gives a remarkable talk.
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He's speaking to the anthropologic
institute of Great Britain and Ireland.
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Known for his pioneering work
in human intelligence,
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Galton is a brilliant polymath.
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He's an explorer,
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an anthropologist,
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a sociologist,
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a psychologist
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and a statistician.
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He's also a eugenist.
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In this talk,
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he presents a new technique
by which he can combine photographs
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and produce composite portraits.
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This technique could be used
to characterize different types of people.
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Galton thinks that if he combines
photographs of violent criminals,
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he will discover the face of criminality.
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But to his surprise,
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the composite portrait that he produces
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is beautiful.
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Galton's surprising finding
raises deep questions:
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What is beauty?
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Why do certain configurations of line
and color and form excite us so?
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For most of human history,
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these questions have been approached
using logic and speculation.
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But in the last few decades,
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scientists have addressed
the question of beauty
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using ideas from evolutionary psychology
and tools of neuroscience.
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We're beginning to glimpse
the why and the how of beauty,
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at least in terms of what it means
for the human face and form.
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And in the process,
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we're stumbling upon some surprises.
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When it comes to seeing
beauty in each other,
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while this decision is certainly
subjective for the individual,
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it's sculpted by factors that contribute
to the survival of the group.
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Many experiments have shown
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that a few basic parameters contribute
to what makes a face attractive.
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These include averaging, symmetry
and the effects of hormones.
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Let's take each one of these in turn.
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Galton's finding
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that composite or average faces
are typically more attractive
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than each individual face
that contributes to the average
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has been replicated many times.
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This laboratory finding fits
with many people's intuitions.
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Average faces represent
the central tendencies of a group.
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People with mixed features
represent different populations,
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and presumably harbor
greater genetic diversity
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and adaptability to the environment.
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Many people find mixed-race
individuals attractive,
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and inbred families less so.
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The second factor that contributes
to beauty is symmetry.
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People generally find symmetric faces
more attractive than asymmetric ones.
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Developmental abnormalities
are often associated with asymmetries,
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and in plants, animals and humans,
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asymmetries often arise
from parasitic infections.
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Symmetry, it turns out,
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is also an indicator of health.
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In the 1930s,
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a man named Maksymilian Faktorowicz
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recognized the importance
of symmetry for beauty
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when he designed the beauty micrometer.
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With this device,
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he could measure minor asymmetric flaws
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which he could then make up for
with products he sold from his company,
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named brilliantly
after himself, Max Factor,
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which, as you know,
is one of the world's most famous brands
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for "make up."
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The third factor that contributes
to facial attractiveness
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is the effect of hormones.
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And here, I need to apologize
for confining my comments
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to heterosexual norms.
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But estrogen and testosterone
play important roles
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in shaping features
that we find attractive.
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Estrogen produces features
that signal fertility.
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Men typically find women attractive
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who have elements
of both youth and maturity.
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A face that's too baby-like might
mean that the girl is not yet fertile,
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so men find women attractive
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who have large eyes,
full lips and narrow chins
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as indicators of youth,
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and high cheekbones
as an indicator of maturity.
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Testosterone produces features
that we regard as typically masculine.
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These include heavier brows,
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thinner cheeks
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and bigger, squared-off jaws.
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But here's a fascinating irony.
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In many species,
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if anything,
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testosterone suppresses the immune system.
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So the idea that testosterone-infused
features are a fitness indicator
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doesn't really make a whole lot of sense.
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Here, the logic is turned on its head.
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Instead of a fitness indicator,
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scientists invoke a handicap principle.
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The most commonly cited
example of a handicap
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is the peacock's tail.
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This beautiful but cumbersome tail
doesn't exactly help the peacock
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avoid predators
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and approach peahens.
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Why should such an extravagant
appendage evolve?
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Even Charles Darwin,
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in an 1860 letter to Asa Gray wrote
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that the sight of the peacock's tail
made him physically ill.
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He couldn't explain it
with his theory of natural selection,
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and out of this frustration,
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he developed the theory
of sexual selection.
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On this account,
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the display of the peacock's tail
is about sexual enticement,
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and this enticement means
it's more likely the peacock will mate
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and have offspring.
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Now, the modern twist
on this display argument
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is that the peacock is also
advertising its health to the peahen.
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Only especially fit organisms
can afford to divert resources
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to maintaining such
an extravagant appendage.
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Only especially fit men can afford
the price that testosterone levies
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on their immune system.
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And by analogy, think of the fact
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that only very rich men can afford
to pay more than $10,000 for a watch
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as a display of their financial fitness.
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Now, many people hear these kinds
of evolutionary claims
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and think they mean that we somehow
are unconsciously seeking mates
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who are healthy.
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And I think this idea
is probably not right.
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Teenagers and young adults are not exactly
known for making decisions
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that are predicated on health concerns.
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But they don't have to be,
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and let me explain why.
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Imagine a population
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in which people have three different
kinds of preferences:
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for green, for orange and for red.
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From their point of view,
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these preferences have
nothing to do with health;
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they just like what they like.
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But if it were also the case
that these preferences are associated
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with the different likelihood
of producing offspring --
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let's say in a ratio of 3:2:1 --
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then in the first generation,
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there would be 3 greens
to 2 oranges to 1 red,
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and in each subsequent generation,
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the proportion of greens increase,
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so that in 10 generations,
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98 percent of this population
has a green preference.
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Now, a scientist coming in
and sampling this population
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discovers that green
preferences are universal.
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So the point about this little
abstract example
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is that while preferences
for specific physical features
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can be arbitrary for the individual,
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if those features are heritable
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and they are associated
with a reproductive advantage,
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over time,
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they become universal for the group.
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So what happens in the brain
when we see beautiful people?
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Attractive faces activate
parts of our visual cortex
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in the back of the brain,
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an area called the fusiform gyrus,
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that is especially tuned
to processing faces,
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and an adjacent area called
the lateral occipital complex,
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that is especially attuned
to processing objects.
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In addition,
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attractive faces activate parts
of our reward and pleasure centers
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in the front and deep in the brain,
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and these include areas
that have complicated names,
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like the ventral striatum,
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the orbitofrontal cortex
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and the ventromedial prefrontal cortex.
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Our visual brain that is tuned
to processing faces
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interacts with our pleasure centers
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to underpin the experience of beauty.
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Amazingly, while we all
engage with beauty,
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without our knowledge,
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beauty also engages us.
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Our brains respond to attractive faces
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even when we're not thinking about beauty.
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We conducted an experiment
in which people saw a series of faces,
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and in one condition,
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they had to decide if a pair of faces
were the same or a different person.
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Even in this condition,
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attractive faces drove neural activity
robustly in their visual cortex,
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despite the fact that they were thinking
about a person's identity
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and not their beauty.
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Another group similarly found
automatic responses to beauty
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within our pleasure centers.
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Taken together, these studies suggest
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that our brain automatically
responds to beauty
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by linking vision and pleasure.
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These beauty detectors, it seems,
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ping every time we see beauty,
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regardless of whatever else
we might be thinking.
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We also have a "beauty is good"
stereotype embedded in the brain.
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Within the orbitofrontal cortex,
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there's overlapping neural activity
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in response to beauty and to goodness,
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and this happens even when people
aren't explicitly thinking
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about beauty or goodness.
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Our brains seem to reflexively
associate beauty and good.
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And this reflexive association
may be the biologic trigger
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for the many social effects of beauty.
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Attractive people receive
all kinds of advantages in life.
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They're regarded as more intelligent,
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more trustworthy,
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they're given higher pay
and lesser punishments,
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even when such judgments
are not warranted.
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These kinds of observations
reveal beauty's ugly side.
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In my lab, we recently found
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that people with minor facial
anomalies and disfigurements
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are regarded as less good, less kind,
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less intelligent, less competent
and less hardworking.
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Unfortunately, we also have
a "disfigured is bad" stereotype.
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This stereotype is probably
exploited and magnified
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by images in popular media,
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in which facial disfigurement
is often used as a shorthand
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to depict someone of villainous character.
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We need to understand
these kinds of implicit biases
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if we are to overcome them,
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and aim for a society
in which we treat people fairly,
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based on their behavior and not
on the happenstance of their looks.
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Let me leave you with one final thought.
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Beauty is a work in progress.
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The so-called universal
attributes of beauty
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were selected for during the almost
two million years of the Pleistocene.
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Life was nasty, brutish
and a very long time ago.
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The selection criteria
for reproductive success from that time
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doesn't really apply today.
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For example,
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death by parasite is not one
of the top ways that people die,
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at least not in the technologically
developed world.
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From antibiotics to surgery,
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birth control to in vitro fertilization,
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the filters for reproductive success
are being relaxed.
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And under these relaxed conditions,
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preference and trait combinations
are free to drift
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and become more variable.
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Even as we are profoundly
affecting our environment,
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modern medicine
and technological innovation
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is profoundly affecting
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the very essence of what it means
to look beautiful.
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The universal nature of beauty is changing
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even as we're changing the universe.
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Thank you.
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(Applause)