I wanted to save the world and then make everyone happy.

But I knew that I'd need superpowers

to make my dreams come true.

So I used to embark on these imaginary journeys

to find intergalactic objects from planet Krypton,

which was a lot of fun,

but didn't get much result.

When I grew up and realized

that science fiction was not a good source for superpowers,

I decided instead to embark on a journey of real science,

to find a more useful truth.

I started my journey in California

with a UC Berkley 30-year longitudinal study

that examined the photos of students

in an old yearbook

and tried to measure their success and well-being

throughout their life.

By measuring their student smiles,

researchers were able to predict

how fulfilling and long-lasting

a subject's marriage will be,

how well she would score

on standardized tests of well-being

and how inspiring she would be to others.

In another yearbook, I stumbled upon Barry Obama's picture.

When I first saw his picture,

I thought that these superpowers came from his super collar.

But now I know it was all in his smile.

Another aha! moment

came from a 2010 Wayne State University research project

that looked into pre-1950s baseball cards

of Major League players.

The researchers found

that the span of a player's smile

could actually predict the span of his life.

Players who didn't smile in their pictures

lived an average of only 72.9 years,

where players with beaming smiles

lived an average of almost 80 years.

(Laughter)

The good news is that we're actually born smiling.

Using 3D ultrasound technology,

we can now see that developing babies appear to smile,

even in the womb.

When they're born,

babies continue to smile --

initially, mostly in their sleep.

And even blind babies smile

to the sound of the human voice.

Smiling is one of the most basic, biologically-uniform

expressions of all humans.

In studies conducted in Papua New Guinea,

Paul Ekman,

the world's most renowned researcher on facial expressions,

found that even members of the Fore tribe,

who were completely disconnected from Western culture,

and also known for their unusual cannibalism rituals,

attributed smiles to descriptions of situations

the same way you and I would.

So from Papua New Guinea

to Hollywood

all the way to modern art in Beijing,

we smile often,

and you smile to express joy

and satisfaction.

How many people here in this room

smile more than 20 times per day?

Raise your hand if you do. Oh, wow.

Outside of this room,

more than a third of us smile more than 20 times per day,

whereas less than 14 percent of us

smile less than five.

In fact, those with the most amazing superpowers

are actually children,

who smile as many as 400 times per day.

Have you ever wondered why being around children

who smile so frequently

makes you smile very often?

A recent study at Uppsala University in Sweden

found that it's very difficult to frown

when looking at someone who smiles.

You ask, why?

Because smiling is evolutionarily contagious,

and it suppresses the control

we usually have on our facial muscles.

Mimicking a smile

and experiencing it physically

help us understand whether our smile is fake or real,

so we can understand the emotional state

of the smiler.

In a recent mimicking study

at the University of Clermont-Ferrand in France,

subjects were asked to determine

whether a smile was real or fake

while holding a pencil in their mouth

to repress smiling muscles.

Without the pencil, subjects were excellent judges,

but with the pencil in their mouth --

when they could not mimic the smile they saw --

their judgment was impaired.

(Laughter)

In addition to theorizing on evolution in "The Origin of Species,"

Charles Darwin also wrote

the facial feedback response theory.

His theory states

that the act of smiling itself

actually makes us feel better --

rather than smiling being merely a result

of feeling good.

In his study,

Darwin actually cited a French neurologist, Guillaume Duchenne,

who used electric jolts to facial muscles

to induce and stimulate smiles.

Please, don't try this at home.

(Laughter)

In a related German study,

researchers used fMRI imaging

to measure brain activity

before and after injecting Botox

to suppress smiling muscles.

The finding supported Darwin's theory

by showing that facial feedback

modifies the neural processing

of emotional content in the brain

in a way that helps us feel better when we smile.

Smiling stimulates our brain reward mechanism

in a way that even chocolate --

a well-regarded pleasure inducer --

cannot match.

British researchers found that one smile

can generate the same level of brain stimulation

as up to 2,000 bars of chocolate.

(Laughter)

Wait. The same study found

that smiling is as stimulating

as receiving up to 16,000 pounds Sterling in cash.

That's like 25 grand a smile.

It's not bad.

And think about it this way:

25,000 times 400 --

quite a few kids out there

feel like Mark Zuckerberg every day.

And, unlike lots of chocolate,

lots of smiling can actually make you healthier.

Smiling can help reduce the level

of stress-enhancing hormones

like cortisol, adrenaline and dopamine,

increase the level of mood-enhancing hormones

like endorphin

and reduce overall blood pressure.

And if that's not enough,

smiling can actually make you look good

in the eyes of others.

A recent study at Penn State University

found that when you smile,

you don't only appear to be more likable and courteous,

but you actually appear to be more competent.

So whenever you want to look great and competent,

reduce your stress

or improve your marriage,

or feel as if you just had a whole stack of high-quality chocolate --

without incurring the caloric cost --

or as if you found 25 grand in a pocket

of an old jacket you hadn't worn for ages,

or whenever you want to tap into a superpower

that will help you and everyone around you

live a longer, healthier, happier life,

smile.

(Applause)