So I'm starting us out today
with a historical mystery.

In 1957, there were two young women,

both in their 20s,

both living in the same city,

both members of the same political group.

That year, both decided
to commit violent attacks.

One girl took a gun and approached
a soldier at a checkpoint.

The other girl took a bomb
and went to a crowded café.

But here's the thing:

one of the those girls
followed through with the attack,

but the other turned back.

So what made the difference?

I'm a behavioral historian,
and I study aggression,

moral cognition

and decision-making in social movements.

That's a mouthful. (Laughs)

So, the translation of that is:

I study the moment an individual
decides to pull the trigger,

the day-to-day decisions
that led up to that moment

and the stories that they tell themselves
about why that behavior is justified.

Now, this topic --

it's not just scholarly for me.

It's actually a bit personal.

I grew up in Kootenai County, Idaho,

and this is very important.

This is not the part of Idaho
with potatoes.

We have no potatoes.

And if you ask me about potatoes,

I will find you.

(Laughter)

This part of Idaho is known
for mountain lakes,

horseback riding,

skiing.

Unfortunately, starting in the 1980s,

it also became known
as the worldwide headquarters

for the Aryan Nations.

Every year, members of the local
neo-Nazi compound

would turn out and march through our town,

and every year,

members of our town
would turn out and protest them.

Now, in 2001, I graduated
from high school,

and I went to college in New York City.

I arrived in August 2001.

As many of you probably are aware,

three weeks later,

the Twin Towers went down.

Now, I was shocked.

I was incredibly angry.

I wanted to do something,

but the only thing that I could think
of doing at that time

was to study Arabic.

I will admit,

I was that girl in class
that wanted to know why "they" hate "us."

I started studying Arabic
for very wrong reasons.

But something unexpected happened.

I got a scholarship to go study in Israel.

So the Idaho girl went to the Middle East.

And while I was there,
I met Palestinian Muslims,

Palestinian Christians,

Israeli settlers,

Israeli peace activists.

And what I learned
is that every act has an ecology.

It has a context.

Now, since then, I have gone
around the world,

I have studied violent movements,

I have worked with NGOs
and ex-combatants in Iraq,

Syria,

Vietnam,

the Balkans,

Cuba.

I earned my PhD in History,

and now what I do is
I go to different archives

and I dig through documents,

looking for police confessions,

court cases,

diaries and manifestos of individuals
involved in violent attacks.

Now, you gather all these documents --

what do they tell you?

Our brains love causal mysteries,

it turns out.

So any time we see an attack on the news,

we tend to ask one question:

Why?

Why did that happen?

Well, I can tell you I've read
thousands of manifestos,

and what you find out is
that they are actually imitative.

They imitate the political movement
that they're drawing from.

So they actually don't tell us
a lot about decision-making

in that particular case.

So we have to teach ourselves
to ask a totally different question.

Instead of "Why?" we have to ask "How?"

How did individuals produce these attacks,

and how did their decision-making ecology
contribute to violent behavior?

There's a couple things I've learned
from asking this kind of question.

The most important thing is that

political violence is not
culturally endemic.

We create it.

And whether we realize it or not,

our day-to-day habits contribute
to the creation of violence

in our environment.

So here's a couple of habits
that I've learned contribute to violence.

One of the first things that attackers did

when preparing themselves
for a violent event

was they enclosed themselves
in an information bubble.

We've heard of fake news, yeah?

Well, this shocked me:

every group that I studied
had some kind of a fake news slogan.

French communists
called it the "putrid press."

French ultranationalists called it
the "sellout press"

and the "treasonous press."

Islamists in Egypt called it
the "depraved news."

And Egyptian communists called it ...

"fake news."

So why do groups spend all this time
trying to make these information bubbles?

The answer is actually really simple.

We make decisions based on
the information we trust, yeah?

So if we trust bad information,

we're going to make bad decisions.

Another interesting habit
that individuals used

when they wanted
to produce a violent attack

was that they looked at their victim
not as an individual

but just as a member of an opposing team.

Now this gets really weird.

There's some fun brain science behind
why that kind of thinking is effective.

Say I divide all of you guys
into two teams:

blue team,

red team.

And then I ask you to compete
in a game against each other.

Well, the funny thing is,
within milliseconds,

you will actually start experiencing
pleasure -- pleasure --

when something bad happens
to members of the other team.

The funny thing about that is
if I ask one of you blue team members

to go and join the red team,

your brain recalibrates,

and within milliseconds,

you will now start experiencing pleasure

when bad things happen
to members of your old team.

This is a really good example
of why us-them thinking is so dangerous

in our political environment.

Another habit that attackers used
to kind of rev themselves up for an attack

was they focused on differences.

In other words, they looked
at their victims, and they thought,

"I share nothing in common
with that person.

They are totally different than me."

Again, this might sound
like a really simple concept,

but there's some fascinating science
behind why this works.

Say I show you guys videos
of different-colored hands

and sharp pins being driven
into these different-colored hands,

OK?

If you're white,

the chances are you will experience
the most sympathetic activation,

or the most pain,

when you see a pin
going into the white hand.

If you are Latin American, Arab, Black,

you will probably experience
the most sympathetic activation

watching a pin going into the hand
that looks most like yours.

The good news is,
that's not biologically fixed.

That is learned behavior.

Which means the more we spend time
with other ethnic communities

and the more we see them as similar to us
and part of our team,

the more we feel their pain.

The last habit
that I'm going to talk about

is when attackers prepared themselves
to go out and do one of these events,

they focused on certain emotional cues.

For months, they geared themselves up
by focusing on anger cues, for instance.

I bring this up because
it's really popular right now.

If you read blogs or the news,

you see talk of two concepts
from laboratory science:

amygdala hijacking
and emotional hijacking.

Now, amygdala hijacking:

it's the concept that I show you
a cue -- say, a gun --

and your brain reacts
with an automatic threat response

to that cue.

Emotional hijacking --
it's a very similar concept.

It's the idea that I show you
an anger cue, for instance,

and your brain will react
with an automatic anger response

to that cue.

I think women usually get
this more than men. (Laughs)

(Laughter)

That kind of a hijacking narrative
grabs our attention.

Just the word 'hijacking"
grabs our attention.

The thing is,

most of the time, that's not really
how cues work in real life.

If you study history,

what you find is that we are bombarded
with hundreds of thousands of cues

every day.

And so what we do is we learn to filter.

We ignore some cues,

we pay attention to other cues.

For political violence,
this becomes really important,

because what it meant is that attackers
usually didn't just see an anger cue

and suddenly snap.

Instead,

politicians, social activists
spent weeks, months, years

flooding the environment
with anger cues, for instance,

and attackers,

they paid attention to those cues,

they trusted those cues,

they focused on them,

they even memorized those cues.

All of this just really goes to show
how important it is to study history.

It's one thing to see how cues operate
in a laboratory setting.

And those laboratory experiments
are incredibly important.

They give us a lot of new data
about how our bodies work.

But it's also very important to see
how those cues operate in real life.

So what does all this tell us
about political violence?

Political violence is not
culturally endemic.

It is not an automatic, predetermined
response to environmental stimuli.

We produce it.

Our everyday habits produce it.

Let's go back, actually, to those two
women that I mentioned at the start.

The first woman had been paying attention
to those outrage campaigns,

so she took a gun

and approached a soldier at a checkpoint.

But in that moment,
something really interesting happened.

She looked at that soldier,

and she thought to herself,

"He's the same age as me.

He looks like me."

And she put down the gun,
and she walked away.

Just from that little bit of similarity.

The second girl had
a totally different outcome.

She also listened
to the outrage campaigns,

but she surrounded herself
with individuals

who were supportive of violence,

with peers who supported her violence.

She enclosed herself
in an information bubble.

She focused on certain
emotional cues for months.

She taught herself to bypass certain
cultural inhibitions against violence.

She practiced her plan,

she taught herself new habits,

and when the time came,
she took her bomb to the café,

and she followed through with that attack.

This was not impulse.

This was learning.

Polarization in our society
is not impulse,

it's learning.

Every day we are teaching ourselves:

the news we click on,

the emotions that we focus on,

the thoughts that we entertain
about the red team or the blue team.

All of this contributes to learning,

whether we realize it or not.

The good news

is that while the individuals I study
already made their decisions,

we can still change our trajectory.

We might never make
the decisions that they made,

but we can stop contributing
to violent ecologies.

We can get out of whatever
news bubble we're in,

we can be more mindful
about the emotional cues

that we focus on,

the outrage bait that we click on.

But most importantly,

we can stop seeing each other
as just members of the red team

or the blue team.

Because whether we are Christian,
Muslim, Jewish, atheist,

Democrat or Republican,

we're human.

We're human beings.

And we often share really similar habits.

We have differences.

Those differences are beautiful,

and those differences are very important.

But our future depends on us
being able to find common ground

with the other side.

And that's why it is so, so important

for us to retrain our brains

and stop contributing
to violent ecologies.

Thank you.

(Applause)