These two Nazi scientists worked
at the Dachau Concentration Camp

during World War II.

They were conducting an experiment

to see how long a human being
could survive in freezing water.

Like good scientists,

they took systematic measures
including duration until death.

Examples of human cruelty
of this kind raise a big question.

How is it possible
to treat a person as a mere object?

The traditional explanation
for human cruelty is in terms of evil.

I find the concept of evil
unhelpful and unscientific.

It implies that the person is possessed
by some supernatural force.

Even worse it's dangerously circular;

if the definition of evil
is the absence of good,

then all we're really saying

is he did something bad
because he is not good.

It hasn't really taken us
any further forward.

In contrast the concept of empathy,

I'm going to argue
is scientifically helpful;

you can measure it, you can study it.

Empathy has two distinct components --
cognitive and affective.

Cognitive empathy is the ability

to imagine someone else's
thoughts and feelings;

putting yourself into
someone else's shoes.

It's the recognition part.

Affective empathy is the drive to respond
with an appropriate emotion

to what someone else
is thinking or feeling.

I'm going to argue
that low affective empathy

is a necessary factor
to explain human cruelty.

Empathy isn't all or none;
it comes by degrees,

and there a individual differences in it.

So it gives rise
to the empathy bell curve.

Most of us are in the middle
of this spectrum

with average amounts of empathy.

There are some people
who have above average levels of empathy.

But what are the factors

that can lead an individual
to have low empathy

either temporarily or permanently?

What are those social factors?
What are those biological factors?

One social factor
is obedience to authority.

The experiment by Stanley Milgram
at Yale University showed

that people are willing to administer
electric shocks to someone

to help them learn,

if they're instructed to do so
by an authority figure.

This suggests that simply,

following orders may be one factor
that can erode our empathy.

A second social factor is ideology.

When the terrorists flew the planes
into the World Trade Center on 9/11,

Ww have to assume

that they were in the grip
of a strongly-held belief

that they were doing the right thing.

Of course, we don't know

whether the terrorists
who signed up for that action

had low empathy to begin with,

but it's possible

that their ideological beliefs
were another factor

that could erode
their empathy for their victims.

A third social factor 
is in-group/out-group relations.

In Rwanda, we saw one ethnic group
used propaganda

to stereotype the out-group;

describing them as subhuman
and as cockroaches.

When we dehumanize a group as the enemy,

we have the potential to lose our empathy;

and we saw the catastrophic genocide

that ensued.

But none of these social factors
can explain individuals like Ted Bundy.

He started his adult career
as a psychology student

of the University of Washington

where he volunteered
on a telephone helpline

and persuaded women to meet him.

And over the successive years,

he committed rape and murder
of at least 30 women.

We can assume that he had
good cognitive empathy

because he was able 
to deceive his victims,

but that he lacked affective empathy
- he just didn't care -

and he lacked it in enduring ways.

The evidence that psychopaths
like Ted Bundy lack affective empathy

comes from an experiment by James Blair

that was conducted in Broadmoor Hospital.

He showed psychopaths and a control group

three different types of images,

threatening images, neutral images,
and images of people in distress.

What he found was that the psychopaths

only showed reduced physiological response

when they saw the images
of people in distress.

So this suggests that they lacked
affective empathy.

People with autism have difficulties
with cognitive empathy.

They struggle to imagine
other people's thoughts,

their motives, their intentions,
and their feelings.

But people with autism
don't tend to hurt other people;

instead, they are confused by other people

and withdraw socially, preferring
the more predictable world of objects.

People with autism
have intact affective empathy

because when they hear
that somebody is suffering

it upsets them.

This leads us to imagine

that people with autism
and psychopaths are mirror opposites.

The psychopath has good cognitive empathy
- that's how they can deceive -

but they have reduced affective empathy.

People with autism
have intact affective empathy,

but struggle with cognitive empathy
for neurological reasons.

Psychopaths don't come out of nowhere.

Many of them have shown

antisocial behavior 
and delinquency in their teens.

John Bowlby at the Tavistock Clinic
in London studied delinquents and found

that many of them had experienced
emotional neglect in early childhood.

He argued that the absence
of parental love in early childhood

is another factor
that can erode your empathy.

But we know that early experience
can't be the whole story

because not everyone
who has a bad childhood

loses their empathy.

Avshalom Caspi at the Institute
of Psychiatry in London showed

that if you've experienced
severe maltreatment in childhood

that increases your risk of delinquency.

But your risk of deliquency
goes up even more

if you also a carrier
of one version of the MAO-A gene

shown here in red;

so genes and environment interact.

Another biological factor

that is associated with empathy levels
is the hormone testosterone.

In the fetus, testosterone
shapes brain development.

We've measured testosterone

in the amniotic fluid
that surrounds the baby

in women who are having 
amniocentesis during pregnancy.

We then wait for the baby to be born,
and we follow up the children.

When the children were eight years old,

we asked them which word best describes

what the person in the photo
is thinking or feeling.

Here the correct answer is
he is interested in something.

What we found was that the higher
the level of fetal testosterone,

the more difficulties the child was having

at this test of cognitive empathy.

How much empathy we show
is a function of the empathy circuit;

a network of regions in the brain.

Here we can look at just two of them:

in red, for left ventromedial
prefrontal cortex,

and in blue, the amygdala.

This is Phineas Gage 
who suffered damage

to his left ventromedial prefrontal cortex

after dynamite blasted a metal rod
up behind his eye and through his brain.

Before the accident, he was described
as a polite, considerate individual.

After the accident,
he was described as rude

and no longer able to judge

what was socially appropriate
for different situations.

He'd lost his cognitive empathy.

Jean Decety at the University of Chicago
used brain scanning

- functional magnetic resonance imaging -

to look at the teenage delinquent brain

whilst they were watching films
where somebody experiences pain

such as when this piano player's fingers
got crushed by the lid of the piano

falling down on his fingers.

What he found was that teenagers
with delinquency didn't show

the typical levels of activity
in the amygdala --

part of the empathy circuit in the brain.

But let's not forget
the positive side of empathy.

Most of us have enough empathy,

and some people
have high levels of empathy.

When these two men formed a relationship

based on mutual respect and on empathy,

it let to the end of apartheid
in South Africa.

Empathy is vital for a healthy democracy;

it ensures that we listen
to different perspectives,

we hear other people's emotions,
and we also feel them.

Indeed without empathy,
democracy would not be possible.

I met this two women
in Cambridge this week

when they came to visit.

On the left is Siham,
and she is a Palestinian woman;

her brother was shot
and killed by an Israeli bullet.

On the right is Robi;
she is an Israeli woman.

Her son was killed
by a Palestinian bullet.

These two women
have taken the courageous step

of forming a relationship
across the political divide.

They haven't given in
to the emotion of revenge

which would simply perpetuate
the cycle of violence.

Instead, they've used their empathy
to recognize that they both share

the same sorrow, the same awful pain
of having lost a loved one.

Empathy is our most valuable
natural resource for conflict resolution.

We could wait for our political leaders

to use empathy
- and that would be refreshing -

but actually, 
we could all use our empathy.

As Siham and Robi told me,

"The conflict won't stop
until we empathize."

Thank you.

(Applause)