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 emphasize."
Thank you.
(Applause)