Today, in the palm of your hand,

you have access to a world of information.

You can reach a multitude of new sources

and exchange your views
with a wide range of people

all over the world.

This new reality should allow us 
to share a wisdom,

to communicate, to understand each other

and to become more understanding 
of our differences,

more tolerant of our differences.

But 2016 seems to have replaced
the information age

with the post-truth era.

With Brexit and the Trump election,

we have found, we have discovered,

that more communication 
doesn't mean more information.

Let me show you what I mean.

Here is a picture of the 
Trump inauguration ceremony in 2017,

and the same picture of the 
Obama inauguration ceremony in 2009.

The White House declared
that the Trump ceremony

had been the largest in history.

Did you know

that 28% of Trump supporters

said they believed there were 
as many people, if not more,

at the Trump ceremony.

30% said they didn't know. 
They were not sure.

And 41%, that is less than half,

said that they disagreed 
with the White House statement.

When you see these pictures, 
these views may seem crazy.

So how is it that people can believe 
something so clearly untrue?

But wait a minute,

Are you sure that you would never 
believe something so clearly untrue?

Think about it.

These pictures are not proof.

They could have been photoshopped.

They could have been swapped.

So when somebody raises
these doubts to you,

you will have to use your own judgment

to weigh the evidence
and make up your mind.

So now suppose that you were
a Trump supporter.

Are you sure

that you would not give any credence

to somebody raising these doubts?

Are you sure that you
would never entertain

that perhaps there were more people 
at the Trump ceremony,

and that these pictures are not proof?

Today, I want to put to you

that the cause of the fake news success
lies primarily with us.

Fake news works

because we are willing to believe it.

And because we are willing to believe it, 
we lie to ourselves.

If we want a sound public debate,

we need to stop lying to ourselves
when we engage with the news.

Let's consider an ideal public debate,

and think about it as a battle of ideas.

All ideas are voiced and debated.

A good idea is convincing,
and it wins over less convincing ideas.

The philosopher Karl Popper

said that this process
should lead public debate

to select the best ideas.

Unconvincing ideas disappear, 
and only the good ones survive.

And science seems like a perfect example

where public debate
leads to selection of the best ideas.

With this view in mind,

the Internet should have 
a positive effect on public debate.

On the Internet, ideas are free 
to be voiced and criticized.

Good ideas should be able to convince 
more people and spread around,

and bad ideas are abandoned.

But when you look,

that's not necessarily what is happening
on the Internet at the moment.

So why is that?

Well, perhaps, this view 
of the public debate is a bit unrealistic.

In 1949, Max Planck famously joked 
about this vision from Popper.

Max Planck was a theoretical physicist 
who eventually won a Nobel Prize.

He said,

"A new scientific truth doesn't triumph
because it convinces its opponents;

rather, these opponents get old,

and eventually they die,

and they are replaced by 
a new generation of scientists."

And what Max Planck 
was alluding to with irony

was to the reality of debates
with humans, us.

Us humans, we are not designed 
as perfect rational thinkers

only looking for the truth.

The fact is that often, 
we are attached to our ideas.

We can be attached to ideas

because some ideas
may be convenient for us -

for interest.

So going to the example 
of the scientists of Max Planck,

these scientists may have become famous

because of the ideas
that they proposed in the past,

and which are now old ideas.

Abandoning these ideas would be
losing part of the credit they got

for proposing these ideas 
in the first place.

But it's not just in science.

If you think of politics,

if a government proposes
to extend social welfare,

those who would receive social welfare

have an interest to believe 
it's good for the country.

And those who would have to pay
for the social welfare

have an interest to think 
it's bad for the country,

it's a bad policy for the country.

But we are not just attached to ideas
for material interests;

it's much more complex.

Often, we can be 
emotionally attached to our ideas.

They may be part of our identity.

So if I'm a Christian conservative
or a left-wing liberal,

these ideas may be part of who I am.

Abandoning these ideas 
could be losing part of my identity.

As a consequence,
we are attached to our ideas.

So we're not neutral judges

when we're considering 
the evidence for or against them.

On the contrary, 
science and behavior

show that we typically 
engage in self-deception,

which means that we are
building beliefs which are compatible

with our interests 
and with our other beliefs.

Self-deception is subtle,

it takes place all the time
in your everyday life.

So I'm going to give you two ways

in which self-deception
can change what we believe in

and produce convenient
views for ourselves.

First, when you receive some news,

you have some flexibility 
in how you consider it.

If it's positive news
which is compatible with your beliefs,

you can accept it as positive evidence.

And if it's negative news,

you can to the contrary
choose to discount it

and not choose to consider it.

Let me tell you about a study.

A group of people 
were asked about beliefs,

political beliefs 
and non-political beliefs.

For their political beliefs,
they had to say

whether they believed in statements
such as "Abortion should be legal" -

very loaded statements,
typical of political statements.

And non-political beliefs 
were statements such as

"Second-hand smoking
is dangerous to your health."

So what happened is

that these people were confronted
with contradictions to these beliefs.

What do you think people did?

How did they react when they were 
confronted with these contradictions?

Well, here's how people reacted
with their non-political beliefs.

So you have the strength of their beliefs
before the contradiction and after it.

So when faced with a series
of contradictions,

they updated their beliefs

and the strength of their beliefs
was lower after facing contradictions.

But now look at what happened

when they were faced with contradictions
to their political beliefs.

Here you can see that people resisted 
the contradiction much more

and held to their political beliefs.

That's one way we selectively
interpret the news.

But there is another way.

We're not just receiving the news; 
we're looking out for it.

We are selecting where we want 
to look for information.

And typically, we look for
confirming information.

If you are a conservative,

you are more likely
to read a conservative newspaper,

to watch a conservative news channel,

and perhaps even to turn off
the TV or the radio

when a left-wing politician 
is being interviewed.

Let me show you a hypothetical scenario.

Let's say that you wake up in the morning
and you open your newspaper,

and in one scenario,

you've got some news which is not good -

it's a contradiction to your beliefs.

Let's say that this news suggests
that your favorite politician

is involved in a political scandal.

And consider the other situation, 
where to the contrary,

the news in the newspaper is positive -
it goes with your usual beliefs.

Perhaps it's another politician, 
a politician you do not like,

who is involved in the political scandal.

Do you think, do you feel,

that you'd react in the same way
to these two situations?

Well, research shows that you would not.

Most likely, what happens
is that if you find a contradiction,

you tend to look for all the news sources.

You give yourself a chance
to find something

which will contradict this negative news.

Perhaps another newspaper,

perhaps you will read
the fine print in the newspaper

to make sure that the title
was really reflecting the information.

On the contrary, 
if you have the positive news,

you're more likely to stop there,

you're more likely to be happy to consider
that this piece of evidence

is enough for you to make up
your mind on this issue.

So as much as we would like to think
of ourselves as rational thinkers,

it is a fact that this tendency 
to look for confirming news

and to reject negative information 
is ingrained in us.

So now before you panic

and you think that our irrationality
is making public debate impossible,

you can relax.

These bars have existed forever, 
way before social media.

So what's happening with social media

is that they are exacerbating 
some of the effects of these bars.

Let me give you two ways 
in which they are doing so.

First, on the Internet 
you have much more freedom

to look for the information 
which is convenient

to whatever beliefs you have.

The Internet is like a giant supermarket.

For any kind of idea,

you'll be able to find arguments for 
and supporting this idea.

Let's consider a crazy idea as an example.

Let's consider that you believe 
that the Earth is flat.

Well, 30 years ago,
you would have been a bit alone

and maybe struggling to find people
to give you evidence for this.

Today, you can just 
connect to the Internet,

contact the Flat Earth Society,

and this society is going to provide you 
with elements of evidence,

arguments in favor of your belief.

That's another way

in which the Internet helps you
engage in self-deception,

that you can do it collectively.

You now have a multitude
of communities on the Internet

that have created
informational bubbles on their own.

In these bubbles, 
people select information,

interpret information,
and repackage it

in a way that is compatible 
with the community's views.

When a new fact is discussed 
in this community,

the images which are positive 
for the community are reinforced,

and those which are not are dropped,

and the nuances are lost.

These communities build simple views

compatible with the beliefs
of the community.

So the social media have not created 
a unified public space

where ideas are debated;

instead, social media have increased 
our ability to connect specifically

with the people whose views 
mostly match our own.

And whatever your views,

you can find a community
of like-minded people

with whom you can share arguments
supporting your existing beliefs

and not challenging them.

But what do you want?

Do you want a unified public space 
where ideas are debated, discussed,

and where maybe the best ideas can win,

or a compartmented public space

where different visions of the world 
can coexist unchallenged?

Well, if we want to defend and support

the existence of an open public space,

we need to realize
that the problem starts with us,

with how we form opinions

and how we share them on the social media.

So perhaps, in the post-truth era 
we need some guidelines

about how to interact on the social media.

Here are three steps.

Step 1:

Avoid the narrow selection of information
which closely match your views.

Make sure that in your timeline

you've got some news sources 
which challenge your view.

Try to find people with whom you disagree

and exchange with them.

Listen to what they have to say.

Try to appreciate the points 
that they may have.

Give them a chance to change your mind.

Point 2:

Question your views.

The more you'd like an idea to be true,

the more you need to distrust the way
you made up your mind about it.

Are you sure that you considered

all the best counterarguments
to the views you have?

that you've considered the possibility
of weak points in your reasoning?

Try to find them.

Whenever you really want 
an idea to be true,

you may remember
that at some point in your life,

we all liked to believe in Santa.

And even though we really wanted
Santa to be true,

it didn't make it more real in the end.

So the more you'd like an idea to be true,

you need to be wondering,
Is it too good to be true?

Do I believe this 
because I want to believe it

or because of the evidence?

Could it be another Santa for me?

Step 3:

Avoid contributing
to the distortion of facts.

When you want to forward
information on social media,

make sure you've read it,
you understand it,

and avoid simplifying it in a way

which is going to conform
with the views of the community.

Try not to contribute
to an echo chamber effect

within the community of views
you are participating in.

If you follow these guidelines, 
you are going to do yourself a favor:

you're going to stop building
a convenient alternative reality;

you're going to avoid spreading 
half truths and distorted facts;

and you will limit the self-enforcing 
groups of confirming exchanges,

which are pushing people 
in different informational bubbles.

You will help ideas 
to be questioned and challenged,

and you will contribute to making
the public space an open space

where the best ideas can win.

Will you allow yourself 
to change your views

and to abandon old ones?

Smart people change their mind.

Choose to be one.

(Applause)