Transcriber: Lana Gonoratsky Reviewer: Maria K.
I want to read people's minds.
I want to know what people truly think.
And I am going to try, right now.
I see some people here who think, "Oh my god, can he really do that?"
I see someone here thinking, "That's amazing, the guy is French
but he can speak English! That's amazing!"
(Laughter)
Well, obviously I cannot read minds.
But there's something else I can do:
I can make people tell the truth.
And I'm going to show you how.
Maybe you don't see the point,
maybe you think people always tell the truth.
So let's try ...
I'd like you to raise your hand,
if your answer to the next question is yes.
Have you ever stolen office supplies from your employer?
So if yes, raise your hand.
Quite a few of you!
(Laughter)
Well, I have another question, which goes well here in a university,
and we know we have quite some students around.
Did you ever cheat on an exam when you were at school?
If yes, please raise your hand.
(Laughter)
Well, I did.
When I was seven, I copied one word from my neighbor,
because I could not remember how to write it.
And look at me now,
I'm trying to make it sound small.
I'm trying to look small, and if I could, invisible.
And I'm blushing.
Well, that's called shame.
And maybe, some of you did not raise your hand,
because you did not want to feel ashamed.
Well, we have many examples like that.
For instance, in political surveys, many people don't report
that they plan to vote for extreme political parties.
And we have surprises on election days.
So, survey companies correct for it because they know that people can lie.
Another example from medical sciences:
When studying sexually transmitted diseases,
it is important to understand people's sexual behaviour.
But you cannot observe it directly.
(Laughter)
You cannot be in people's bed or in people's kitchen,
or bathroom, or car, or wherever they might be doing it.
(Laughter)
So the only way to know is to ask.
And so for instance, asking: "Have you recently had unprotected sex
with an one-time partner?"
And many studies say that such behavior is under-reported.
We just don't know.
So imagine we run a campaign to promote the use of condom.
And we see that people report afterwards less unprotected sex.
Maybe they didn't change their behavior, but they simply feel more ashamed.
And they lied more.
We just don't know.
So surveys are used by governments, scientists, companies.
And many decisions and policies are based on those.
We don't know whether people are telling the truth;
we cross our fingers that they do.
But actually, we can do more.
We can use a truth serum.
I need a volunteer.
No, just kidding.
I'm not a doctor!
Well, I'm a doctor, but in economics.
I want to use an economic truth serum.
I'll reward you if you tell the truth.
Sounds much nicer, doesn't it?
So if people lie because of a feeling of shame,
then we can compensate this feeling and make them tell the truth.
We can transform the negative feeling of shame
into good feelings using money.
So, let's start with a very simple example.
Imagine I want to know your belief about the weather tomorrow.
Well, we can simply bet on it.
And for instance,
if you bet on rain and I take the opposite bet,
it reveals that you think rain is more likely than I think.
So bets reveal what we believe.
And maybe you often do that with people
when you disagree; you say, "Let's bet on it."
And that's a way to know whether people truly believe what they are saying.
You ask a question and you make people bet.
Bets are economic truth serums.
But so let's go back to the questions we were interested in,
like cheating or for instance, stealing office supplies.
Well, I cannot make you bet on it, because only you know whether you did it.
And I cannot reward truth-telling, if only you know whether you are lying.
So rewarding truth-telling in such cases seems impossible.
Well, there is a way.
And it all relies on one key intuition.
Here it comes.
There is a link between what you have done and what you think others have done.
It is a well established phenomenon in psychology
and I'm going to give you a couple of examples
coming from surveys my students conducted.
So some years ago, one of my students asked his colleagues, his fellow students,
whether they had ever cheated in an exam.
So, specifically copied from their neighbor.
And he also asked them to predict the rate of cheaters.
And I'm going to show you those predictions,
depending on whether people were cheaters themselves or not.
So cheaters predicted 65% of cheaters
and non-cheaters predicted only 47% of cheaters.
And the actual rate was 60%.
Another one of my students ran an anonymous survey in a public company,
asking people whether they had ever stolen office supplies.
And those ones that said "Yes," that they had stolen office supplies,
predicted 67% of "yes" answers.
While those ones that said, "No,"
predicted much less "yes" answers, only 24%.
And the actual rate was 54%.
So we use our own behavior to predict, to guess the behavior of others.
And it makes sense to do so.
It makes sense to use the one clear piece of evidence you have;
yourself.
And obviously, we're not stupid, we don't think everyone is like us.
We don't predict 100% of people behaving as we do.
But still, our expectations are influenced by our own behavior.
So I repeat the key intuition:
There's a link between what you have done and what you believe others have done.
Cheaters expect more cheaters than non-cheaters expect.
The next step will sound magical.
We are going to transform the key intuition into a truth serum.
And remember that a truth serum is just a bet.
So here it comes.
If you say that you are a cheater, then you should also bet
that there are more cheaters than predicted by the non-cheaters.
And that's all, nothing more.
We ask a question and we make you bet on the answers of others.
And for instance, betting on the rate of cheaters
is going to reveal whether you are a cheater yourself.
Sounds magical, doesn't it?
Well, the first one who established this result,
is an MIT professor, Drazen Prelec.
He published a paper in Science in 2004.
And it was a very beautiful, but some people would say
a bit complicated method.
So I worked and developed my betting version of it.
So in practice it means I designed the bets.
How much you bet, how much you get,
depending on your own answer and the answers of others.
So we can make people tell the truth, by asking them questions
and making them bet on the answers of others.
So now I'd like to finish this presentation with a Q & A.
But because I want to be sure that I know the answers,
I'm going to ask the questions myself, if you don't mind.
(Laughter)
So, the first question:
How does it work in practice?
Thank you very much, very nice question!
Well, it's simpler than you may think.
You ask questions like you would do in a regular survey,
and then you ask people to bet on the answers of others.
Then you connect all the data and you compute how much people win.
That's the mathematical part.
Afterwards you can reward people or if you want to preserve anonymity,
the money can be given to a charity.
And then it means that admitting the truth will imply more money for the charity,
which means a good deed.
So admitting the truth is a good deed.
A second question:
Can I use an economic truth serum
to find out whether my spouse is cheating on me?
Well I'm sorry, but no.
And there are two reasons for that:
First reason, we need to ask the question to more than one person,
and I guess you have only one spouse.
Second condition,
the people answering the question
should not feel any other negative consequences,
beyond the feeling of shame when answering.
But that's why in surveys we try to preserve anonymity.
But if you'd like, we could run an anonymous survey
to find out how many people in this room have ever cheated on their partner.
Shall we do that in the next break?
(Laughter)
Yes? No?
Last question: Why should we care about this method?
Well, it's a fair question.
And I told you we can use economic truth serum
to make people tell the truth.
But we can also motivate respondents with it.
In many surveys we have to fit in there's nothing to be ashamed of.
But the questions are just so boring.
And you may have had this experience in the past,
that you are asked to fill in a survey, you accept, you're a good citizen.
For the first couple of questions you think a bit about it
and then you just click through the rest.
Well, I sometimes do.
But the problem is that the answers you gave
are taken very seriously.
Some years ago, I filled in such a survey and some month later,
the university was implementing a new HR policy based on the survey.
And I thought, "Oh my god, I don't remember
what I had replied to that one."
So with an economic truth serum we can reward people for thinking,
for carefully considering their answers.
We say that surveys are used by companies, governments, scientists,
and by many of us when we decide, for instance, for whom to vote.
So with an economic truth serum, we can make sure that our decisions
are based on accurate descriptions of reality.
And not on lies or just on random clicks.
So here, at Erasmus University, together with my team,
I'm working on developing new, simpler economic truth serums.
I cannot read minds, yet.
But I can make people tell the truth.
Thank you.
(Applause)