Full transcript of the episode (it gives away every surprise)
Question for the reader
A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost?
That’s not it.
The ball costs 5 cents, and the bat $1.05. If the ball cost 10 cents, the bat would cost $1.10, and the total would be $1.20.
Who Decides?
You think you know the reasons for your choices. Your brain makes them up after the fact.
You have two ways of thinking.
One is fast, automatic, intuitive: it blurted out “10 cents” before you even decided anything. The other is slow, laborious… and lazy. It only wakes up if it gets shaken.
Daniel Kahneman spent his life mapping the traps of fast thinking, with his friend Amos Tversky. In 2002, he received the Nobel Prize in Economics: a psychologist, honored for showing that we are not the rational calculators of the textbooks.
Question for the reader
A TV game show. Three doors: behind one, a car; behind the other two, a goat. You pick a door. The host, who knows everything, opens another door: a goat. He offers you the chance to switch. What do you do?
- I switch doors (correct answer)
- I keep my door
- It makes no difference: it’s fifty-fifty
If you answer “I switch doors”:
That’s the right answer. But do you know why? Play to see for yourself.
If you answer “I keep my door”:
That’s what almost everyone answers. And it’s wrong. Don’t take my word for it: play.
Interactive experiment
The three doors
Play a few games, sometimes switching doors, sometimes not. Then let the computer play a thousand.
The reader plays the three-door game as many times as they like; the table compares their wins depending on whether they switched doors or not. A simulation of a thousand games shows that switching wins about two times out of three.
Switching doors doubles your chances.
Two chances out of three if you switch, one out of three if you stay. Yes, really.
In 1990, the American columnist Marilyn vos Savant published this answer in a magazine. She received some 10,000 letters, nearly a thousand of them signed by PhDs, explaining that she was wrong.
Paul Erdős, one of the greatest mathematicians of the century, was only convinced after seeing a computer simulation.
The trick: the host knows where the car is, and never opens that door. Your first choice had one chance in three of being right; it still does.
The other two doors shared two chances out of three between them. By eliminating one of them, the host concentrated those two chances on the last one.
Interactive experiment
The wheel of fortune
Spin the wheel. Then answer a question that has nothing to do with it.
The reader spins a numbered wheel, then estimates the percentage of African countries among the members of the United Nations. The wheel is rigged: it only stops on 10 or on 65.
The wheel was rigged.
It could only stop on 10 or on 65. In the original experiment, those who had seen 10 answered 25%; those who had seen 65, 45%. The correct answer is 28%: 54 countries out of 193.
A number drawn at random, completely unrelated to the question, pulled your answer like a magnet. This is the anchoring effect, one of the best-established biases in psychology.
Experience is no protection. In 2006, German judges rolled loaded dice before sentencing in a fictitious case. When the dice came up 9, they handed down nearly 8 months; when they came up 3, just over 5 months.
All right: our calculations are biased. But at least we know why we hold our opinions. Let’s test that.
Interactive experiment
Your opinions
Six statements. For each one, say whether you agree. There is no right answer, and nothing leaves your browser.
The reader gives their opinion on six statements. They are then shown a summary of their answers, in which two opinions have been secretly reversed, and asked to justify those two.
You defended an opinion that wasn’t yours.
You found reasons to justify it. Like seven participants out of ten in the original study.
In 2005, in Sweden, Petter Johansson and Lars Hall showed volunteers two photos of faces: “Which one do you find more attractive?” Then, with a sleight of hand, they handed them the photo they had not chosen, and asked them why.
Most noticed nothing and justified their “choice.” One participant explained that he liked the young woman’s earrings. The one he had actually chosen wasn’t wearing any.
Neurologists already knew about this talent. In some epileptic patients, the two halves of the brain are separated surgically. A chicken claw is then shown to the left half, the one that speaks, and a snowy landscape to the right half, which doesn’t.
The left hand picks a shovel. Why a shovel? Without hesitating, the left half, which never saw the snow, makes something up: “To clean out the chicken shed.”
The interpreter. A part of your brain constantly makes up reasons for what you do, even when it doesn’t know the real causes. It isn’t lying: it believes them. And so do you.
So should we distrust our emotions, and decide with reason alone? In the 1980s, the neurologist Antonio Damasio followed a patient he called Elliot. A tumor had damaged part of his frontal cortex.
His intelligence was intact. So was his memory. But his emotions had almost died out.
Elliot had become unable to decide. Choosing between two dates for an appointment took him half an hour of arguments for and against. Sorting documents: by date, by size, by importance? The whole afternoon went by.
He lost his job, then his marriage.
Without emotions, reason spins its wheels.
Emotions don’t sabotage your decisions: they make them possible, by giving each option its weight.
“The heart has its reasons, which reason does not know.”
Your eyes, your memory, your choices: everything goes through an inner narrator who improvises. But who is this narrator? Where are you, in all of this? In the next episode, you are going to lose a face… and gain a nose.
Sources
- Shane Frederick, “Cognitive reflection and decision making,” Journal of Economic Perspectives, 2005.
- Daniel Kahneman, Thinking, Fast and Slow, 2011.
- Marilyn vos Savant, “Ask Marilyn,” Parade, 1990; Paul Hoffman, The Man Who Loved Only Numbers, 1998.
- Amos Tversky and Daniel Kahneman, “Judgment under uncertainty: heuristics and biases,” Science, 1974.
- Birte Englich, Thomas Mussweiler and Fritz Strack, “Playing dice with criminal sentences,” Personality and Social Psychology Bulletin, 2006.
- Petter Johansson et al., “Failure to detect mismatches between intention and outcome in a simple decision task,” Science, 2005.
- Lars Hall, Petter Johansson and Thomas Strandberg, “Lifting the veil of morality: choice blindness and attitude reversals on a self-transforming survey,” PLoS ONE, 2012.
- Michael Gazzaniga, The Social Brain, 1985; Who’s in Charge?, 2011.
- Antonio Damasio, Descartes’ Error, 1994.