Thinking fast and slow chapter 15. Linda: less is more

Following the schedule of our reading calendar

The first time I read about Linda experiment I felt like Carlos when evaluating Tom W. problem. It was like: Come on! Everybody knows that being a bank teller is more probable than being a bank teller AND blah, blah, blah. People participating in the experiment have misunderstood “more probable” with “more plausible” or something alike. “Probable” is not a well defined word and people tend to guess what the problem is really about by taking clues on what information is given.

One has to be very critical with experiments like those. Piaget the psychologist thought that children under the age of four didn’t possess the concept of number, and had this elegant experiment to prove it. He showed four years old kids two set of marbles, distributed like this:

1) o o o o o o

2) o    o      o         o
When asked in which row there were more marbles most children choose the second row. So, according to Piaget, four year old children confuse quantity with occupying space. The more space you cover the more elements you have

Decades later, other psychologists replicated the experiment but with an interesting twist. Instead of marbles they used sweets. So when asked in which row there were more sweets, they still choose row 2, but, when invited to choose one row and get all the sweets in that row, guess what? They all choose row 1.

So the kids did know the concept of number. They just didn’t understood the question.

Nevertheless after reareading this chapter I found the experiment on people being older than 55 and having heart attacks, and the numbers of errors decreased highly if instead of talking about percentages, one was asked about 100 people, I’m not sure what to say. If such a small change transforms results so greatly, maybe this is system one getting in the way of system 2.

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2 thoughts on “Thinking fast and slow chapter 15. Linda: less is more

  1. My thoughts on this issue right now are going this way:

    I you show a picture to 100 people and ask what it shows and 92 of them say: “a dog” and a group of linguists meet in a congress and decide that the right word to define that picture is “table”, what would you conclude?
    a) Most English speakers don’t know what a dog is.
    b) These linguists are a bunch of over-educated idiots.
    I stay with b.

    This is the same case. If most English speakers say that “the probability of Linda being a feminist layer is higher than that of being a layer” then, the word “probability” in English has to mean something compatible with this answer. Speakers define the meaning of words in his language not PhDs living of taxpayer money.

    If there is another language called Statisticianish, where “probability” means another thing. And if you want the answer in Statisticianish the you have to make the question in Statisticianish:

    “Let’s call L the set containing all the lawyers in America and let’s call LF the subset of L containing…”

    Then the listener knows that you are not talking English and begins to think in statistical terms. And here, yes, the statisticians make the rules and most people can be wrong.

    I have the intuition that
    a) The probability of Linda being a feminist lawyer is higher than that of being a lawyer
    b) The people that think like this are majority
    c) The people that think like that are doing better in life outside academia (we should test it)
    d) Most of real problems that you can encounter in real life if you think a) are when dealing with formal systems that work with the statistical definition of probability: academia, exams, insurance contracts, banking, finance …
    e) Given a Random event called E, the probability of E belonging to L is higher or equal than the probability of E belonging to FL. Because, obviously, FL is a subset of L.

  2. Couldn’t agree more with you Carlos. That’s exactly the problem. “Probable” has several meanings, and it is stupid to insist that we should use only the mathematical one.
    An indirect evidence of that is that when people are told the “solution” to the problem they don’t feel like -oh! Of course, silly me! -as in the vast majority of examples in this book so far. Instead, they feel from molest to outraged because they feel like the experimenter cheated on them.

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