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Psychologists Don't Know Math

Posted by Zonk on from the one-plus-one-equals-your-mother dept.

stupefaction writes "The New York Times reports that an economist has exposed a mathematical fallacy at the heart of the experimental backing for the psychological theory of cognitive dissonance. The mistake is the same one that mathematicians both amateur and professional have made over the Monty Hall problem. From the article: "Like Monty Hall's choice of which door to open to reveal a goat, the monkey's choice of red over blue discloses information that changes the odds." The reporter John Tierney invites readers to comment on the goats-and-car paradox as well as on three other probabilistic brain-teasers."

3 of 566 comments (clear)

  1. Re:Hmmm.... by B3ryllium · · Score: 0, Redundant

    Please enlighten me as to how they botched the Monty Hall problem.

  2. Re:Inaccurate? by Fred+Ferrigno · · Score: 0, Redundant

    As someone who majored in psychology, worked in two labs, and read countless psychology papers, I can tell you that 99% of psychologists avoid math when possible, and the other 10% try to use it but make obvious errors. Please tell me that's a joke.
  3. Re:Hmmm.... by AaxelB · · Score: 0, Redundant

    Wait, are you trying to say that your problem is just like the Monty Hall problem (because it's not)? Or is it just an unrelated misleading-probability riddle?

    Either way, the problem is that X is a random variable, and the expected value calculation depends on X, making what you have simply nonsense. If you defined the amount in the smaller envelope as X (not a random variable), you stand to either gain X or lose X by switching. The expected value of switching would be 0.5*X + 0.5*(-X) = 0.