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Brain teaser to test your cognitive abilities…and biases

Posted Jul 11 2014 12:01pm

Please con­sider Linda, a 31-year-old woman, sin­gle and bright. When she was a stu­dent, in high school and in col­lege too, she was deeply involved in social jus­tice issues, and also par­tic­i­pated in environmental protests. Which is more prob­a­ble about Linda’s occu­pa­tion today?

a) Linda works as a TV reporter;

b) Linda is a bank teller;

c) Linda is a bank teller and active in the envi­ron­men­tal movement.


Quick, what’s your answer? a) or b) or c)? And in what precise order?


First, ignore how you ranked a), as it is irrelevant to this particular exercise. The key is this: If you ranked c) as more probable than b), you are wrong…and in very good com­pany. That’s what most of my Stanford col­leagues and I answered the first time we faced this teaser, and it reflects a very pervasive cognitive bias, technically called a “conjunction fallacy.”

Statistically speaking, by definition, it is more prob­a­ble that Linda is a bank teller, which is a whole cat­e­gory, that she is both a bank teller AND also active in the envi­ron­men­tal move­ment, which is a sub­set of that whole category.


To learn more about your brain and mind:

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