Another tricky question

In which we learn how our cognitive and psychological processes trip us up again.

Hi, meet Sienna she is 26 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations.



Having read this which of these statements do you think is most likely to be true?

A Sienna works in a bank.

B Sienna works in a bank and is active in the feminist movement.

Did you answer A? Well clever you that's correct but most people go for answer B. It 'feels' like B should be more probable but it can't be at most it can only have the same chance as A.

Lets imagine there are a thousand people like Sienna and all of them work in a bank, even if 999 of them are also active in the feminist movement the odds of being in the bank and a feminist are still less than working in a bank alone. I know some of you will still be unsatisfied so go here for a longer explanation about the probabilities. This error is formally called the conjunction fallacy.

A very similar experiment to the one above was carried by Amos Tversky & Daniel Kahneman 40 years ago. In that study 85% of college students thought B was more likely. When they repeated it with the more simple example above (the previous one had lots of options you had to rank) roughly the same amount got it wrong. When they gave the complex version to statisticians the error rate was just as high but with the simple one they did better. 

This isn't very reassuring because the real world is complex, not simple. This means even 'experts' are prone to this cognitive bias. 

This is another example of our 'gut' quick and dirty cognitive processes giving us a wrong answer. It is not hard to see how these assumptions could impact negatively in criminal justice settings, health and even our personal interactions.

What's the good news, well as usual just being aware of these processes going on gives you a chance to engage your 'head' and try to avoid making the same mistake again. This process of challenging automatic thoughts is part of the concept of cognitive behavioural therapies.