I continue my series of posts on mental shortcuts. It's probably a good idea to read my previous post.
Time to talk about a classic in my field: The "Linda Problem"
I have known Linda for a long time now. Let me tell you about her.
Linda is 31 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.
Consider the following eight statements about Linda.
___ 1. Linda is a teacher in elementary school.
___ 2. Linda works in a bookstore and takes Yoga classes.
___ 3. Linda is active in the feminist movement.
___ 4. Linda is a psychiatric social worker.
___ 5. Linda is a member of the League of Women Voters.
___ 6. Linda is a bank teller.
___ 7. Linda is an insurance salesperson.
___ 8. Linda is a bank teller who is active in the feminist movement.
I would like you to arrange the statements from the least likely to the most likely. It is easiest to put a number beside each statement. The least likely statement gets a 1 and the most likely statement gets an 8. I left a blank beside each statement in case you want to play along with a print out.
Did you give statement eight a higher number than statement six? In other words, did you rate statement eight as more likely than statement six? I did the first time I saw the problem. And most people do. But, as you probably guessed, that is wrong. Let's see those two statements again:
Linda is a bank teller.
Linda is a bank teller who is active in the feminist movement.
There cannot be more feminist bank tellers than there are bank tellers! So, it is impossible for the "bank teller feminist" statement to be more likely than the "bank teller" statement. How did you make this mistake? Here is my description of your thinking:
Linda was a philosophy major. She was outspoken. She was concerned about discrimination. Linda looks like a feminist. Her description is representative of a feminist. You used your representativeness shortcut. So, the feminist bank teller statement looked likely.
Linda's description is not representative of a bank teller. I certainly do not picture someone like Linda when I think of a bank teller!
You used your representativeness shortcut. So, the "Linda is a bank teller" statement did not seem likely. As a result, you rated the "Feminist bank teller" statement as more likely than the "bank teller" statement. You're in good company, remember. I did it too.
Hold on a Second!
At this point you might be saying to yourself, "Hold on a second! I thought Ian said I am pretty good at making my way through the world. And I am pretty good because I use mental shortcuts. But Ian's examples show how easy it is to make mistakes using shortcuts! Maybe I shouldn't use shortcuts. But, then what?" You are absolutely right. I have been showing you how your representativeness shortcut works by showing you how it can lead to mistakes. There is a method to my madness and I will let you in on my reasoning once we have considered another important mental shortcut. Stay tuned ...
For more writing by yours truly, visit me at My Bad Habits. I am also on Twitter.