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# Take the world’s shortest IQ test!

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The Cognitive Reflection Test (CRT), developed in 2005 by psychologist and Yale School of Management professor Shane Frederick, is the world’s shortest IQ test, comprised of only three questions.

In a paper published in The Journal of Economic Perspectives, Frederick explains that he picked the three questions because they were all “found to yield impulsive erroneous responses” — the questions make it easy for people to quickly jump to conclusions. In other words, the CRT was designed to test your ability to ignore your intuitive gut response and think more rationally.
After you’ve taken the test, scroll down for the answers.
No cheating!!!

## Here Are the Questions

1. The Bat and Ball Problem
A bat and a ball together cost \$1.10. The bat costs \$1 more than the ball. How much does the ball cost?
2. The Widget-Making Machine Problem
If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?
3. The Size-Double Lily Pad Patch Problem
There is a patch of lily pads in a lake. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half the lake?
Scroll down for the answers to the questions.
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1. The ball costs 5 cents.
You probably guessed 10 cents, didn’t you? A ball that costs 5 cents plus a bat that costs \$1.05 will set you back \$1.10. And \$1.05 is exactly \$1 more expensive than 5 cents. A Princeton study found that people who answered 10 cents were significantly less patient than those who got it correct.
2. It would take 100 machines 5 minutes to make 100 widgets.
Your gut might tell you the answer is 100 minutes. From the question, we know that it takes 5 minutes for 1 machine to make 1 widget. Thus, it would take 5 minutes for 100 machines to make 100 widgets. (Check out a similar, if not more difficult problem, here.)
3. The lily pads would cover half the lake in 47 days.
You might have guessed 24 days. It seems intuitive to halve the number of days because you’re halving the size of the lilypad patch. But if the area of the lake covered in lilypads doubles every day, it would only take one day for it to go from being half covered to fully covered. Take one day away from 48 days and you’re left with 47. (We have a similar problem here, too.)
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Before introducing the test to the world in 2005, Frederick tested the CRT on 3,428 respondents in 35 separate studies over a 26-month period beginning in January 2003. Only 17% of students from the top universities in the world (like Yale and Harvard) got a perfect score. People who score high are less vulnerable to biases in thinking.

## So how did you do?

H/t FOTM‘s josephbc69