Can You Pass The World's Shortest IQ Test? It's Just Three Questions Long, But Few Can Get Them All Right


The Cognitive Reflection Test (CRT) has been hailed as the world's shortest IQ test. Apparently, it only takes three questions to separate the Einsteins from the Homer Simpsons of this world.

The quiz, developed in Princeton in 2005 by psychologist Shane Frederick, is designed to test your ability to ignore your gut response and think slower and more rationally. Or in psychology-speak, how good are you at ignoring system 1 (intuition) thinking in favor of system 2 (analytic) thinking? To succeed in the CRT, you must spend time reflecting on your answer and question your intuitive response. 

Of course, to prove your genius you must get all three questions correct but speed also matters. Speedier answers is another sign of a higher IQ.

So, how smart are you really? Remember, the questions might not be quite as simple as they first seem. Even students at some of the world's top universities (including Yale and Harvard) failed to get all three answers correct in a 2003 study. In fact, only 17 percent achieved a perfect score. 

The Quiz

1. A bat and a ball cost $1.10 in total. The bat costs $1 more than the ball. How much does the ball cost?

2. If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?

3. In a lake, there is a patch of lily pads. 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 of the lake? 

Scroll down for the answers!














The Answers

  1. 1. 5 cents – There's a very good chance you guessed 10 cents. The answer is actually a little less – a 5 cent ball plus a bat costing $1.05 will set you back $1.10. And, of course, $1.05 is exactly $1 more expensive than 5 cents. (A Princeton study found that people who responded 10 cents were "significantly" less patient than those who got the right answer.)
  1. 2. 5 minutes – Your gut instinct might be to say 100 minutes. Fortunately, it wouldn't take quite so long. From the question, we can determine it takes exactly 5 minutes for 1 widget machine to make 1 widget. Therefore, it would take 5 minutes to make 100 widgets from 100 widget machines.
  2. 3. 47 days – You might have guessed 24 days. It seems intuitive to half 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. 




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