The Cognitive Reflection Test (CRT)


Here the 3-item CRT test for ‘cognitive reflection’ developed at Princeton. Average Carnegie Mellon and Harvard undergraduate scores for this test range from 1.4-1.5 out of 3! The answers can be found in the comments below. Please add your own comments letting others know how you got on with this test.


Cognitive Reflection Test (CRT)

Are you ready….

Take your time…


(1) A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball.
How much does the ball cost? _____ cents


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


(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? _____ days


The Cognitive Reflection Test has a large correlation with IQ. But it is designed to measure the tendency to override automatic problem solving responses that are incorrect and to use your meta-awareness to double check your thoughts and find the correct response. For this reason, how people do on the CRT can be a good predictor of how well people do in overcoming cognitive biases – of which there are many that we may be susceptible to on a day-by-day basis (Ref).


If you are interested in using meta-awareness & other strategies to augment IQ and help with cognitive biases, sign up to the free content below:


I am a cognitive scientist with a joint Ph.D in cognitive psychology and neuroscience from the Center of the Neural Basis of Cognition (Carnegie Mellon/Pittsburgh). At IQ Mindware we develop brain training interventions to increase IQ, critical thinking, decision making, creativity and executive functioning.


  • 1) 5 cents
    2) 5 minutes
    3) 47 days

    3 out of 3, and I’m just 17 years old!!!!!!!!!!!!!!!!!!!

    Gaetano 20.05.2012
  • 1) 10 cents
    2) 5 min
    3) 47 days

    Too easy, sorry.

    Andy 20.05.2012
  • The ball costs 10 cents. 100 machines will make 100 widgets in 5 minutes. It will take 47 days to cover half the lake with lily pads. I had to slow down and read the questions, because my first thoughts were to quick and then I would catch myself and then I would see the true answer.
    I probably should have given myself a little more time to wake up completely.
    Good Day
    Gerald Peatross

    Gerald Peatross 20.05.2012
  • Yes, I love these brain openers!
    My problem is,I , many times, when I guess wrong, I can never find the logic of what I did wrong or the correct route to the winning answer.
    I know there is a pattern to take to reach the correct answer, but I am lost on how to find it.

    I’m talking about those “matrix “[?] games] The one where you have 4 patterns [or 3] across and 3 or 4 vertical patterns. Example.

    Tom Wilson 20.05.2012
  • 5 cents, 5 minutes, 47 days…

    well over 85% of respondents (including Harvard and Yale grads, and a less % of MIT grads) think the ball will cost 10 cents (wrongo dongo), so don’t feel too bad if you missed that one, the correct answer is 5 cents…

    other two are no-brainers…

    Duncan 22.05.2012
  • too bad you are wrong!

    Duncan 24.05.2012
  • 1)10 cents
    2)5 min
    3)24 days

    Thomas 13.07.2012
  • 5 cents, 5 min, 47 days. easy peasy.

    Chris Tapp 20.11.2012
  • 3

    tj 09.09.2015
  • Thomas you got it Wrong it was superbly easy
    1)5 cents
    2)5 minutes
    3)47 days
    It’s Funny because I am only twelve years old and half of Harvard or Carnegie got it wrong so Im proud of myself

    Bill James 21.12.2015
  • Ball is 5 cents

    Bill James 21.12.2015
  • the ball costs 5 cents

    abby 04.02.2016
  • I am 99% sure you looked at the comments

    Bob 16.01.2017
  • It’s 5 cents, 5 mins, and 47 days, sorry!

    Kam 16.01.2017
  • Lol I’m fifteen and got them
    -5 min
    -47 days
    Not too hard lol

    Isabella 12.02.2017
  • -5 cents
    -5 minutes
    –47 days
    Too easy for a fifteen year old.

    Fur Que 25.03.2017
  • Me too, but i’m 13

    Christian Kurtz 27.03.2017
  • 5 cents, 5 minutes, 47 days.

    I’m a ramblin’ wreck from Georgia Tech and a hell of an engineer!

    How did the MIT (the Georgia Tech of the north) grads do?

    Brett 06.05.2017
  • Cant make sense of the bat and ball, the other two make sense. Can anyone explain it to me?

    Andrew 06.05.2017
  • 5 cents

    Anonymous 06.05.2017
  • “A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball.”

    Ball = X
    Bat = X + $1.00

    Thus, if X = $0.05, then X + $1.00 = $1.05

    Therefore, the Ball costs $0.05
    and the bat costs $1.05
    and the total cost is $1.10

    Ken 09.05.2017
  • The bat costs a dollar more than the ball so the total cost is the cost of one ball plus the cost of a ball plus a dollar. So $1.10 = $1 plus the cost of two balls. So $0.10 is the cost of two balls.

    Michael Price 09.05.2017
  • $1.05 – $.05 = $1.00

    Dean 09.05.2017