**It may be ranked as the university with the best academic reputation in the world, but the majority of Harvard students are still flummoxed by a simple logic puzzle.**

In fact, according to psychologist Daniel Kahneman's book *Thinking Fast and Slow*, more than half of students at leading universities struggle with it - and that figure rises to above 80 per cent at "less selective" institutions.

**See how you get on:**

A bat and ball cost £1.10.

The bat costs one pound more than the ball.

How much does the ball cost?

**What is your answer?**

**Scroll down for the correct answer**

**The answer is: 5p**

As Kahneman explains:

A number came to your mind. The number, of course, is 10: 10p. The distinctive mark of this easy puzzle is that it evokes an answer that is intuitive, appealing, and wrong. Do the math, and you will see. If the ball costs 10p, then the total cost will be £1.20 (10p for the ball and £1.10 for the bat), not £1.10. The correct answer is 5p. It is safe to assume that the intuitive answer also came to the mind of those who ended up with the correct number — they somehow managed to resist the intuition...

Many people are overconfident, prone to place too much faith in their intuitions. They apparently find cognitive effort at least mildly unpleasant and avoid it as much as possible.

*Correction: This post initially said that the "bat costs one dollar more than the ball". It should have read "one pound". (It wasn't a trick question!). Thanks to the readers who pointed out our mistake, and apologies for any confusion.*

**More: The optical illusion that confuses adults - but not children**