“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?”
What was your first response to the question?
Many people say that the ball costs 10 cents. Although this is often the first intuitive response, it is not correct. If the ball cost 10 cents and the bat costs $1.00 more than the ball, then the bat would cost $1.10 and the total would be $1.20.
The correct answer to this problem is that the ball costs 5 cents and the bat costs $1.05, totalling thus $1.10.
Our brains tend to simplify things and place too much faith in our intuitions. Psychologist Daniel Kahneman explains that many people find cognitive effort at least mildly unpleasant and avoid it as much as possible, so they tend to trust their intuitions instead.