The Answer to Pop Quiz #1

The results are in for our inaugural Pierian Puddle pop quiz.

The question was:

"A bat and a ball cost $1.10. A bat costs $1 more than a ball. So how much does a ball cost?"

The results were mixed. We had one correct answer, one smart-arse answer, and one incredibly wrong answer. However, the answer that we didn't get at all, was the answer that most participants gave in a recent study using this question (Frederick, 2005).

Most people, it seems, give the incorrect answer '10 cents'; indeed, that was my first answer too.

But think about it. If the ball costs $0.10, and the bat "costs $1 more than the ball", then the bat must cost $1.10. Together that equals $1.20, not $1.10. So the right answer is that the ball must cost "5 cents".

It took me ages to work that out. I was so sure that "10 cents" was the answer. Indeed, according to the author of the study, most people get this question wrong because the intuitive answer ("10 cents") comes so easily to mind -- $1.10 splits so easily into $1 and $0.10. Because it seems so easy, most of us fail to carefully vet the logic of our answer.

So to those of you who got the question right, it might suggest that you are quite cognitively reflective -- you rationally think through things and don't succumb to the intuitive answer.

References

Frederick, S. (2005). On the ball: Cognitive reflection and decision-making. Journal of Economic Perspectives.