The reflex answer, and the pause that beats it
A bat and a ball cost Rs 110; the bat costs Rs 100 more. Almost every brain shouts Rs 10, and almost every brain is wrong.
Your fast system offers the first answer that fits the shape of the question.
Your slow system can check it, but only if you give it a moment.
People who pause five seconds beat most adults on these. The pause is the skill.
Then and now
Since 2005 the CRT became one of the most studied tests in judgment research; the modern finding is that the PAUSE is a skill separate from intelligence.
Frederick, S. (2005)
Where it began“Cognitive Reflection and Decision Making”
Journal of Economic Perspectives, 19(4), 25-42
Introduced the three-question Cognitive Reflection Test (the bat-and-ball among them); resisting the first answer predicts better decisions.
Toplak, M. E., West, R. F. and Stanovich, K. E. (2011)
State of the art“The Cognitive Reflection Test as a predictor of performance on heuristics-and-biases tasks”
Memory and Cognition, 39, 1275-1289
The CRT predicts resistance to a wide range of reasoning traps better than raw cognitive ability does: reflection is its own skill.
What we do and do not claim
The bat-and-ball is a famous test of reflection, not of IQ. We use it to train the pause, never to label a child.