The “bat and ball” question is the “iconic” question in the Cognitive Reflection Test (CRT) introduced by the behavioural economist Shane Frederick in 2005.[1]
How much does the ball cost?[2]
An intuitive answer of 10 cents springs immediately to mind, but a moment’s reflection leads to the realisation that if the ball costs 10 cents then the bat costs $1.10, which would result in a total of $1.20 for both, not the $1.10 stated in the question. The correct answer to the price of the ball – 5 cents – can be worked out by trial and error or simple algebra.[a]The question can be recast in the form of two simultaneous equations:
Adding those two equations tells us that two bats cost $2.10. So one bat costs $1.05, which means that the ball costs 5 cents.
This question, like the others in the CRT, was designed to elicit an erroneous intuitive response that can be recognized as incorrect on reflection and then corrected.[3] Adults with higher CRT scores have been found to be better at rejecting unsubstantiated claims, including fake news and paranormal beliefs.[3]
The test has its roots in the various dual-process models of human information processing proposed by psychologists during the 1980s and 1990s, exploring aspects of decision making and the formation of social attitudes and stereotypes. The most influential of those theories is the elaboration likelihood model,[4] but what they all have in common is the idea that there are two information processing systems in play:[5]
- System 1, executed quickly without much reflection
- System 2, more deliberate, requiring conscious thought and effort
The tendency not to override the intuitive response is known as miserly processing.[1]