Cognitive reflection test
The cognitive reflection test (CRT) is a task designed to measure a person's tendency to override an incorrect "gut" response and engage in further reflection to find a correct answer. It was first described in 2005 by psychologist Shane Frederick. The CRT has a moderate positive correlation with measures of intelligence, such as the Intelligence Quotient test, and it correlates highly with various measures of mental heuristics.
Later research showed that the CRT is a multifaceted construct: many start their response with the correct answer, while others fail to solve the test even if they reflect on their intuitive first answer. It has also been argued that suppression of the first answer is not the only factor behind the successful performance on the CRT: numeracy and reflectivity both account for performance.
Basis of test
According to Frederick, there are two general types of cognitive activity called "system 1" and "system 2." System 1 is executed quickly without reflection, while system 2 requires conscious thought and effort. The cognitive reflection test has three questions that each have an obvious but incorrect response given by system 1. The correct response requires the activation of system 2. For system 2 to be activated, a person must note that their first answer is incorrect, which requires reflection on their own cognition.
The test has been found to correlate with many measures of economic thinking, such as numeracy, temporal discounting, risk preference, and gambling preference. It has also been correlated with measures of mental heuristics, such as the gambler's fallacy, understanding of regression to the mean, the sunk cost fallacy, and others.
Keith Stanovich found that cognitive ability is not strongly correlated with CRT scores because it will only lead to better CRT performance under certain conditions. First, the test-taker must recognize the need to override their system 1 response, and then they must have available cognitive resources to carry out the override. If the test-taker does not need to inhibit system 1 for the override, then the system 2 response immediately follows. Otherwise, they must have the capacity to sustain inhibition of system 1 in order to engage the system 2 response.
Test questions and answers
The original test penned by Dr. Frederick contained only the three following questions:
- 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? _____ cents
- If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets? _____ minutes
- In a lake, there is a patch of lily pads. Every day, the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half of the lake? _____ days
The answers are: 5 cents, 5 minutes, and 47 days.
Limitations and alternatives
Studies have estimated that between 44 and 51% of research participants have previously been exposed to the CRT. Those participants that are familiar with the CRT tend to outscore those with no previous exposure, which raises questions about the validity of the measure in this population. In an effort to combat limitations associated with familiarity, researchers have developed a variety of alternative measures of cognitive reflection. Recent research, however, suggests that the CRT is robust to multiple exposure, so that despite the raw score increases in experienced participants, its correlations with other variables remain unaffected 
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