The Cognitive Reflection Test (CRT), the world’s shortest IQ test, challenges takers with just three questions to reveal if they outperform 80% of the population in reasoning.
Developed in 2005 by psychologist Shane Frederick of the Yale School of Management, the CRT predicts susceptibility to common thinking errors. Studies over two decades, involving thousands of college students, show fewer than 20% answer all three correctly.
Recent social media buzz has amplified its reach, with one TikTok breakdown garnering 14 million views.
Question 1: Bat and Ball
A bat and a ball cost $1.10 total. The bat costs $1.00 more than the ball. How much does the ball cost?
Most intuitively guess $0.10 for the ball, but the correct answer is $0.05. This makes the bat $1.05—exactly $1 more—and totals $1.10.
Frederick’s original MIT study tested 3,428 participants, mainly from MIT, Princeton, and Harvard. Published in the Journal of Economic Perspectives, it found only 17% correct across all questions, highlighting cognitive reflection as a key intelligence marker akin to SAT performance.
Question 2: Machines and Widgets
If five machines take five minutes to make five widgets, how long for 100 machines to make 100 widgets?
The common error is 100 minutes, but the answer is five minutes. Each machine produces one widget in five minutes, so 100 machines complete 100 widgets simultaneously in that time.
Question 3: Lily Pads
A lake’s lily pad patch doubles daily. It covers the lake in 48 days. When does it cover half?
Intuitive answers suggest 24 days, but exponential growth means 47 days. On day 47, it reaches half; day 48 doubles to full coverage.
A 2011 Memory & Cognition study of 346 U.S. and Canadian freshmen found just 6.6% perfect scores. Conversely, a 2016 Judgment and Decision Making analysis reported 41.3% success among 395 Iranian students.
Social media debates persist. One viral thread exceeding 5.5 million views featured claims like, “The bat costs 1.50, the ball costs .50. You get them both for 1.10.” Another user mocked, “The math ain’t mathing.” On the widgets question, reactions included, “Lmao everyone thinks it’s 5 minutes,” with replies insisting it is.
The CRT mirrors standardized tests by probing reflective thinking over snap judgments.
