Author: Peter Wason

Peter Wason (1924 – 2003) was a cognitive psychologist who pioneered the Psychology of Reasoning. He progressed explanations as to why people make certain consistent mistakes in logical reasoning. He designed problems and tests to demonstrate these processes, such as the Wason selection task and the 2-4-6 problem. He also coined the term "confirmation bias".

“If there is a vowel written on one side of a card, then there is an even number written on the other side.”
How many of these four cards do you need to flip in order to check the validity of this sentence?

What would the answer be if you know that each card contains one letter and one number?

You need to flip all cards except for the second one. If each card contains one letter and one number, then you need to flip only A and 7.