Wason Selection Task

The Wason selection task is a classic logic puzzle used in the psychology of reasoning to demonstrate the prevalence of Confirmation Bias.

The Task

Participants are presented with four cards, each with a number on one side and a letter on the other. For example:

[4] [7] [E] [K]

They are then given a rule to test, such as: "If a card shows an even number on one face, then its opposite face is a vowel."

The question is: Which card or cards must you turn over to prove the rule true or false?

The Common Error & Insight

Most people correctly choose the [4] card. They also incorrectly choose the [E] card. This is the confirmation bias at work—they are trying to confirm the rule. Turning over the [E] card doesn't help; if the other side is an odd number, it doesn't violate the rule.

The logically correct answer is to turn over the [4] and the [K].

• The [4] tests the first part of the rule.
• The [K] (a consonant) tests the second part (the contrapositive). If the other side of the [K] is an even number, the rule is definitively proven false.

The task reveals our deep-seated tendency to look for confirming evidence rather than the potentially falsifying evidence that is crucial for sound logical reasoning.

Tags: #psychology #cognition #logic #reasoning #bias #confirmation-bias #wason-selection-task