Social Psychology Network

Maintained by Scott Plous, Wesleyan University

Answer to the Four-Card Task

The correct answer is A and 7.

Explanation:    The only way to falsify an "if X, then Y" statement ("if vowel, then even number") is by finding an instance of "X and not Y" ("vowel and odd number"). D and 4 are irrelevant, because these cards cannot combine a vowel and odd number.

Card with A Card with D
 
Card with 4

Card with 7

Key Finding:    When Wason and his colleague Johnson-Laird put this type of question to 128 university students, they found that "A and 4" was the most common response (given by 59 people), and "A" was the next most common (given by 42). In other words, students chose the cards capable of confirming the statement rather than disconfirming it. The tendency to seek out confirming evidence is known as a "confirmation bias."

Reference:    Wason, P. C., & Johnson-Laird, P. N. (1972). Psychology of Reasoning: Structure and Content. Cambridge, MA: Harvard University Press.

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