1. Wason and Johnson-Laird (1972)
Confirmation Bias
The Wason Card Problem
Wason and Johnson-Laird (1972)

2. Confirmation Bias
Each card has a number on one side and a letter on the other.
You can turn over 1 or 2 cards.
Which card / cards would you turn over to prove the following statement false?
“If a card has a vowel on one side, it has an even number on the other”.

3. Confirmation Bias
“If a card has a vowel on one side, it has an even number on the other”.
1 card?
2 cards?

4. Confirmation Bias
“If a card has a vowel on one side, it has an even number on the other”.
Choose a Combination
A and D?
D and 4?
D and 7?
4 and 7?
A and 4?
A and 7?

5. Confirmation Bias
By selecting only one card you can only confirm the statement.
As you will recall, the objective was to falsify it…
Return

6. Confirmation Bias
Selecting this combination means you have confirmed the statement.
Which is good.
The downside here is that your task was to select cards to falsify the statement…
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7. Confirmation Bias You have not chosen a vowel.
These cards, therefore, cannot falsify the original statement.
Return

8. Confirmation Bias
This selection cannot falsify the original statement because you have not chosen a vowel.
Return

9. Confirmation Bias
This selection cannot falsify the original statement because you have not chosen a vowel.
Return

10. Confirmation Bias
By selecting these cards you have confirmed the statement.
You can take some comfort in the fact this was likely to be the most popular choice among your peers.
You are not, in all probability, alone.
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11. Confirmation Bias
“If a card has a vowel on one side, it has an even number on the other”.
The only card combination that can be used to prove this statement false is:
A + 7

12. Confirmation Bias ShortCutstv The Wason Card Problem Wason and
Wason and
Johnson-Laird (1972)
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