# Idea [[Wason four-card selection task]] rule or [[logical implication]]: *If there is a vowel on one side of a card, then there is a an even number on the other side of the card*. Which of these four cards **need** to be turned in order to fully test that the rule applies? $v \rightarrow e$ ![[20231229115143.png]] Here, P represents a vowel, and Q represents an even number. The only false condition for the implication is when P is true and Q is false. Now let's consider each card using a [[truth table]]: ![[20231229121513.png]] **Card with a Vowel (E)**: This card needs to be turned over to check if the other side is an even number. This is because the rule directly states that a vowel must have an even number on the other side (the *second row* in the truth table where P is true and Q is false, which would make the implication false). Card with a Consonant (K): This card does not need to be turned over. The rule does not say anything about what should be on the other side if there's a consonant. Therefore, whatever is on the other side does not affect the truth of the rule (the *third and fourth rows* in the truth table, where P is false, the implication remains true regardless of Q). Card with an Even Number (4): Many people mistakenly think this card should be turned over, but according to the rule, it does not need to be. The rule specifies a condition for vowels, not numbers. An even number can have a vowel or a consonant on the other side without violating the rule (the *first and third rows* in the truth table, where Q is true, the implication remains true regardless of P). **Card with an Odd Number (7)**: This card needs to be turned over because if there's a vowel on the other side, the rule is violated. If there's a consonant on the other side, the rule holds. This checks for the case where P is true and Q is false, which is the only way the implication can be false (the *second row* in the truth table). In conclusion, you need to turn over the card with the vowel to see if it obeys the rule, and you need to turn over the card with the odd number to check if the rule is being broken. The card with the consonant and the card with the even number do not need to be turned over to test the rule's validity. # References