Final answer:
In Wason's 4-card task, flipping over the 7 confirms the rule 'if a card has a vowel on one side, it must have an even number on the other side' due to modus tollens.
Step-by-step explanation:
In Wason's 4 card task, you should flip over the 7 to confirm the rule "if a card has a vowel on one side, it must have an even number on the other side" because it follows modus tollens, which is a form of logical argument where the denial of the consequent leads to the denial of the antecedent. If we find that the 7, which is not an even number, has a vowel on the other side, it would directly contradict the rule, thereby disproving it. We are not confirming the rule, but we are checking for a possibility that could falsify it. Flipping over the 7 is a test to ensure that a card with an odd number does not have a vowel on the other side, which would invalidate the rule.