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The card trap

A classic trap was used by Wason and Johnson-Laird (1972).

Four cards are laid out as below:




E




K


4


7


The conditional statement is now given: 'If a card has one vowel on one side, then it has an even number on the other side.'

The question is to decide which are the minimum cards that need to be turned over to prove that the conditional statement is true.

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Without going in search of the answer, what do you think?
1 2
Comments  
Hi,

Two. (E and 4).

Clive
CliveHi,

Two. (E and 4).

Clive

Interesting.

"To affirm the antecedent, E is correct. E is a vowel and thus should have an even number on the other side. If there was an odd number on the other side, the statement would be false, so E must be turned over to check for this.

But choosing 4 is affirming the consequent. Even though 4 is even, it can have a vowel or consonant on the other side and the statement is not falsified."
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Note that Clive's answer ("two") is not incorrect, given the form of the original question. "Minimum" should be omitted.

MrP
MrPedanticNote that Clive's answer ("two") is not incorrect, given the form of the original question. "Minimum" should be omitted.

MrP

Yes, I wasn't too happy about that "minimum". Anyway, what's your solution to the question?
I don't get it. You just turn over the only one with the vowel (E), don't you?
But where is the rest of the deck? The card with A or I? Don't you need to look on the other side of all the ones with vowels to be sure?
So maybe the answer is 5 - for the 5 vowels.
Or maybe I didn't understand the question.

Anyway, interesting, but where's the linguistics question?
CJ
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CalifJimAnyway, interesting, but where's the linguistics question?
CJ

Did you miss it?
"Only 4% said E and 7. The 7 could deny the consequent and hence must be checked. If there was a vowel on the other side, the statement would be false.

So what?

Be careful about if-then statements, both in your own use and in those that others use. It does, of course also mean that you can make statements that are logically false and few people will challenge you."
CalifJimOr maybe I didn't understand the question.

CJ

Maybe the "minimum" confused you.

<The question is to decide which are the minimum cards that need to be turned over to prove that the conditional statement is true.>

Is that supposed to be the "minimum number of cards" or "the minimum card numbers and letters"? I feel it's the latter.
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