Comment by etangent

It seems to me that the selection task is tricky because it concerns interpretation of language. "Every card that has a D on one side has a 3 on the other" makes a claim: that there is a directional dependency "D => 3" but it makes no claim that "3 => D". However the absence of the latter claim is not stated explicitly, it is supposed to be inferred from the original statement. The English language seems to lack a way to encode unambiguously the "A => B" relationship. So it should not be surprising that students used to looking out for language pitfalls when checking proofs also happen to be the students who do better on this task.