I would expect it to be extremely hard. I do not limit the scope of these tests to simple paper question and answer. I would be ok if an MRI was needed, for the teste not to know the test was about rationality, if it required a group of well trained actors to fool the teste, or a virtual simulation(within todays technology). Of course tests that can be used/verified immediately by users are preferable.

In the end the techniques required may be prohibitive, but at least it would make known what techniques/technologies to watch/promote for the future.