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.
Are there any areas of study that you feel are underrepresented here, and would be interesting and useful to lesswrongers?
I feel some topics are getting old (Omega, drama about moderation policy, a newcomer telling us our lack of admiration for his ideas is proof of groupthink, Friendly AI, Cryonics, Epistemic vs. Instrumental Rationality, lamenting how we're a bunch of self-centered nerds, etc. ...), and with a bit of luck, we might have some lurkers that are knowledgeable about interesting areas, and didn't think they could contribute.
Please stick to one topic per comment, so that highly-upvoted topics stand out more clearly.