While I can't necessarily provide any facts, I am pretty sure that those who say "yes" when they are cornered like that, are the ones who won't actually do it. While those who say "no" are the ones that are more likely to let the guard down at the time of indoctrination and they will be way to deep in by the time they realize what they are being asked to do.
It is a simple question in plain sight, however, most do not consider that such command (to drink the poison) will never come out of the blue or will never be as obvious as you put it to your wife. The people of Jonestown trained periodically with fake suicide drills before the actual act happened. So it is easy to answer either way, but the truth won't really come out until you are the crossroad.