When they do aircraft certification tests, are all the passengers briefed as per a normal briefing? If so, perhaps it would be interesting to brief half of them beforehand and not do an in-cabin briefing to simulate real life a bit better as half the passengers would be ignorant of what to do?
Yes they are briefed but of course they all know what they are going to do so are fully mentally prepared.
Take my advice always try and sit by an emergency exit, I always do.