Boxing in, by bracketing. People who claim to have no idea about a quantity will often give surprisingly tight ranges when explicitly interrogated.
And most of the time their original “no idea” will be more accurate than the stuff you made them make up.
I do think there’s a rationality skill implicit in the text: the “coaching” that witnesses undergo to avoid giving answers they don’t want to give. That’d be worth learning, as it’s literally defense against the dark arts. And the test for it could be an interrogation of the kind that you describe.
And most of the time their original “no idea” will be more accurate than the stuff you made them make up.
I do think there’s a rationality skill implicit in the text: the “coaching” that witnesses undergo to avoid giving answers they don’t want to give. That’d be worth learning, as it’s literally defense against the dark arts. And the test for it could be an interrogation of the kind that you describe.