I learnt a long time ago by a director (CEO) of a large UK company on how to assess people, their technical abilities and personality and that is to act stupid

I learnt a long time ago by a director (CEO) of a large UK company on how to assess people, their technical abilities and personality and that is to act stupid/ daft - not just one question, but for periods of time. and see how they respond to you a very effective technique when dealing or interacting with so called Subject Matter Experts. If they're an expert they should be able to explain complex stuff at a High/ medium/ low levels or just say they do not know. If they're not really an expert then they cover up their lack of knowledge