How to do spot an insanely intelligent person from the one who is just plain crazy? At what moment you decide on terminating further business talks over still trying to find a common ground? Obviously, people have different personalities (and it’s crucial for company growth to hire mix of different personalities). At best, after a first weird encounter you may just assume that that person is an extreme introvert/extrovert (the opposite of you), which used to work in different environment. But when do you recognise, that that person is just out of touch with the reality?