ask questions twice in quick succession, forwards then backwards. you should get a forwards then backwards answer and these answers should be complementary. if the answers are the same, if you get no answer or feel physiological changes inside the person as they answer, there is a problem. Not necessarily a lie or dishonesty, but the person is on some level aware they are not being completely honest.
the question then, is always why.
i’ve found mountains and anthills, as well as anthills perceived as mountains, mountains perceived as anthills.