Prediction

Some unorthodox moves are wrong only in the textbook. Others are good only because nobody expects them. The difference decides how often to make them.

Ask someone to recall a list of words they heard a few minutes ago and they will often hand back a word that was never on it.

You can sing a song you know from the first line without trying. Ask yourself to start at the second verse and something odd happens: you go back and run up to it. That small detour is the best clue to what knowing a song is.