As a counterpoint, I can distinguish a very bad chess player from a good one without seeing a single game he/she has played. Just looking at his/her behavior an

As a counterpoint, I can distinguish a very bad chess player from a good one without seeing a single game he/she has played. Just looking at his/her behavior and countenance in front of the board is enough. As an extreme example, you probably have seen a (very bad) player put his finger on the piece he wants to move, than keep it there and look around on the board, verifying that he will not immediately lose his piece when he complete his intended move. A better player will have made a final decision on his play before his arm starts to move. A much more subtle example: better players place their pieces more accurately in the center of their square, particularly in blitz games. Now I don't claim to distinguish a 2400 elo player from a 2500 elo. But a 1500 from a 1800 elo? Sure.