A game of tennis provides ample lessons in human nature. (For that matter, most games help us understand human nature.)
Kim and Charles Petty tell us “Tennis psychology is nothing more than understanding the workings of your opponent’s mind, and gauging the effect of your own game on his mental viewpoint, and understanding the mental effects resulting from the various external causes on your own mind”. (You can read the complete article here.)
Tennis is eminently suited for the study of human nature as it involves two individuals. Can you think of any other game that helps understand human nature better?