Watching the change ripple across the communal dancers, from front to back, in various degrees of sync to the music and instructor. Observing confidence, measured by number of frantic glances at neighbors and proximity to instructor (closeness to instructor and this measure of confidence varying roughly directly – seemingly a human fault that the less certain tend to stay back where less can see them make the errors they fear making, whilst they sacrifice the opportunity to more easily and effectively observe the instructor).