Have you had the experience of "dancing in your seat" when you watch a performance of a piece you've rehearsed intensively? To the casual observer, it may look like you're just rhythmically working kinks out of your wrists or ankles and bobbing your head, but fellow dancers would probably recognize the self-contained choreographic reenactments. We can't help it!
This phenomenon is based on some really interesting activity that happens in your brain when you learn choreography. Dr. Steven Brown, a neuroscientist who studies differences between dancers' and non-dancers' brains at McMaster University, writes,
"Watching a motor act that is perceived as familiar and executable [i.e. a well-rehearsed variation] stimulates not only visual parts of the brain but motor-planning areas as well...The neural circuits involved in imitation are well-engaged during dance learning, thereby leading to the condition in trained dancers in which observation alone can stimulate the motor system."
This leads to particularly useful take-aways for learning strategies! Obviously, physical practice is critical for mastering any choreography, but you can supplement your studio time -- and constructively give your body some rest -- by watching videos of yourself or a favorite professional rehearsing or performing your piece. The exercise reinforces your memory of the choreography while giving you a chance to mentally play with and develop the details that make a performance special-like musicality, accents, épaulement, emotional connections, etc. Also, by mentally rehearsing a piece exactly as you hope to execute it, you can work out a lot of frustrating stumbling blocks without your body accidentally habituating any repeated mistakes.