““Imitation is a real instinct, but it is not always playful; play is a real instinct, but it is not always imitative. There is likely, however, to be a great deal of imitation in play, since the occasion on which a particular play-function develops is often that which also develops the imitative tendency as well — i. e., the actual sight or hearing of the acts or voices of other animals. Moreover, the acquisition of a muscular or vocal action through imitation makes it possible to repeat the same action afterwards in play.””
