“Stop copying me!” shrieks a friend's seven-year-old as she admires her bead-bedecked image in the mirror. “I not copying!” responds her three-year-old sister indignantly, while fingering rows of beaded necklaces around her own neck. Anyone who has observed a similar scene knows that a heated argument follows about “what counts” as copying, and whether playing with beads might be the result of the beckoning sparkle of beads or the desire to do whatever an older sibling does. What counts as copying, and similarly what counts as imitation, depends not only on arbitrary boundaries drawn by scientists and three-year-olds, but on the motivations and mechanisms involved. At least four mechanisms have been proposed to explain behaviors performed after seeing them performed by another animal. The likelihood of some behaviors is increased by stimulus enhancement when an object is manipulated by an animal subsequent to being handled or moved by another animal (Thorpe, 1956). The object itself is considered to trigger the behavior, perhaps through perceptual affordances, and the behavior of the first animal merely highlights the object, rather than providing an action model. Alternatively, some behaviors may be initiated by the observation of an action model, which triggers a specific and preorganized action pattern. Such innate releasing mechanisms (Lorenz & Tinbergen, 1938, as cited in Meltzoff & Moore, 1983) may explain exact copying of surprisingly complex behaviors observed in many nonhuman animals.