“Infants differentially responded to tongue protrusion with tongue protrusion and not lip protrusion, showing that a specific body part can be identified. Infants also differentially responded to lip protrusion versus lip opening, showing that differential action patterns can be imitated with the same body part. They even differentially imitated two separate kinds of acts with the tongue—one that is poking in-out from the midline, and the other that is poking in-out from the side of the mouth.”