Edge: "THAT DAMN BIRD": "We are going to do some more studies with recursion. Hauser, Chomsky and Fitch published a paper in Science at the end of October 2002 stating that only humans produce recursive phrases and that recursion is thus what separates human language from animal communication systems. Well, parrots, dolphins and sea lions respond to recursive sentences. Dolphins and sea lions will differentially respond to statements such as 'Touch the surfboard that is grey and to the left' versus 'Swim over the Frisbee that is black and to your right.' Alex responds to questions such as 'What object is green and three-corner?' versus 'What color is wood and four-corner?' or 'What shape is paper and purple?' "