Two more animals have been added to the annals of animal cooperation: elephants and African grey parrots.
The classical cooperation study used in chimpanzees and young children requires two individuals to perform a task. The two animals each must pull on a rope to bring a cart laden with treats within reach. If only one animal pulls, it will simply draw the rope completely out from around the cart.
The elephant study was conducted by Frans de Waal and his colleagues from Emory University and from the Forest Industry Organization in Lampang, Thailand. You can see some experiments below. Elephants were able to understand that that they must wait for a partner before pulling on their own rope.
The parrot study, led by Dalila Bovet of Paris West University Nanterre La Défense, showed similar results. However, African grey parrots were also able to divvy up two different types of tasks in order to get a reward. For example, one parrot might have to release a tray that the second parrot could then pull closer.