@article {309935,
	title = {Elephants know when they need a helping trunk in a cooperative task},
	journal = {Proceedings of the National Academy of Sciences},
	volume = {108},
	year = {2011},
	pages = {5116-5121},
	abstract = {<p>Elephants are widely assumed to be among the most cognitively advanced animals, even though systematic evidence is lacking. This void in knowledge is mainly due to the danger and difficulty of submitting the largest land animal to behavioral experiments. In an attempt to change this situation, a classical 1930s cooperation paradigm commonly tested on monkeys and apes was modified by using a procedure originally designed for chimpanzees (Pan troglodytes) to measure the reactions of Asian elephants (Elephas maximus). This paradigm explores the cognition underlying coordination toward a shared goal. What do animals know or learn about the benefits of cooperation? Can they learn critical elements of a partner{\textquoteright}s role in cooperation? Whereas observations in nature suggest such understanding in nonhuman primates, experimental results have been mixed, and little evidence exists with regards to nonprimates. Here, we show that elephants can learn to coordinate with a partner in a task requiring two individuals to simultaneously pull two ends of the same rope to obtain a reward. Not only did the elephants act together, they inhibited the pulling response for up to 45 s if the arrival of a partner was delayed. They also grasped that there was no point to pulling if the partner lacked access to the rope. Such results have been interpreted as demonstrating an understanding of cooperation. Through convergent evolution, elephants may have reached a cooperative skill level on a par with that of chimpanzees.</p>
},
	doi = {10.1073/pnas.1101765108},
	url = {http://www.pnas.org/content/108/12/5116.abstract},
	author = {Plotnik, J. M. and Lair, R. and Suphachoksahakun, W. and de Waal, F. B. M.}
}
