Lending A Helping Trunk

Natural selection generally promotes the success of individuals who look out for themselves – that is, selfishly.  But, there are also lots of examples of cooperative behavior in nature: for instance, the care of offspring, hunting, and sometimes, even problem solving.  This is because cooperation can be beneficial as well – being able to raise young successfully and leave more descendants, or simply enhance one’s own survival by working together to obtain food or other resources.

The experimental set up, from Plotnik et al. 2011

Cooperative problem solving has been of interest to those studying animal minds.  Different species demonstrate different degrees of awareness about what it takes to solve a particular challenge.  Joshua Plotnik, together with colleagues from Thailand, modified a very commonly-used experimental paradigm to test whether Asian elephants were capable of understanding cooperative problem solving [1].  They set up a series of very simple but elegant experiments.  12 elephants were split into pairs that had to jointly pull on a rope in order to gain access to a table containing food.  If either member of a team pulled on the rope by itself, the rope would slip out of reach for the partner, and neither of them would get the reward.  The elephants were first trained to pull on ropes to get food, then they were tested under three different conditions.

First, two elephants were released simultaneously.  They quickly mastered this condition, jointly tugging on the rope and getting their rewards.  However, one could argue that they weren’t really cooperating – they might simply have learned to pull on a rope whenever they saw one, associating that behavior with a reward.  To rule out this possibility, they had a second condition in which the animals were let out only one at a time.  The first animal would have to wait for the second – only patience would pay off.  The elephants also managed to do this quite successfully.  “But wait!” you say – “ok, what if the elephant had simply learned to pull on a rope whenever there was another elephant?”  Perhaps they don’t know they really need help from the other elephant at all.  To exclude this, they again released each pair at simultaneously, but this time only one of them would have access to the rope.  If elephants really understood teamwork, they would not pull whenever their partner didn’t also have the opportunity to do so.  The elephants realized this quickly – in fact, after a few initial attempts, they didn’t bother to pull the rope at all unless both of them could do it.  What’s more, different individuals approached the various conditions with slightly different strategies.  One even discovered that it worked just as well if all she did was step on the rope to prevent it from moving, while her partner did all the work of pulling, which is cheating a bit!

Elephants are not the only animals to complete this task successfully.  Chimpanzees and rooks, a species of corvid (relatives of crows), have also demonstrated cooperation on nearly identical tasks.  Rooks, for reasons as yet unknown, so far have not been able succeed under the delayed release condition – that is, they did not succeed unless both partners were let out at the same time because otherwise whoever got there first started pulling before the other arrived [2].  Chimpanzees on the other hand gradually learned by trial and error that they would be better off to wait; they could even transfer the skill to cooperate with humans and attempted to communicate what was required of their partners [3].

ResearchBlogging.org[1] Joshua M. Plotnik, Richard Lair, Wirot Suphachoksahakun, and Frans B. M. de Waal (2011). Elephants know when they need a helping trunk in a cooperative task Proceedings Of The National Academy of Sciences : 10.1073/pnas.1101765108

[2] Seed, A., Clayton, N., & Emery, N. (2008). Cooperative problem solving in rooks (Corvus frugilegus) Proceedings of the Royal Society B: Biological Sciences, 275 (1641), 1421-1429 DOI: 10.1098/rspb.2008.0111

[3] Hirata, S., & Fuwa, K. (2006). Chimpanzees (Pan troglodytes) learn to act with other individuals in a cooperative task Primates, 48 (1), 13-21 DOI: 10.1007/s10329-006-0022-1

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