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Yog-Yogguth writes:

Ravens are known to be smart and IFLScience has a good summary [iflscience.com] of a new study which shows ravens recognize cheaters and won't trust them to the extent of refusing to cooperate with them if they have been cheated badly enough, and also that the cheaters were likely to try to cheat again if given another chance.

Nine young ravens, six of them male and three female, were gradually familiarized with the experimental setup before first being put through 600 trials where they got to freely choose who to cooperate with. Later through a few hundred more trials in total each raven was tested on the same task with each other raven in turn (i.e. no free selection of cooperation partner) as well as on their own to see if they would try the same experiment even when cooperation and success was impossible. They also tried to test for the importance of a raven observing the cooperating partner during the trial with much poorer results showing that while the ravens often cooperated successfully in the previous trials most of them hadn't really understood the details of how the cooperation —or the experiement or both— worked.

The ravens were shown to be the most successful when they were in pairs of one male and one female and also when there was a larger difference in the hierarchy of dominance between the cooperating ravens. The success rate for self-selected pairs was 66.2% while the success rate for assigned partners was only 27.3%. 84.38% of the ravens pulled the string in the control trials without a partner where it could not result in a reward (then again it seems there was nothing lost by trying and no reason why they shouldn't try even on the slimmest chance it might work even if they realized it shouldn't).

Link to the full paper "Tolerance and reward equity predict cooperation in ravens" [nature.com] in Nature, also available as a PDF [nature.com] (635 KB). It's eleven pages long and filled to the brim with information.

The most surprising to me is that ravens apparently love cheese :)

Hat tip to Schneier's blog which mentioned [schneier.com] the story.

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