One raven in the experiment figured out how to work their rock/box contraption first, then began teaching the method to other ravens, and finally invented its own way of doing it. Instead of dropping a rock to release a treat, the future Ruler of the Raven Kingdom constructed a layer of twigs in the tube, and pushed another stick down through the layer to force it open. The bird had to be removed from the experiment before it could teach any other birds how to do it.

[link to motherboard.vice.com (secure)]

Ravens perform better in bartering tests than orangutans, bonobos, and chimps.

And

Ravens can “select, save, and later use either a tool or an exchangeable token that acquired functionality” both 15 minutes and 17 hours after being taken.

[link to science.sciencemag.org]