Experimental setup and apparatus used by group one.

<p>The diagram of the box shows the cooperative apparatus. Stones dropped through the hole on the surface of the box would hit a baited central platform, causing the platform to swing downwards and release the food. The large diagram shows the setup of the box between two cages. The crow on the left (‘passer’/subject) had to pick up a stone and place it next to one of two gaps in the wire mesh divider (passing locations). The crow on the right (‘dropper’/partner) could then drop the stone into the apparatus and release food into both cages. For group two, the hole in the apparatus was on the left.