What do rooks (Corvus frugilegus) understand about physical contact?

Rooks (Corvus frugilegus) do not use tools, but rapidly solve tests of physical cognition. The authors tested whether rooks understand the concept of physical contact using a task comprising a clear horizontal tube containing a stick with a disk attached to it and a piece of food. The rooks chose which side to pull the stick from to make the food accessible. Two configurations were used, with either the food or disk central along the tube. All 8 rooks solved the food-central configuration, but failed the disk-central configuration. Although they did not demonstrate an understanding of contact, further tests established that they could team to solve these tasks provided there were salient stick cues. This result may arise because sticks are ecologically important for rooks.