http://www.wired.com/techbiz/people/magazine/15-09/st_thompson

"Claudia Rutte and Michael Taborsky of the University of Berne, Switzerland, trained rats to pull a lever that released food for their partner in the next cage. If the rats subsequently received snacks released by lever-pulling strangers in neighbouring cages, they were more likely to lever-pull and so feed another unfamiliar rat in the future."Read more... )