The Spring 2009 issue of Notre Dame Magazine has a fascinating story on the mental capacity of dogs. In “The Natural Goodness of Dogs,” writer Jake Page relates, among other things, that:

In a recent series of experiments at the University of Vienna, Friederike Range rewarded dogs with a food treat if they held up a paw. Then when a lone dog was asked to hold up its paw, did so, and didn’t get a treat, it would keep on trying as many as 30 times. But when two dogs together were tested, with one of them not receiving a reward, the dog who was unrewarded made a big scene and soon refused to play. “Dogs,” said Range, “show a strong aversion to inequity.”