Dogs and fair play

Dogs refuse to play ball if they are treated unfairly according to this Guardian article which is a report on the findings of an article in the Proceedings of the National Academy of Sciences. As the article points out the dogs' behaviour could be the result of envy rather than a sense of fair play. Other recent research has pointed out that dogs are highly sensitive to human behavioural signals and so a sense of fair play could have developed from living amongst primates.