Dogs are becoming more intelligent and are even learning morals from human contact, scientists claim.
They say the fact that dogs’ play rarely escalates into a fight shows the animals abide by social rules.
During one study, dogs which held up a paw were rewarded with a food treat.
When a lone dog was asked to raise its paw but received no treat, the researchers found it begged for up to 30 minutes.
But when they tested two dogs together but rewarded only one, the dog which missed out soon stopped playing the game.
Dr Friederike Range, of the University of Vienna, who led the study, said: ‘Dogs show a strong aversion to inequity. I would prefer not to call it a sense of fairness, but others might.’