Dog deduction abilities

In an experiment by Friederike Range of the University of Vienna reported in the Washington Post, a border collie named Guinness would demonstrate to other dogs how to use her paw to push down on a bar to get a treat. Guinness would demonstrate in one of two different conditions--with a ball in her mouth, and without a ball in her mouth. Dogs prefer to use their mouths to move the bar, and so dogs that saw the demonstration while Guinness had a ball in her mouth inferred that she was only using her paw because her mouth was otherwise occupied, and would use their mouths. Dogs that saw her perform the demonstration without a ball would duplicate her demonstration, using their paws to push on the bar.