Very interesting. And yes, one implication occurred to me immediately. We play fetch with Jack daily, using a ball or kong-type throw toy. These sessions are fairly informal, but we always worry about their interfering with the more formal retrieve of a dumbbell and have been relying on the idea that context will help him distinguish between the two different protocols for fetching. This research seems to suggest that intuiting the difference between the ball and the dumbbell can contribute to his ability to make the distinction. This certainly was the case with our previous guy.