Recent research suggests that our boxers (and all dogs) learn to associate words differently than we do.  Science Daily reports on a study that suggests that dogs associate objects by size or texture and NOT by shape:  The article concludes that…

Though your dog understands the command “Fetch the ball,” but he may think of the object in a very different way than you do when he hears it. As the authors explain, “Where shape matters for us, size or texture matters more for your dog. This study shows for the first time that there is a qualitative difference in word comprehension in the dog compared to word comprehension in humans.”

So the next time you teach your dog to associate a word with an object, consider the size a texture of the object.  You wouldn’t want your dog to think a ball is the same thing as an orange!