I do it partly because I like to challenge him and keep his mind active, but I also think that dogs are capable of a lot more than most of us give them credit for, especially when it comes to communication. Have you ever heard of Koko the gorilla? Did you know that the Koko Gorilla Foundation uses or used "gorilla companion dogs " who use language boards to communicate? They know lots of words for different things, and are able to point to a board to communicate their desires. See this archived page for more details. There has also been at least one study where a dog was taught to use talking language boards. That's what inspired me to get talking buttons for Cooper. I don't think that a dog has to be extremely intelligent to learn to communicate using devices either. A lot of people say, "Oh Cooper, you're so smart" when they see him using his talking buttons or playing with a child's toy. Cooper isn't stupid, but I don't think he's a genius either. I believe that most dogs could learn to do the same things as him. Most people just don't think to teach their dogs that kind of thing, maybe because they don't think it's possible! I don't teach Cooper these things to brag that he's smart. I teach Cooper these things to prove that it's possible, and to invite others to challenge their dogs as well :-)
Also, something important to note: before I teach Cooper any of these advanced tricks, I try to check that the trick is something that a dog might be physically capable of doing. That normally means that I research to see if anyone has done any relevant studies where they tested to see if dogs are capable of doing certain tasks. So before I taught him to sort by color, I researched to see which colors dogs could see most clearly. Before I taught him to sort shapes, I researched to see if dogs could even recognize different shapes. I normally don't bother trying to teach him something advanced unless there is already some kind of research out there which shows it should or could be possible. Although these are "tricks," I also see them as mini experiments and I want the results to be REAL, not the result of luck or clever video editing. If you see Cooper performing a trick, that means I have seen or read something which made me think a dog should be able to do that trick. I want to test his limits, but I also don't want to waste my time trying to get him to do something impossible.