Why do you train Cooper with food instead of love?

Cooper is rewarded with a combination of food, love, and praise :) Cooper is very food-motivated so when he's first learning a trick he needs to be rewarded with food to keep his attention, but once he's learned a trick he is not always rewarded with food. However I do normally use food in videos to ensure that he's focused so I can get a good recording within a short timeframe.

For some tricks he actually does better when he can't see I have treats, because the treats excite him and make him lose focus. But for tricks that are complicated and require lots of mental effort, he still needs an occasional treat to stay motivated and interested, and I don't think there's anything wrong with that :)