The scene: a dog and a human, seated at the table. In front of each is a cardboard box, the kind that fast-food hamburgers are packaged in. The boxes are identical. The human opens their box to reveal a nice-looking full-sized burger. Then tnhe human opens the dog's box to reveal a miniature and possibly fake burger. The dog looks at the little burger, bares its teeth, and growls.
It reminds me of the grape/cucumber experiment with monkeys. A monkey receives a piece of cucumber each time it completed a task. Then it was allowed to see another monkey get a grape as a reward for doing the same task. The cucumber monkey threw a fit because it wasn't getting the same reward as the grape monkey. It wanted the tastier grape. When the experiment tried giving the first monkey a cucumber again, it threw the cucumber at the experimenter. The lesson from the experiment is that even monkeys can get upset when they feel they are being treated unfairly.
Is the dog upset that it isn't getting the same kind of burger as the human? It may not be as sophistiIs the dog upset that it isn't getting the same kind of burger as the human? It may not be as sophisticated as the monkey in the experiment, but it seems to be able to tell that the two burgers are not the same. The scientist in the video below says dogs and even birds can sense unfairness, so it's possible that the dog in this video is feeling cheated.