A lot of things dogs do are really funny. But this can obscure that a fundamental truth is being revealed. So first enjoy a good laugh in the video below that's been making the rounds, and then try to answer: Why do dogs do this? It's no laughing matter. Below I will add my interpretation.
When you put a pair of batteries into a portable radio (remember those?), because the polarity markings inside the radio can be impossible to see, you learn to take note of the arrangement of the batteries as you take them out so that you will put the new ones in to their right slots. The (-) and (+) poles of the batteries must connect with the complementary (+) and (-) terminals inside the radio in order to complete the circuit so that energy will flow.
Likewise, an animal has a bi-polar emotional makeup. Stress is absorbed and stored in an emotional battery according to this bi-polar makeup. The head is the positive (+) pole and the butt is the negative (-) polarity. In the video you will note that the dogs aren't randomly sitting on the cats, they are specifically targeting the cats' head with their hind ends. This is because dogs become particularly sensitive of a cats head and claw action because cats aren't as good at Mawing as are dogs. They tend to go right to clasp and claw mode which is pretty overwhelming to a dog. So the dog in order to connect and simultaneously neutralize the cat's predatory aspect, sits on it which grounds out the balance problem of the cat's predatory aspect, neutralizing it by completing a circuit. In other words, two batteries are coupling according to the (+) ---> (-) (+)------> (-) i.e. grounding it out. This is closely related to humping between dogs who are better at Mawing and so there's a lot less sitting going on when the poles start flipping. You see more hubba-hubba when things bog down. Nevertheless all these kinds of affiliative behaviors can be labeled as "wave coupling." It's a systems logic that begins with the negative meeting positive, and positive meeting negative in order to complete the circuit, the dog being the most adaptive component of the module because the dog rather than the cat is doing the flipping of poles to conform to the energetic parameters that allow for emotion as energy to flow. This is a funny video but it nonetheless reveals the underlying architecture of the animal mind.