When we go to sleep, we sometimes have dreams about a wide variety of subjects. Remarkably similarly, dogs are also capable of having dreams, sometimes about the same things. Anatomically, the structure of the canine brain is incredibly similar to the brain structure of humans. When they sleep, the same kinds of electrical activity surge through their brains, suggesting that they dream as well. Similar, rats have been capable of dreaming as well, so I guess it’s no surprise that dogs are capable of having dreams, too.
As for what the subject of dog dreams can be, it is widely assumed that they dream about common dog activities. They observed that rats sent similar electrical signals through their brains in the day as well as at night, so scientists assume the same is true for dogs. But the average pet owner does not need to read electrical brain signals of dogs to figure out if they dream or not.
About 20 minutes following the time a dog of average size dozes off and their breathing becomes regular, the first dog dreams begin. The dog’s breathing will become both irregular and shorter. The dog’s eyes may even be moving and their muscles will twitch oddly. The dogs view images in their dreams as if they are in fact real, which cause the eye motions while they dream. As such, they act out their dreams in sometimes very humorous ways. I’ve seen my dog running on the couch while dreaming, and it always cracks me up.