We've all noticed our canine friends fast asleep and appearing to dream; whether their legs move or they whimper and talk in their sleep, it seems pretty clear to the casual observer that there's little puppy dreams going on as they snooze.
But do they really dream?
Science says that they do.
Several universities -- including MIT -- have conducted experiments that monitor the brain activity of sleeping dogs in much the same way they study the activity of the minds of sleeping people. What they've found is that dogs have a sleep cycle very similar to that of humans; while they start out in a state with slow wave sleep patterns, a dog that continues to sleep will pass into a state of REM sleep. Also as with humans, this is were most dreams seem to occur.
Interestingly, the duration of these period of deep sleep seem to vary with breed, with larger dogs going through much longer periods of REM sleep.
When dogs are in the various stages of sleep, the electrical activity in their brains looks very similar to the patterns exhibited by sleeping -- and dreaming -- people. Even the part of the brain responsible for dreaming in humans, the hippocampus, is not only present in dogs but is biologically very similar. This structure isn't just common to humans and dogs, either -- it's in almost every animal on earth. Even rats have demonstrated the same dreaming behavior we see in our dogs.
So what do dogs dream about? Science thinks it's also figured that one out, too. Much like humans, it's thought that dogs often dream about everyday activities. Numerous instances of dogs waking from a sound sleep and reacting in a very particular way to outside stimulus that just isn't there reinforces this theory. For example, if your dog runs to grab his leash when you get your car keys, a dog bolting up from a sound sleep and running for his leash suggests that he's just been dreaming about the moment before going walkies. This is also why a large percentage of dog bites occur when someone wakes a sleeping dog; chances are, their brains haven't completely shut off their dreams yet, and they're reacting to something that could be the human equivalent of the zombie apocalypse.
It's also thought that dreams are breed and dog specific. Some dogs will show more running or digging activities, while other dogs might be more vocal. And scientists have found a correlation between daytime activities and nighttime dreams. The age of the dog also seems to dictate how long a dog's REM sleep stage is, and how vivid their dreams. Puppies have been shown to spend the most amount of time in REM sleep; while part of the reason is undoubtedly physiological, it has also been suggested that dreams help puppies to process the overload of new information they are exposed to during their waking hours.
So science has indicated the truth behind what dog owners have known for years. But is there a larger impact of this discovery?
For many, animals are simply animals. They are thought to function on instinct alone, simply reacting to outside stimuli without thinking or reasoning. The knowledge that dogs are dreaming means that they are thinking about what's going on around them, remembering what happened to them during the day, and processing all the information they receive in a way that is more similar to humans than previously thought.
This goes a long way in painting an entirely different picture of animals to people who previously believed them creatures only capable of living in the moment and reacting to their immediate surroundings.