Do Dogs Dream? The Scientific Evidence Says "Yes"
Dogs spend the majority of their days sleeping. That’s according to the National Sleep Foundation, which reports that on average dogs spend between 12 and 14 hours sleeping every day. Puppies and older dogs are asleep even more than that, anywhere from 18 to 20 hours a day. The question which has perplexed dog owners since dogs were domesticated is, do they dream while they’re asleep, and, if they do, what exactly do they dream about?
What’s the Scientific Evidence?
Unfortunately, we can’t get inside your dog's head to know what happens while he's asleep, but there is some strong scientific evidence to support the notion that dogs dream. Much of that evidence comes from research conducted by Matt Wilson, a neuroscientist at MIT who focuses on memory and learning. Wilson points to the similarities between the brain structures of various mammals, including humans and dogs:
“When you look at brain structure, when you look at sleep physiology, the brain activity that goes on, the equivalence of the sleep states, it's all very comparable.”
Wilson points in addition to similarities in measurable sleep behaviors among many varieties of mammals, such as the rapid eye movement (REM) associated with dreaming in humans. In addition, both dogs and humans display increased levels of brain activity during sleep, and the brains of both humans and dogs have a brain structure—the Pons Varolii—which disallows movement during sleep, essentially causing muscle paralysis, a hereditary adaptation which protects the dreamer from accidentally hurting himself by acting out what he’s experiencing while dreaming.
Have There Been Any Scientific Studies Related to Mammalian Dreaming?
Wilson conducted a series of experiments the purpose of which was to better understand if the physiological similarities among more advanced mammals extended to similar experiences with dreaming. He measured changes in the activity of neurons in rats’ brains (specifically, in the hippocampus) as they ran through a maze, observing a distinct “firing pattern.”
He then measured hippocampus neuron activity while the rats slept and noted precisely the same changes. He concluded that the most logical explanation was that the rats were reliving their experience running through the maze—in dreams.
Several years later, Wilson performed essentially the same experiment, but this time focused on neurons in the rats’ visual cortex—the part of the brain that processes visual information—rather than those in the hippocampus. He once again observed virtually identical neuron firing during sleep and during the rats’ maze running.
He now felt confident not only that the rats were dreaming, but that in addition (and like human beings) the rats’ experience during sleep included a visual component—they were, in other words, seeing images in their dreams. For Wilson, the results of his experiments led to an inescapable conclusion:
“When the hippocampus replayed these little sequences, the visual cortex also replayed the corresponding visual perceptions. So the animal was quite literally seeing what it was replaying from memory. For me, that constitutes the necessary ingredients for referring to this as the equivalent of dreaming in animals. They're experiencing things and they're also perceiving what those experiences were.”
One of our patients dreaming away and snoozing comfortably after surgery
Has Anyone Conducted Similar Experiments with Dogs?
Although there has been no similar scientific experimentation involving dogs, scientists have studied sleep behavior in cats. For example, as reported in a study published in the Journal of Sleep Research, scientists found that when the Pons Varolii of cats was chemically disabled from functioning during sleep, they began moving—some walked in their sleep, while others began displaying classic predatory behavior, like tracking and pouncing on invisible objects. The researchers concluded that, because the brain structure which in normal functioning prevents movement during sleep had been effectively disabled, the cats’ movements could be attributed to mental triggers which were produced in dreams.
Wilson viewed this study as reinforcing his own findings regarding the pervasiveness of dreaming among higher mammals, including dogs:
“Increasingly, we're seeing that sleep and its functions, and very likely dreams, are something that are probably quite ubiquitous (across the animal kingdom).”
Do We Know What Dogs Dream About?
Although no one can state with scientific certainty what dogs or other mammals dream about, Wilson’s experiments with rats strongly suggest that animals dream about things which replicate their waking experience. Wilson feels this most likely means that dogs dream about the walk you took them on that day, or fetching the ball you threw, or running in the backyard
“The dream experiences can be traced back to real experiences. It’s memory that’s being used to synthesize the content of the dreams.”
Is It Dangerous to Wake Your Dog While He’s Dreaming?
It’s not unreasonable for you to conclude that, when your dog begins moving his legs, or growling, or twitching while he’s asleep, he’s probably dreaming. Although it’s not really dangerous to wake him up at these times, it’s not a good idea. Periods of rapid eye movement, and dreaming, occur during the deepest stages of sleep, and waking your dog would certainly be startling for him—as it would be for you.
According to Dr. Joan Hendricks, Dean of the School of Veterinary Medicine at the University of Pennsylvania, dogs move more vigorously than humans and other species during their sleep. This is normal and shouldn’t necessarily be interpreted as indicating a medical problem, such as a seizure or sleep disorder.
On the other hand, if you observe dramatic changes in your dog’s sleep patterns or behavior and are concerned that it might point to an underlying medical issue, your best bet is to have him checked out by your veterinarian. If you want more information or have any concern about your dog’s health, contact us today.
About Dr. Natalie Waggener
Dr. Natalie Waggener has 17 years of experience in emergency work and general practice in Rhode Island, Florida and Massachusetts. She has a special interest in dentistry, wellness care and rehabilitation therapy. She is currently licensed in both Massachusetts and Rhode Island.