A Glimpse Inside the Mindof Dreaming Animals
Avery Hurt 埃夫丽·赫特
f you've ever watched dogs or cats sleep， you've probably wondered if they're dreaming. Was that ear twitch or snuffling sound just a reflex？ Or is Fluffy dreaming of the hunt？ Maybe the sound of the can opener？ Since we can't ask， we may never know for sure. But there are good reasons to think non-human animals dream，at least according to a certain definition of dreaming.
Human dreaming occurs mostly， but not exclusively， in the state known as REM（rapid eye movement） sleep. During this phase， the electrical activity in the brain is more like waking than sleeping. Scientists have discovered that most non-human animals — mammals， birds， reptiles， and most recently， fish — experience REM sleep， too. The electrical activity in these creatures' brains during REM sleep is quite similar to that of humans while they dream.
A 2015 study on rats offered an even more intriguing peek into the minds of sleeping animals. Researchers at University College London monitored the brain activity of rats as they showed the rats the location of food and taught them the route through a maze to get there. They didn't allow the rats to actually reach the food， though. Later when the rats were sleeping， they monitored the rats' brain activity. Next， they put the rats back in the maze， without blocking them from the food. While the rats found their way to the food， their brain activity showed the same patterns they had while sleeping， indicating that while snoozing the rats rehearsed the route they had learned earlier.
This is consistent with what sleep is thought to do in humans. Philippe Mourrain， an associate professor of psychiatry and behavioral sciences at Stanford University，explains that during sleep the brain stabilizes and integrates what you've experienced the day before — a process often called memory consolidation.
Non-human animals need to consolidate what's happened to them during their waking hours， too. So， does this mean that as their brains try to organize new information， these animals have weird dreams about interesting smells， dangerous predators or the alluring sounds of food in the kitchen？ That's very likely.
It begs questions about whether animals wake up and remember these images， and maybe even， like humans， attach a storyline to them. They likely do not.
In the end， we may have the question turned around. “I think the message is not， ‘Animals are dreaming like us，’ ”says Mourrain， “but we're dreaming like them.”
But that doesn't mean the dreams of one species are anything like the dreams of another. To paraphrase the philosopher Ludwig Wittgenstein， “If a lion could tell us about his dreams， we would not understand him.” Marc Bekoff， an evolutionary biologist at the University of Colorado， Boulder， put it another way: “I think it depends on how you define ‘dream.’”