Cats are really, really good at sleeping. They sleep more than most mammals and twice as much as humans, typically sleeping about 15 hours every day.

With all that shuteye probably comes a good deal of dreaming. It's a little easier to study human dreaming: If you want to know what people dream about, you ask them. But because you can't ask animals and expect to get a response, the science is a little iffier.

Here's what we know — and what we think we know — about cats, sleep and dreams.

Aggressively on the hunt

Like us, cats have rapid eye movement (REM) sleep, which is when most dreaming occurs. During REM sleep, heart rate and breathing gets faster and eyes move about quickly in different directions.

In the 1960s, sleep researcher Michel Jouvet studied the biology of REM sleep in cats through experiments that made the cats' REM activity more visible. When REM began, instead of just lying there, the cats acted aggressively — arching their backs, pouncing and hissing as they stalked around the room. They acted as if they were looking for prey.

Veterinary neurologist Adrian Morrison, who has written a review of this research, says cats in REM sleep also will move their heads as if they are following or watching something. The research suggests that cats dream of being on the hunt, rather than merely lazily watching the world go by.

Dreaming about you?

cat sleeping with woman Your cat may be dreaming of you when she sleeps. (Photo: waniuszka/Shutterstock)

When they close their eyes, it's likely that cats have dreams that are a lot like ours, Matthew Wilson, an associate professor of brain and cognitive sciences at MIT’s Picower Institute for Learning and Memory tells Petful. We dream about our everyday lives and they dream about theirs. We just have different life experiences.

"Humans dream about the same things they’re interested in by day, though more visually and less logically. There's no reason to think animals are any different," Dr. Deirdre Barrett, who is a teacher and a clinical and evolutionary psychologist at Harvard Medical School, tells People.

If you have a dog, you may have warm, fuzzy dreams about walking or playing fetch with your pet, and those dreams may be reciprocated.

"Since dogs are generally extremely attached to their human owners, it's likely your dog is dreaming of your face, your smell and of pleasing or annoying you," Barrett says.

Cats likely dream of their humans too, but possibly they fantasize more about annoying them (or getting more food from them) than pleasing them.

Simultaneously asleep and awake

cat with one eye open Cats spend much of their time in a world where they are half awake, half asleep. (Photo: Top Photo Engineer/Shutterstock)

If it seems like your cat is always a second away from a catnap, that's because she is.

"Cats seem never to venture very far from sleep. Though they might be fully roused one moment, engaging in passionate play or serious stalking, cats seem able to slide effortlessly back into rest and sleep the next," says Rubin Naiman, Ph.D., a clinical psychologist specializing in integrative sleep and dream medicine at the University of Arizona's Center for Integrative Medicine.

Cats are crepuscular, Naiman says, meaning they are most active and awake during twilight at dusk and dawn. The rest of the day and night, they are in a hazy land of sleep-wake.

"Cats reside in the boundary between night and day — between waking and sleep. In fact, cats challenge the commonly held notion that it's impossible to be simultaneously asleep and awake," Naiman says. "Not only are they able to sleep while sitting up, their sense of smell and hearing can remain active during most of their sleep."

So your cat may be dreaming while sitting up, half awake. That's talent.

Do cats have nightmares?

You may see your cat sleeping peacefully and then he suddenly twitches uncontrollably with paws zipping about in what looks like general discomfort. There's a chance he's having a nightmare, or just reliving a negative event from the day. There's also a good chance it's just the typical muscle twitching that goes along with REM.

Even if you feel like your cat is having a bad dream, it's probably not a great idea to wake him up. He may be so startled that he could wake up with claws and teeth flying.

It's better to let a sleeping cat lie.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

What do cats dream about?
Cats spend so much time asleep that they have naps named for them. Here's how they dream.