BrainDance

← All posts · dream-science ·

Do Animals Dream? What Rats, Dogs, and Octopuses Show Us

Do animals dream? Research on rat memory replay, dog REM sleep behavior, and octopus color shifts suggests many animals may have dream-like brain states.

Most sleep researchers think the honest answer is: probably, in some form, but we can’t ask them and confirm it. Rats show hippocampal activity during sleep that mirrors their waking maze runs, dogs twitch and vocalize in patterns consistent with dream-like mental activity during REM sleep, and octopuses shift skin color and texture during an active sleep phase in ways that resemble their waking camouflage displays. None of this proves subjective experience, but together it points to dreaming — or something dream-adjacent — being older and more widespread than we once assumed.

Do animals dream?

We can’t know for certain, because dreaming as humans describe it is a subjective, first-person experience, and animals can’t report it to us. What researchers can measure is brain activity, eye movement, muscle tone, and behavior during sleep, and in several species those measurements look strikingly similar to what happens in a sleeping, dreaming human brain. This is why most scientists in the field speak carefully, using phrases like “consistent with dreaming” rather than claiming certainty. The evidence is indirect but consistent across species, which is itself notable.

Do dogs dream?

Dogs very likely have some form of dream-like brain activity during REM sleep, based on their brain wave patterns and the twitching, paddling, and soft vocalizing many owners notice. Dogs cycle through sleep stages similar to humans, including REM sleep marked by rapid eye movements and low muscle tone (McNamara & Barton, 2000s sleep-comparative research generally supports this). A 2017 EEG study of pet dogs found that their sleep architecture, including time spent in REM-like stages, was related to how well they had learned a new task earlier that day (Kis et al., 2017, https://doi.org/10.1038/srep41873). That’s not direct proof of dreaming, but it echoes findings in rats and humans where sleep seems tied to processing recent experience.

The twitching itself has an interesting backstory. In the 1960s, French researcher Michel Jouvet found that cats with a specific brainstem lesion lost the muscle paralysis that normally accompanies REM sleep, and instead of lying still, they got up and acted out apparent stalking, pouncing, and startled behaviors while still asleep. That muscle paralysis normally exists precisely to keep sleeping animals (including us) from acting out whatever the brain is generating during REM. In humans, a related condition is called REM sleep behavior disorder, and it’s a medical condition that should be evaluated by a sleep specialist rather than self-diagnosed from a pet’s or partner’s nighttime movements.

What do rat maze studies show about dream content?

Rat studies show that the same hippocampal brain cells active while a rat runs a maze fire again, in the same sequence, while the rat sleeps afterward. Wilson and McNaughton’s landmark 1994 study found this “replay” happening during sleep following a spatial task, suggesting the rat’s brain was reprocessing the maze experience (Wilson & McNaughton, 1994, https://doi.org/10.1126/science.8036517). A follow-up study went further, showing that during REM sleep specifically, the replay unfolded in real time and in the correct temporal order, closely matching the pace of the original waking run (Louie & Wilson, 2001, https://doi.org/10.1016/S0896-6273(01)00186-6). That real-time, sequential quality is part of why some researchers find it a reasonable proxy for something dream-like: it isn’t just noise, it’s structured, ordered, and tied to lived experience — which is also a decent working description of a lot of human dreams. This lines up with broader research on how sleep supports memory consolidation in general.

Why do octopuses change color while sleeping?

Octopuses shift skin color, texture, and even move their arms during an active phase of sleep, and some researchers think this may reflect the brain replaying or rehearsing camouflage patterns used while awake. A 2021 study on octopuses documented two distinct sleep states: a quiet phase and a shorter, more active phase during which skin patterns changed rapidly, resembling the dynamic camouflage octopuses use to hide from predators or ambush prey (Medeiros et al., 2021, https://doi.org/10.1016/j.isci.2021.102223). The researchers were careful to frame this as consistent with a dream-like state rather than proof of one, since an octopus’s nervous system is so different from a mammal’s that we should be cautious about assuming its inner experience, if any, resembles ours. Still, the fact that a creature this evolutionarily distant from us shows an active sleep phase at all suggests that alternating quiet and active sleep states may be a very old, widely conserved feature of animal brains, not something invented once in mammals.

What might dreaming be for, if animals do it too?

If many animals show dream-like brain activity, that’s often read as support for the idea that dreaming serves a function tied to survival, not just idle mental noise. A few leading theories, discussed in more depth in our overview of why we dream, include:

None of these are settled facts, and it’s entirely possible dreaming (in whichever species has it) does several of these jobs at once, or that its function differs meaningfully between species. The presence of REM-like sleep in rats, dogs, and octopuses doesn’t mean their sleeping minds work the same way ours do; it means whatever this sleep state is doing, it may have been useful enough, evolutionarily, to show up again and again in very different kinds of brains.

Should this change how you think about your own dreams?

Not dramatically, but it can be a useful reframe. If a rat’s brain is quietly rehearsing a maze run and an octopus’s skin is possibly echoing its camouflage routines, it becomes easier to see human dreaming as a biological process doing ordinary maintenance work — sorting memories, testing emotional responses, replaying the day — rather than something mysterious happening only to us. That doesn’t make dreams meaningless; it just grounds them in something more like digestion or muscle repair, a background process with real content worth paying attention to. Writing dreams down in a dream journal is one low-effort way to notice patterns over time, and if you’re curious what a particular dream might be pointing to, a free dream interpretation tool can offer one reading to consider alongside your own. For readers interested in the difference between REM and non-REM dream content, that split is explored further in REM vs NREM Dreams: Two Different Machines.

If disrupted sleep, unusual nighttime movements, or distressing dream content is affecting you or a pet’s wellbeing, it’s worth speaking with a doctor, veterinarian, or accredited sleep specialist rather than relying on general articles like this one.

Frequently asked questions

Can animals have nightmares?

We don't know for certain, since nightmares involve subjective fear that animals can't report, but distressed vocalizing or sudden waking during REM sleep in dogs and other animals is sometimes interpreted this way. It's a plausible extension of the same dream-like brain activity researchers observe, though it remains an interpretation rather than a confirmed fact.

Which animals have been shown to have REM sleep?

REM or REM-like sleep has been documented in most mammals studied, including rats, cats, and dogs, as well as in some birds and, more surprisingly, in cuttlefish and octopuses, which show an active sleep phase with rapid physiological changes. The presence of REM-like states across such different nervous systems is one reason researchers think dream-like activity may be evolutionarily old.

Do fish or insects dream?

There's little solid evidence either way, since most dream research has focused on mammals and a handful of cephalopods. Simpler nervous systems in many fish and insects may not support the kind of structured replay seen in rat hippocampal studies, but this remains an open and actively studied question.

Why do dogs twitch and make noise while sleeping?

Twitching, paddling, and soft vocalizing during a dog's sleep typically occur during REM-like stages, when brain activity increases but muscle tone is usually reduced. Occasional twitching is considered a normal part of dog sleep, though a veterinarian should be consulted if movements seem violent, prolonged, or paired with signs of distress.

Is animal dreaming the same as human dreaming?

Almost certainly not identical, since human dreams involve complex narrative, language, and self-reflection tied to our particular brain structure. What research shows is dream-like brain activity in other species — patterned, experience-linked, and tied to memory or behavior — which may share some functions with human dreaming without being the same experience.

Sources