Octopuses Dream in Color? Scientists Reveal Why Their Skin Changes During Sleep

Imagine watching an octopus resting at the bottom of a tank. Its body turns pale. It looks calm, almost faded into the background. Then, without warning, waves of color rush across its skin — dark spots appear, stripes ripple outward, textures shift. Its arms twitch. Its eyes move beneath closed lids.

No predator is nearby. No prey is passing by.

It’s asleep.


Recent laboratory research reveals that octopuses cycle through structured sleep stages, mirroring human and mammalian sleep patterns. Their dramatic color changes appear directly linked to brain activity, prompting researchers to investigate how these behaviors compare with human experiences of sleep.

Two Sleep States, Just Like Ours

A detailed study published in iScience documented that octopuses alternate between two distinct sleep states: quiet sleep and active sleep.

During quiet sleep, the octopus lies still. Its skin becomes smooth and pale. Breathing slows. There is little to no movement. This phase resembles deep, non-REM sleep in people.

After several minutes, the animal shifts into active sleep. This is when things get interesting. Its skin rapidly cycles through bold color displays. Dark and light patterns pulse across its body. The eyes move. The arms sometimes twitch or curl.

These active phases are short, often lasting less than a minute, and they repeat in regular cycles roughly every 30 to 40 minutes. The rhythm strongly mirrors the alternating non-REM and REM sleep stages observed in humans.

For an animal on a different evolutionary path, that similarity is striking.

Skin That Reflects the Brain

Octopus skin is unlike anything humans have. It contains millions of pigment cells called chromatophores. These cells are controlled directly by the nervous system, allowing the animal to change color and pattern almost instantly while awake — for camouflage, communication, or warning displays.

What makes sleep so fascinating is that these same chromatophores activate during active sleep, even though the octopus is not responding to the outside world.

Professor Sam Reiter and colleagues at the Okinawa Institute of Science and Technology studied these sleep cycles closely. They observed that the patterns displayed during active sleep often resemble patterns the octopus uses when awake, such as camouflage designs or bold contrast signals.

In a sense, the octopus’s skin may act like a screen, revealing internal brain activity.

Researchers propose that these organized sleep cycles reflect internal brain processes, possibly including memory replay or neural maintenance—paralleling how REM sleep supports such functions in humans.

The key point is that the patterns are organized. They are not random flickers. They appear structured and coordinated.

Are Octopuses Really Dreaming?

The word “dream” naturally comes to mind. But scientists remain cautious.

In the iScience research, investigators tested whether the animals were truly asleep by measuring how they responded to visual and touch stimuli. Both quiet and active states met scientific criteria for genuine sleep, not simple inactivity.

However, dreaming in humans involves subjective experience — images, emotions, narratives. An octopus cannot describe what it experiences. There is no way to ask what it “saw.”

Tamar Gutnick, an octopus researcher familiar with the work, has noted that the appearance of coherent waking-like patterns during sleep makes the idea of replay compelling. Still, evidence supports REM-like sleep behavior — not proof of human-style dreaming.

The distinction matters. The research shows structured, brain-driven sleep states but does not confirm conscious dream imagery.

Why This Changes How We See Sleep

Octopuses already surprise scientists with their intelligence. They solve puzzles, open containers, and adapt quickly to new environments. They have the most complex nervous system of any invertebrate.

The discovery of organized sleep stages in octopuses challenges traditional ideas about sleep evolution, emphasizing that complex sleep may not be unique to vertebrates.

In mammals, REM sleep is associated with learning, memory processing, and neural maintenance. Discovering similar sleep architecture in octopuses suggests that complex sleep may not belong only to animals with backbones. It may be a broader biological solution for supporting advanced brains.

What makes this even more remarkable is the evolutionary distance. Humans and octopuses share a very ancient common ancestor, yet both developed alternating sleep cycles that include an active, brain-engaged phase.

A Glimpse Into Another Mind

Watching an octopus drift into active sleep feels almost like witnessing a private moment. Color spreads across its body in patterns that once signaled hunting, hiding, or defense.

But now, there is no audience.

Whether or not it is dreaming, one thing is clear: its brain remains deeply active during rest. Beneath still water, a silent performance unfolds — not for survival, not for display, but as part of a hidden internal process.

For scientists, these orchestrated color changes are more than just a spectacle; they offer a rare window into the workings of a mind that, while different, demonstrates strikingly familiar elements of structured, active sleep.