Octopuses may experience dreaming similarly to humans, study finds

Cephalopods are thought to undergo two different stages of sleep: ”quiet” and “active” – the latter includes body parts twitching and changes in the pattern and texture of the skin.

According to researchers at the Okinawa Institute of Science and Technology (OIST) in Japan, scientists have not only determined that octopuses are in fact asleep during this “active” stage, but close similarities with REM sleep – seen in vertebrates including humans – were also observed.

REM sleep is a phase of slumber closely associated with dreaming. 

The team’s lead author, Professor Sam Reiter, said that results were “consistent” with the idea that octopuses dream.

“We can associate certain skin patterns during wakefulness to certain situations: hunting, social displays, threat displays, camouflage to different sorts of environments. We show that these patterns reappear during active sleep,” Reiter said, per The Guardian.

“So, if we are looking at something like dream, and I repeat this is a possibility we do not prove in this study, they would resemble a pseudo random walk over different types of waking experiences.”

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Another possible reason for the changing of texture in the animals’ skin during could be due to a “refining of pattern”, Reiter added.

The study found that of the 29 octopuses studied, the animals tended to close their eyes in daylight and “adopted a resting posture associated with sleep”.

Every 60 minutes or so during this period, they would undergo “rapid changes of skin colour” lasting a minute, with changes in breathing rate, as well as body and eye movements observed.

When scientists tapped on the tanks and watched how the octopus responded, they found the animals showed a range different reactions, depending on whether they were awake, in the quiet stage of sleep, or in the active stage.