Do octopuses dream?

Octopuses sleep. When they do, they usually go pale and still. But every so often, something remarkable happens.

Two kinds of sleep

Researchers have found that octopus sleep has two stages. Quiet sleep is interrupted by short bursts of what scientists call active sleep. During these bursts, which last about a minute, the octopus's body twitches and its skin rapidly flickers through colors and patterns. Source Medeiros et al., 2021(opens in a new tab)Source Pophale et al., 2023(opens in a new tab)

Patterns from the waking world

A 2023 study in Nature looked closely at those patterns. The skin displays during active sleep strongly resembled the ones octopuses show while awake. Recordings from the brain told a similar story. Brain activity during active sleep looked like waking activity, and it was strongest in regions associated with learning and memory. Source Pophale et al., 2023(opens in a new tab)

Active sleep also behaves like real sleep. It's harder to wake an octopus during these bursts, and when researchers interrupted their sleep, the octopuses made up for it later. Source Pophale et al., 2023(opens in a new tab)

So, are they dreaming?

Scientists have compared active sleep to REM sleep, the stage when people have most of their vivid dreams. Source Pophale et al., 2023(opens in a new tab)

What an octopus experiences during active sleep, if anything, is something no one can know for sure. But it's a striking parallel between our minds and theirs, given that our lineages split more than 500 million years ago. Source Pophale et al., 2023(opens in a new tab)

Bucky's take? He dreamt about a really good rock.