Octopuses Appear to Dream. What Does That Tell Us About the Evolution of Sleep?

When an octopus sleeps, it changes colors. Maybe you’ve seen that in an aquarium or watching one of those viral videos. It’s cool. Researchers in Brazil recently discovered that octopuses cycle through passive and active sleep stages—like we do with have REM and non-REM sleep stages. And since REM sleep is when we do most of our dreaming, does that mean octopuses dream too? Sidarta Ribeiro, a neuroscientist at the Brain Institute at the Federal University of Rio Grande do Norte in Brazil, studies sleep, dreaming, and these octopuses.