Octopuses have a REM-like sleep state where they appear to dream

Octopuses have two stages of sleep, including an active one in which they appear to dream, according to one of the most conclusive studies of their brainwaves and skin patterns yet.

When people sleep, we cycle through four stages. One of these is the rapid eye movement (REM) stage where brain activity increases and we dream, and the others where our brains are more quiet are called non-rapid eye movement (NREM). Birds and mammals like mice also cycle between a REM and a NREM stage, …