One of the Cognitive ghosts discussed in the The Rest Is Science episode “Cognitive Ghosts”.
What it is
Sleep paralysis is waking up (or starting to fall asleep) with your mind alert but your body still paralysed — unable to move or speak for seconds to minutes. It’s often frightening, and frequently accompanied by a sense of a presence in the room, pressure on the chest, or shadowy hallucinations. It’s the mirror image of the Hypnic jerk: there, the body jolts while the mind sleeps; here, the mind wakes while the body stays switched off.
What’s happening in the brain
During REM sleep the brain deliberately paralyses the skeletal muscles (REM atonia) so you don’t physically act out your dreams. In sleep paralysis, consciousness comes back online before that atonia switches off — so you’re awake inside a still-sleeping body. The hallucinated intruder is the dreaming brain bleeding into waking perception; combined with the inability to move, it produces a primal terror. Folklore around the world (“the old hag”, the Mare, alien abductions) is widely thought to originate in sleep-paralysis episodes.
References from the show
- Presented as the opposite of the Hypnic jerk — body paralysed, mind awake — and as a contributor to night terrors and phantom sensations, including the feeling that someone else is present (a thread that connects to The Third Man Factor).
Links
Related
- Hypnic jerk — the inverse glitch at sleep onset
- The Third Man Factor — felt presence of someone unseen
- Cognitive ghosts