Monster of the Week: The Nightmare

The Nightmare I, 1781. by Füssli Fine Art Images/Heritage/Getty

This week's monster takes a variety of forms, but its modus operandi is always the same. It attacks during the night, a dark and oppressive form that slithers on top of us in bed, crushing our bodies and stealing our precious breath.

The most common English name is of course "nightmare," stemming from the Anglo-Saxon "mara," which translates to "crusher." The fiendish mara looks like a small elf or imp, much like the chest squatter from Henry Fuseli's famed painting. Other species of nightmare, however, take on wilder forms...

Mahr: According to folk historian Carol Rose, this German subspecies may appear as a long hair, a wisp of straw or an "ugly little shape that vanishes when observed."

Cauchermar: This French nightmare species poses the typical threats to a good night's sleep, but also features a few weakness for you to exploit. Try placing iron nails under your mattress, pointing your toes outward at the bedside or sleeping with your head pointed North.

Ephialtes: Translated as "leaper," this Greek nightmare species also traps a troubled sleeper under its bulk, but mounts its prey with a frog-like leap.

The Old Hag: This variant haunts Newfoundland (where I spent part of my childhood) and appears as an old crone.

And of course cats (particularly those serving as a witch's familiar) catch a bad rap for this purported behavior as well. Don't believe it.

The Science of the Maras

What's it all about? Well, as Oliver Sacks points out in "Hallucinations," so many of these nightmare myths (as well as modern alien abduction experiences) boil down to sleep paralysis. See, during REM sleep our skeletal muscles are on lock down to keep us from thrashing around too much during dreams. It's just a simulation, see? No reason to ACTUALLY throw karate chops. But sometimes this safety feature malfunctions: The brain wakes up, but the body is still paralyzed in this "safe mode."

If the stats hold true, 20 percent of you know this first hand and don't need a description. For the rest of you, understand that it's a very unsettling experience. You wake up in the dark and you can't move! You panic! It's as if some force is holding you down or perched upon your chest! Drag a little of your dream memories into the waking world with you (along with residual sexual arousal) and a magical explanation practically writes itself.

And speaking of sexual arousal, next time we'll chat about close relatives of the nightmare: incubi and succubi.

(Nightmare. Paul Bielaczyc. charcoal, 2005.)

Monster of the Week is a - you guessed it - regular look at the denizens is of our monster-haunted world. Sometimes we'll focus on the cultural aspects, but mostly we'll look at the possible science behind a creature of myth, movie or legend. Be sure to explore the Monster Gallery as well as the Monster Science video series.

About the Author: Robert Lamb spent his childhood reading books and staring into the woods — first in Newfoundland, Canada and then in rural Tennessee. There was also a long stretch in which he was terrified of alien abduction. He earned a degree in creative writing. He taught high school and then attended journalism school. He wrote for the smallest of small-town newspapers before finally becoming a full-time science writer and podcaster. He’s currently a senior writer at HowStuffWorks and has co-hosted the science podcast Stuff to Blow Your Mind since its inception in 2010. In his spare time, he enjoys traveling with his wife Bonnie, discussing dinosaurs with his son Bastian and crafting the occasional work of fiction.