As a college student in 1964, David J. Hufford met the dreaded Night Crusher. Exhausted from a bout of mononucleosis and studying for finals, Hufford retreated one December day to his rented, off-campus room and fell into a deep sleep. An hour later, he awoke with a start to the sound of the bedroom door creaking open–the same door he had locked and bolted before going to bed. Hufford then heard footsteps moving toward his bed and felt an evil presence. Terror gripped the young man, who couldn't move a muscle, his eyes plastered open in fright.

So starts the Science News article, "Night of the Crusher: The waking nightmare of sleep paralysis propels people into a spirit world" by Bruce Bower. The article looks at the typically frightening and not so uncommon experience of sleep paralysis, a nighttime "brain glitch," distict from nightmares and night terrors, which "embodies a universal, biologically based explanation for pervasive beliefs in spirits and supernatural beings."

Updated on 28 Feb 09: In the Dead of the Night at The Guardian is another article on this topic.