Robert Todd Carroll
sleep paralysis
Sleep paralysis is a condition which occurs in that state just before a person drops off to sleep (the hypnagogic state) or just before they fully awaken from sleep (the hypnopompic state). The condition is characterized by being unable to move or speak. It is often associated with a feeling that there is some sort of presence, a feeling which often arouses fear but is also accompanied by an inability to cry out. The paralysis may last only a few seconds. The description of the symptoms of sleep paralysis is similar to the description many alien abductees give in recounting their abduction experiences. Sleep paralysis is thought by some to account for not only many alien abduction delusions, but also other delusions involving paranormal or supernatural experiences.
Sleep paralysis is something many people experience once or twice in a lifetime but it is a frequent occurrence of those suffering from narcolepsy.
further reading
Robert Todd Carroll
philosophical skepticism