by Robert Novella

The Connecticut Skeptic Vol.1 Issue 2 (Winter '96)

    It was late at night; I awoke and saw a shape at the end of my bed.  As the shape floated closer I could see that it was an old ugly woman. I tried to move but I was paralyzed. She moved onto my chest,  I could feel her weight on me and I could smell her breath. I tried to move and scream but I couldn't. Suddenly, when I thought I could not take any more, she disappeared.
 
    The above scenario is not an atypical one in paranormal literature. Many accounts involve sensing a presence, hearing footsteps, and the inability to move. Another common element of visitations is their occurrence at night while going to sleep or early in the morning upon waking from sleep. This characteristic is very important because it points to a more reasonable explanation than a paranormal one; that of a waking dream or hypnogogia.
 
    Hypnogogia is a well described neurological phenomenon that can occur when one is waking up (hypnopompic) or going to sleep (hypnogogic). It is an in-between state where one is neither fully awake nor fully asleep. In this state very realistic images and sounds can be experienced. Although visual and auditory hallucinations are most common, experiences can range from hearing your name whispered to ones involving all the senses, including touch. They are in essence dream images that are occurring while you are awake. These waking dreams can be bizarre and terrifying and as such are often referred to as night terrors.

     Also associated with hypnogogia is temporary paralysis. Normal sleep contains periods of REM (rapid eye movement-dream sleep) during which the brain stem inhibits, or turns off, the motor neurons in our spinal column, preventing any movement except for the eyes. Normally, this only occurs during dream sleep. The apparent reason for sleep paralysis is our safety. Without this safeguard, we would act out anything we were dreaming and most likely injure ourselves. Paralysis persists during waking dreams because the affected neurons have not been reactivated immediately as they normally should. Therefore waking dreams are in a sense a fusion of normal wakeful consciousness and the distinctive characteristics of dream sleep. We are indeed awake but the paralysis and bizarre imagery typical of dreaming have not yet loosed their hold.
 
    Many sleep specialists are familiar with hypnogogia and sleep paralysis. They frequently encounter a sleep disorder called narcolepsy in which sufferers can, within moments and at any time of day, drop into REM-dream sleep (referred to as decreased REM latency). Other symptoms include excessive daytime sleepiness, cataplexy (sudden weakness often resulting in dropping to the ground), disrupted nighttime sleep, paralysis, and hypnogogic imagery. These last two symptoms, however, occur in 6-10% of the population independent of any pathology.  They can often occur in normal individuals who have had recent sleep deprivation.
     Reports of apparent waking dreams can be traced back to the Middle Ages when men and women recorded nighttime visitations of a sexual nature by demons called a succubus or incubus. In Newfoundland this visitor was called an Old Hag due to its frequent resemblance to an old woman. In the 19th century they were thought to be witches. Each culture and time interprets events in light of their outlooks and beliefs. Today, many people conclude that they have been visited by aliens. A textbook example can be found in Whitley Streiber's book Communion in which he describes waking up in the middle of the night, feeling paralyzed, and seeing strange alien-like beings.
 
    All too often, people jump to an extraordinary explanation for an apparently extraordinary event. They rarely consider the more mundane but much more likely possibilities. Even if they do consider them, they quickly discount them in favor of the more fantastic and appealing option. The principle of Occam's Razor can help us in situations like this. This principle states that when choosing between two or more competing theories each of which can explain the observed facts, choose the simplest for it is the most likely to be true. This does not mean that the simplest theory is always right, but there is no need to believe a complicated theory if a simpler one does just as well.
 
    Hypnogogia is a well understood neurological phenomenon which provides a compelling and elegant mundane explanation for many claims of alien or supernatural visitations.  Of course, it is impossible to prove that all such claims are the result of hypnogogia.  The burden of proof, however, is on those making supernatural or extraordinary claims to prove that their experiences are not due to hypnogogia, or other natural or commonplace causes.  Also, it is easy to imagine how an individual who has had a hypnogogic hallucination with sleep paralysis, and who is not familiar with the neurological cause, will likely interpret their strange experience in terms of their cultural beliefs.  Hypnogogia is therefore an excellent example of how resisting the temptation to accept emotionally appealing and fantastical explanations even for very bizarre experiences, and determinedly searching for a scientific explanation, can lead us out of superstition and into the light of reason.