Nocturnal Encounters
Sleep Paralysis and Nightmares as Related to Ghostly Appearances

Many encounters with the supernatural are preceded being asleep. The typical testimony will include statements such as;

I woke up and sensed something in the room with me
I was unable to move
The figure standing there was blurry maybe it was a dream
I was unable to breathe as if someone or something was sitting on my chest
I could hear something unnatural moving about
I knew it was an evil entity

When investigating ghostly encounters we are faced with the problem of whether the source of the apparition was external (ghosts and spirits) or internal (nightmares and/or hallucinations).  The internal aspect is associated with a sleeping disorder known as Sleep Paralysis (SP) and the sensory experiences that accompany SP are referred to as Hypnagogic/Hynopompic Experiences (HHE).
 The Dream State of the sleeping cycle is identified by Rapid Eye Movement (REM). The eyes move about in an attempt to scan the images that are generated in the visual areas of the brain. Another condition associated with REM is that the body becomes atonic (lacking muscle control).  This is a natural function that prevents the body from reacting to what is seen in the dream. Without this we would probably awake every morning battered and bruised, not to mention the damage done to our partners. Upon waking muscle control is quickly regained except during SP.  It is suspected that the bodies ability to wash out the atonia is compromised. This state of paralysis is often interpreted as a feeling of being restrained or being frozen with fear. SP can also be accompanied by difficulty or shortness of breath, which accounts for reports of being sat upon or feelings that some great weight is pressed on the victim.
 
 Most individuals that experience SP also have HHEs. These are defined as hallucinatory states, hypnogogic refers to sleep onset and hypnopompic to wakening. A hallucination has to have several qualities:

1) It has to have the sensation of being caused by an event
 externally not in ones head.  Not just imagination or
 an idea.
 
2) The cause of the event is beyond the control of the
        percipient.
 
3) The event has to feel real enough that the percipient
believes it could be verified by an independent
observer.
 
 It is not clear whether the hallucinations are a result of the mind trying to sort out the possible cause of the symptoms along with the heightened anxiety of being paralyzed or whether the hallucinations are intrinsic part of SP.
 
 There are common features to sleep paralysis and hypnagogic/hypnopompic hallucinations.   The percipient has the feeling of being awake and unable to move.  Their eyes open and close and are able to visually scan. Feelings of pressure on the chest are the most common, however, sensations of being held down, choked or smothered have also been reported. There are usually auditory experiences of footsteps, shuffling or breathing. Visual aspects include ghostly forms, amorphic creatures that are indistinct, shadows with eyes that are the most prominent feature and animal likenesses. The feeling of malevolence is the most striking and typical  aspect of this type of encounter. The interpretation of the presence generally is one of evil intent it is death, it is there to do harm or to attack, or even to sexually molest.
 
David J. Huffordís book The Terror That Comes In The Night has many case studies that highlight this phenomenon. He first noticed these symptoms in people that reported being attacked by an "old hag while asleep. The old hag is a common description in Newfoundland.  It is believed that while sleeping this old hag holds you down and if not awakened you will die. Hufford found that people reported the same symptoms in other areas around the world, however, they were interpreted differently as ghosts, demons (esp. incubus/succubus), vampires etc.. This gives rise to the idea that this phenomenon is experience based not culturally based.  An attempt to explain what happened is a synthesis of the experience through cultural knowledge.
 
When doing investigations we inquire about the percipient's dreams and sleeping habits.  It is important to establish any sleep disorders that may account for their sighting(s). Keep in mind that even if someone has had this problem in the past it does not negate the impact or veracity of their statement.  There is still a lot of research to be done into this phenomenon and the exact purpose and process of dreaming. There are many involved in the paranormal that believe that dreams are one possible avenue for the dead to communicate. Any serious investigation should include questions regarding this subject in order to establish a database that may eventually establish a more concrete explanation for this supernatural event.