This is just the basic info, I'll post more in depth stuff later....
Shadow people (also known as
shadow figures,
shadow beings,
shadow men, or
shadow folk) are
supernatural shadow-like figures of both modern
folklore and
paranormal popular culture that believers describe as dark
humanoid forms or evasive specters that are seen mostly in
peripheral vision.
[2][3]
Several principles based in science can be used to explain reports of shadow people, including
optical illusions or
hallucinations brought on by physiological/psychological circumstances, drug use, and the interaction of external agents on the human body.
When a specific region of the brain called the left temporoparietal junction is stimulated, it can create the illusion of a shadow person.
[6]
Images seen in
peripheral areas of vision can be caused by
pareidolia, a condition in which the brain incorrectly interprets random patterns of light/shadow or texture as being familiar patterns such as faces and human forms.
[7] The same condition can also be observed in macular vision in low light conditions, or when viewing a complex but random image. A common example would be perceiving a shadow, thrown by an item of furniture in a darkened room, as being a person.
Hypnagogia,
also known as "waking-sleep", a physiological condition in which a person is part-way between sleeping and waking, can also account for such perceptions.[8] During hypnagogia, a person can be conscious and aware of their environment, but also in a dream-like state where they can perceive images from their subconscious. People experiencing waking-sleep commonly report the sensation of lights or shadows moving around them, as well as other visual hallucinations. A feeling of
dread is also a sensation that occurs when experiencing hypnagogia. Hypnagogia is sometimes known as 'the faces in the dark phenomenon' because those who experience this state commonly report seeing faces while experiencing waking-sleep.
[9] Similar hypotheses have been put forward linking this condition to a number of other apparent paranormal experiences, including
alien abductions, paranormal nocturnal visitations, and religious experiences such as contact with angels or demons.