Childhood slumber parties and nights spent camping out in the back garden with friends telling ghost stories mean that when spooky experiences happen, people think first of the paranormal and then of more boring explanations. Evolution has produced a population who jump at shadows when they're alone, because braver souls were eaten by tigers leaping out of the dark before they could pass their fearless genes onto their descendants.
"The correlations between ghostly activity and magnetic variance were relatively large and tie in with laboratory findings that suggest varying magnetic fields have a measurable effect on human physiology."
Dr Paul Stevens, Koestler Parapsychology Unit at Edinburgh University.
Malevolent shadow at the end of the bed
A bed is supposed to be a warm and comfy place to snooze, surrounded by soft pillows and securely closed doors, safe in the knowledge that the outside world is locked out. When you drop off to sleep, only to wake up with an evil, dark presence standing at the end of the bed, staring at you with ill intentions, the experience can scare the pants off you, especially as you are normally frozen in place, unable to move and run away, almost catatonic with fear.
Demonic presences looming over a sleeping person, or even leaning on their chest or choking them have been part of ghostly lore for centuries. Modern science, though, has come up with evidence that points toward a completely natural explanation that offers some crumb of comfort to those paralysed people lying in bed waiting for the demonic presence to come and kill them in some horrible way. It's called sleep paralysis, and it is an accidental side effect of a generally helpful characteristic of the sleeping body. Normally, the body switches off movement when it sleeps, to prevent problems like sleepwalking, and when a person wakes up, this paralysis turns off. Those threatening faceless presences next to the bed are artifacts created by the brain in sleep mode, and the person only sees and remembers them when he wakes up but is still stuck in paralysis mode, so he cannot move or scream.
Communication through a ouija board
Talking to the dead through the ouija board is a rite of passage for all impressionable teenagers, especially those who try and talk to one particular person who they think died in a murderous rampage. When the planchette starts to move, though, and the otherworld appears to start communicating, the fun can soon wear off and the fear starts setting in.
The ouija board works on the principle that a ghostly presence guides the hands of the living to the letters and 'Yes' or 'No' symbols written on the board. In reality, though, many oujia sessions are guided by the actual hands of real live people who want to mess with their friends' heads. Other times, as Scott Eberle Ph.D, writing for Psychology Today says "....we select the letters ourselves in this game; it’s just that sometimes we don’t quite know that we do it or how we do it." This subconscious desire to produce a communication can be easily proven by blindfolding the ouija board participants and moving the board so the people supposedly channelling the ghost can't see where the planchette goes to.
Ghostly apparitions and feelings of dread
Cold drafts from nowhere and a chill on the back on the neck can signal ghostly presences, and when an apparition materialises, belief in ghosts can be cemented. Although rare, these sightings and feelings of dread can actually be explained by normal phenomenae, albeit not very well known ones.
A weirdly scientific explanation for sudden feelings of fear and doom is that sound frequencies below the level of human hearing can affect the emotions and produce unexplained feelings of depression, fear and even dizziness. These frequencies can also act on the eyeballs to produce vibration, which in turn can create visual hallucinations of objects like ghostly shadows. Electromagnetic field variations can also interfere with normal ability to sense the environment, contributing to a weird interpretation of the immediate environment. "When we measure houses where pervasive haunts occur, the place where the occupants find they can sleep, by trial and error, has the most consistent and normal field strengths," says Dr Michael Persinger of Laurentian University, Ontario, Canada. Simple eye disorders like cataracts are also responsible for hallucinations, because the clouded vision of the person affected can trick the mind into seeing things and people that aren't really there. Drug use and psychiatric problems are also potential causes of seeing and feeling things that aren't really there, and even the most cynical person can start jumping at shadows and mistaking noises for footsteps, if the environment is dark and eerie enough.
Seeing or hearing ghosts may be a sign that something is up with the body, and a check-up may be in order, in case issues like cataracts, narcolepsy or other serious issues may be present. Sleep paralysis, on the other hand, happens to lots of people, and is completely normal and not dangerous in any way, although it is very scary.