As a child, I developed an interest in ghost stories. I was frightened and intrigued by tales of people who saw dead relatives appearing before them. Of course, as I’ve grown up, I’ve become a man of science. A man of cold hard logic, logic which destroys any element of the incredible or fantastic that can be found in the human imagination, leaving me with a forlorn and joyless life experience.

Recently, I’ve been reading another general neuroscience tome, this one called “Mapping the Mind,” and it has an interesting look at what scientists know about hallucinations. This knowledge goes a long way towards explaining what people throughout history have referred to as ghosts. Consider the following cases…

Psychiatrist Morton Schatzman reported the case of a woman called Ruth who was haunted by her abusive father. She would wake in bed and find him leering over her, or walk into her living room and find him ensconced in her favorite chair. Sometimes she would lean over to pick up her baby and find her father’s face superimposed on the child’s. The man was still alive when this happened, but the experience was otherwise very similar to the classic tales told by people who see ghosts, right down to the accompanying feeling of a presence.
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Ruth was subsequently found to be able to create such intense images that they completely blocked out the real world. In one experiment she was linked to a machine that measured the electrical activity created in her brain by certain stimuli. When she was placed in front of the light her brain first reacted in the expected way. But when she imagined a person sitting between her and the light her brain no longer responded to the light waves coming from the bulb. The figure she’d conjured up actually blocked her vision of the world. This image differed from the hauntings in one way only: she knew she had produced it herself. Once she recognized that her father’s unwelcome visitations were similarly self generated, they ceased to be a factor and eventually disappeared.

Other than the odd insinuation that there’s something inappropriate about a father leering at the body of his sleeping daughter, this anecdote seems quite insightful.

Another…

Ms B, a retired schoolteacher whose case is reported by a doctor in Bristol, first saw her ‘other self’ when she returned home after her husband’s funeral. She opened the door to her bedroom and was confronted by a shadowy shape of a woman facing her. Ms B reached out with her right hand to switch on the light, and the figure did the same with her left hand, so their hands touched on the light switch. ‘My hand immediately felt icy cold, and where it touched me I felt as though all the blood drained out of me,’ she told the doctor.
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Ms B. was subsequently visited almost daily by her double. She found that she did not just see the figure — she felt it as well. Just as normal people are aware of two legs, two arms and so on, she was aware of four.

I’ve read about this doppelgänger effect before. The theory is that your brain has a kind of body map which keep track of where you are in space, and this map gets “corrupted” so that a shadow version of yourself is sensed.

The book offers some thought as to what causes these kinds of hallucinations.

Phantom sights and sounds are particularly likely to occur when people are deprived of normal outside sensory stimuli. People who lose all or part of their sight or hearing often find that they experience hallucinations for this reason. It also explains why ghosts are more commonly seen at night. In the absence of competing visual stimuli the brain picks up the shadow in the corner and molds it into a sinister figure clothed with whatever visual associations — monk’s habit, funeral gown — leap up from the memory storage areas.

Why does this happen? The brain evolved to keep constant watch on the outside world, sensing, sorting and shaping every stimulus in order to insure that no danger creeps up unannounced, or opportunity pass by unnoticed. It needs to keep active so if the usual stream of clambering external stimuli is turned off, it searches desperately for something to take its place. The slightest sound, sight or sensation is seized upon, amplified and shaped to make something meaningful, and if absolutely nothing comes in from the outside, the brain will generate its own excitement. Hallucinations, like dreams, are part of a continuous cabaret that keeps us primed and ready for action.

So you see, you needn’t fear that sinister apparition appearing in the corner of your eye — the ghostly man holding the razor-sharp butcher’s knife. Even as he comes closer, you know he is merely a mentally created façade.

NO, WAIT! I WAS WRONG, THAT’S A GENUINE SERIAL KILLER. GET OUT OF THE HOUSE! GET OUT OF THE HOUSE!