If you happen to see ghosts on Christmas eve, it might not be as Charles Dickens writes in A Christmas Carol. It might be your brain fooling you.

Most scientists dismiss the vast majority of ghost sightings as hoaxes. But researchers in Canada, England and elsewhere are exploring what happens in the brain to create the illusion that something is "haunted."

So far, they have found evidence that some apparitions may be brain benders caused by spiking EMFs (electromagnetic fields), and possibly even extremely low-–frequency sound waves (known as infrasound) so subtle that the ear does not register them as noise.

EMFs emitted by power lines and towers, clock radios and other electrical sources may help debunk myths that people or things are haunted, says Michael Persinger, a neuroscientist at Laurentian University in Sudbury, Ontario, Canada, who has conducted research on the topic. One such study, published in 2001 in Perceptual And Motor Skills chronicles the experiences of a teenager who in 1996 claimed to be receiving nocturnal visits—one sexual—from the Holy Spirit. The 17-year-old girl, who had sustained mild brain damage at birth, said she also felt the presence of an invisible baby perched on her left shoulder.

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Ebenezer Scrooge encounters "Ignorance" and "Want"
in A Christmas Carol.