In a study published in 1988, [Michael] Persinger compared thirty-seven years of dated Fate magazine haunting reports with geo-magnetic activity for those dates. He found a nice correlation, and he wrote up his findings in Neuroscience Letters. In a similar study three years later, University of Iowa psychologists Walter and Steffani Randall examined monthly fluctuations in solar winds (which influence the earth's geomagnetics) to see if they mirrored monthly ups and downs in "humanoid hallucinations" culled from old Society for Psychical Research records. Indeed, both showed peaks in April and September, with a trough between.
Persinger then turned his attention to man-made electro-magnetic fields (EMFs). In 1996, a Sudbury coupe had contacted him about strange goings-on in their house. They heard breathing and whispering sounds and at one point felt something touching their feet as they lay in bed. The husband saw an apparition of a woman who appeared to move through the couple's bed. Persinger and two colleagues drove out to the house and set up equipment to monitor EMFs in the various rooms. True to his theory, the house was an electromagnetic free-for-all. Wires were poorly grounded and circuits over-loaded with electronic equipment. Not only were the EMFs most intense in the places where the couple had experienced their "ghosts", but they showed the telltale irregularities that Persinger has come to see as the hallmarks of haunt-prompting fields.
—Mary Roach, Spook: Science Tackles The Afterlife