Anthropologically speaking, the concept of souls lingering on this plane after the body dies is widespread in almost every culture. These may be benign or malignant, the latter often seen as starving or jealous of the living.

Poltergeists (“noisy spirits”) are said to make noise, move objects and appear as apparitions. These apparitions generally resenble humans, but are tranparent and sometimes able to move through walls/objects. Ghosts may also represent the souls of people who have died in a sudden or tragic way and are unable to move onto the next life because of unresolved issues or a desire for vengeance. Other sinister presences may be attributed to demonic forces or other supernatural creatures.

Scientists and paranormal researchers have been trying for decades to quantify and rationalise the countless ghost sightings which occur every year. Some of the earliest tangible proof of the existence of disembodied spirits came from the work of William H Mumler, who was an American spirit photographer active in the 1860’s and 70’s. Mumler’s portraits showed several people accompanied by pale translucent beings in the background of the picture when they were developed. The most famous one of these is of Mary Todd Lincoln with the spirit of her husband Abraham Lincoln. Mumler was later claimed to be a fraud, using double exposure to take advantage of people suffering from grief and clouded judgement.

Several houses all over the world are purported to be haunted, eg. The Lizzie Borden house in America; the site of a double murder, and the Hollywood sign; which actress Peg Entwistle jumped off to commit suicide. The inhabitants of these houses may be suffering from a host of ailments which would explain their claims.

Some scientists have reported a link between geomagnetic changes in the earth’s crust and activation of the temporal lobe of the brain. Stimulation of this area of the brain can cause the person to feel vigorously religious or feel as if there is an ethereal presence in the room. It can also cause hallucinations which take the form of pop culture motifs, most commonly UFOs and aliens.

Low frequency sounds may also be responsible for the subjective feelings of a haunting. Sounds lower than 20 hertz are generally inaudible by humans, but can create feelings of anxiety, sorrow, the chills or the sensation of being watched.

Carbon Monoxide poisoning can also cause abnormalities in visual and auditory perception. Symptoms of poisoning include listlessness, depression, dementia, emotional disturbamces and hallucinations. Phenomena associated with haunted houses including strange visions and sounds, feelings of dread and the sudden and inexplicable deaths of the occupants can be attributed to carbon monoxide leaks from furnaces or gas water heaters.

Pareidolia is the tendency to see patterns within random perceptions. Fpr example, shadows or tricks of the light can be seen to resemble human faces. In other cases, people who expect or want to see ghosts can inaccurately attribute everyday events to supernatural causes, like changes in air pressure resulting in doors slamming, or the headlights of a car reflected in mirrors perceived as sudden flashes of light. In addition, peripheral vision is very sensitive and can be easily mislead, especially at night or when the person is tired – this would account for ghostly apparitions being seen “out of the corner of the eye”.

More research is needed, but as yet, there is no definitive evidence to confirm or deny the existence of ghosts. Subjective experience is the only experience we have of paranormal phenomena and it is yet to be disproven.