Popular term for supposed apparition of the dead. (Psychical researchers tend to use the term apparition.) Ghosts are often depicted as resembling human form and described as fog-like, misty, silver, transparent and the like. They can be visible but they can also make their presence felt with strange noises, smells, cold air, the switching of lights on and off and by movement of objects.

The ancient meaning of the term ghost typically refers to the disembodied soul, which after death is thought to travel to the underworld or afterlife. Beliefs vary as to what happens to the soul after death but virtually every culture has believed at some point that the ghost can return to the world of the living and when they return they can have either good or bad intent.

In the West, those who believe in ghosts sometimes hold that they are the souls of those who cannot find peace in death or realize they are dead, and so they linger on earth. Their inability to find peace is often explained as a need to deal with unfinished business, to deliver advice or information, to protect or stay close to loved ones or simply to re-enact death (see Grateful dead). In some cases the unfinished business involves a victim seeking justice or revenge after death. The ghosts of criminals are sometimes thought to linger to avoid purgatory, hell or limbo.

In Asian cultures (such as China) many people believe in reincarnation and ghosts are thought to be souls that refuse to be reborn because they have unfinished business, similar to those in Western belief. In Chinese belief ghosts can also become immortal, or they can go to hell and suffer forever, or they can die again and become a ‘ghost of ghost’.

Every culture has superstitions and beliefs about ghosts but both the West and the East share some fundamental ideas. There are often procedures and rituals for dealing with troublesome ghosts, such as exorcism. Ghosts may wander around places they frequented when alive, or where they died. Contrary to popular belief most ghosts are not reported at graveyards where the body may be buried but in houses and buildings where a person may have died, suffered or lived for many years.

Many ghosts are reported when conditions are foggy and could well be explained as tricks of the light, just as those reported during thunderstorms may be caused by electrical charges in the atmosphere. Although there are reports of appearances during the day, the majority seem to appear at night. It’s possible that a person is more sensitive to clairvoyance when relaxed or asleep at night – many ghosts also appear during dreams. However, some believe that ghosts reported to have been seen at night when a person is wide awake may actually be hallucinations that occur when they are drifting off to sleep.

While some believe ghosts to be an objective reality, sceptics argue that there is always a simple explanation.First of all the the sincerity and motive of the person reporting the haunting will be called into question – there have been instances when reputed sightings of ghosts has been fabricated as a scare tactic to seek justice or revenge. The possibility of a hoax or con is considered, and then explanations grounded in knowledge about human physiology are offered. For instance, the appearance of ghosts is often associated with a chilling sensation and pale, semi-transparent apparitions. But a natural response to fear is hair-raising, which can be mistaken for chill, and the peripheral vision is very sensitive in detecting motion but does not contain much colour or provide focused shapes; therefore, movement outside the focused view, such as a moth darting towards a light or a curtain moving, can create a strong illusion of an eerie figure. And certain infrasonic frequencies are known to create unexplained feelings of anxiety or dread, which are so often associated with sightings of ghosts. Finally, psychological factors are often cited as natural explanations for ghost sightings: susceptible people tend to be prone to exaggerated interpretations of sensations or feelings they experience when visited a reputed site of haunting.

Frederick Myers, one of the founders of the Society for Psychical Research in London, believed that ghosts were ‘manifestations of persistent personal energy, or an indication that some kind of force is being exercised after death which is in some way connected with a person previously known on earth’. Myers believed that ghosts were projections of consciousness without a conscious identity, but more recent research has argued that ghosts may possess some kind of awareness.

Ghost investigators have found that in the majority of cases there are natural explanations for sightings, but this still leaves a tiny number – perhaps as small as 2 per cent – that just can’t be explained naturally, however sceptical or unconvinced the investigator. There is as yet no definitive answer as to whether ghosts are genuine or figments of the imagination, or if they have personality or are flashbacks of the past.

See also Ghost investigation.