Why do people see ghosts?
Psychologists refer to it as the “sensed presence.”
The sensed presence usually happens to individuals who have become isolated in an extreme or unusual environment, often when high levels of stress are involved. These individuals report a perception or feeling that another person is there to help them cope with a hazardous situation. The vividness of the presence can range from a vague feeling of being watched to a clearly perceived, seemingly flesh-and-blood entity such as Clooney’s character in Gravity. This entity might be a god, a spirit, an ancestor, or someone personally known to the observer. Sensed presences usually appear in environments with little variation in physical and social stimulation; low temperature is also a common ingredient.
Possible explanations for a sensed presence include the motion of boats, atmospheric or geomagnetic activity, and altered sensations and states of consciousness induced by changes in brain chemistry triggered by stress, lack of oxygen, monotonous stimulation, or a buildup of hormones. There is in fact exciting new evidence from a research group led by Olaf Blanke demonstrating that it is the precise stimulation of specific brain regions that tricks people into feeling the “presence” of a ghostly apparition.
Environmental psychologist Peter Suedfeld also thinks that what we do cognitively changes under these circumstances and may play a role.
Suedfeld proposed that we normally spend most of our time attending to and processing external, ambient stimuli from the physical world surrounding us. However, persistent exposure to stimuli that we are evolutionarily unprepared to process, or a lack of change in our surroundings, may cause us to focus more within ourselves, which most of us are much less experienced at doing.
Seeing ghosts may also be triggered by the “agency-detection mechanisms” proposed by evolutionary psychologists. These mechanisms evolved to protect us from harm at the hands of predators and enemies. If you are walking down a dark city street and hear the sound of something moving in a dark alley, you will respond with a heightened level of arousal and sharply focused attention and behave as if there is a willful “agent” present who is about to do you harm. If it turns out to be just a gust of wind or a stray cat, you lose little by overreacting, but if you fail to activate the alarm response and a true threat is present, the cost of your miscalculation could be high. Thus, we evolved to err on the side of detecting threats in such ambiguous situations. A recent study by Kirsten Barnes & Nicholas Gibson (2013) explored the differences between individuals who have never had a paranormal experience and those who have. They confirmed that experiences of supernatural phenomena are most likely to occur in threatening or ambiguous environments, and they also found that those who had paranormal experiences scored higher on scales measuring empathy and a tendency to become deeply absorbed in one’s own subjective experience.
Most likely, the experience of the sensed presence is the result of many of these factors interacting at once.
The tone of the article suggests that people see ghosts even though ghosts can’t be real.
The evidence of parapsychology is that some reports of ghosts have a physical, factual basis.