Why Do People See Ghosts?

By Daniel Kolitz on at

You live and then you die and then you rot in a hole—or so say the elites, with their glasses, and their PhDs in neuroscience. This bummer reality has never appealed much to Americans, 72% of whom believe in some kind of afterlife. It’s a comparatively rarer, though still sizeable, breed of American who believe in some spectral middle ground, in which, instead of rotting or going to hell, you float around and freak out your kids, or the new residents of the house where you were brutally murdered a hundred years ago.

According to Pew Research Center, close to one-fifth of Americans believe they’ve seen a ghost—a somewhat surprising statistic, given all the other ancient beliefs we’ve mostly jettisoned (bloodletting, for instance, has largely fallen out of vogue). For this week’s Giz Asks, we reached out to a number of psychologists and neuroscientists to figure out why this might be—and in the process learned that, given the number of ways our brain has of tricking us into seeing things, it’s a wonder that that statistic isn’t higher.

Christopher French

Founder of the Anomalistic Psychology Research Unit at Goldsmiths, University of London

Most of the time, when people think they’ve had a ghostly encounter, they haven’t necessarily actually seen something. Very often you’ll find that what people are referring to is a bit vaguer than that—a very strong sense of presence, for instance. Bereaved people might think that they smell the perfume that the deceased used to wear, or the tobacco they used to smoke.

People tend to assume, when you suggest that maybe they were hallucinating, that you’re saying that they’re crazy, and this just isn’t true—hallucinations are much more common amongst the non-clinical population than is generally appreciated. We can all hallucinate under appropriate conditions.

One of the phenomena that we’re particularly interested in is something called sleep paralysis. In its most basic form, sleep paralysis is very common. Estimates vary, but typically it’s estimated that about 8% of the general population suffer from basic sleep paralysis at least once in their lives, and a couple of groups—psychiatric patients and students—show it at a much higher rate.

What I mean by basic sleep paralysis is: You’re half awake and you’re half asleep—either going into sleep, or maybe coming out of it—and you get a period of temporary paralysis. It typically lasts a few seconds before you snap out of it. Most of the time it’s not a big deal—it’s a little bit disconcerting, that’s all.

For a smaller percentage of people, you get associated symptoms that can make for a much scarier experience—typically, a very strong sense of presence. Even if you can’t see or hear anything in the room with you, you get a very strong sense that there is something there. You might actually also hallucinate; you might hear voices, or footsteps, or mechanical sounds, or you might see dark shadows moving around the room, or lights, or monstrous figures, or shadow people. You might get tactile hallucinations—you might feel as if you’re being held, or you might feel someone breathing on back of your neck. And bear in mind that throughout all of this, you can’t actually move.

So it’s not too surprising that lots of people who have this experience, if they’ve never heard of sleep paralysis as a scientific and medical concept, end up reaching for some kind of supernatural interpretation. And because it’s such a common experience, you only need a small percentage of people who are having sleep paralysis to go for those kinds of supernatural interpretations.

Michael Nees

Assistant Professor, Department of Psychology, Human Factors, Perception and Cognition Lab, Lafayette College

Our phenomenological experiences of the world—the things we believe we see and hear—are actively constructed from limited and incomplete inputs from the physical world. The light that falls upon our eyes and the sound waves that reach our ears often could have resulted from multiple possible physical sources. For example, a vaguely humanoid object in the corner of a dark room could be a person or a ghost, but it could also just be a jacket hanging on a coat rack. To resolve these ambiguities, we actively construct an internal, mental version of the physical world that reflects our own biases and expectations. Sometimes our perceptions do not reflect accurate representations of the physical world. “Pareidolia” is the name for a common category of misperceptions that occur when a random (i.e., inherently meaningless) perceptual experience is interpreted to have meaning. A common version of pareidolia is perceiving human faces in random configurations of physical objects; a classic example is when people claim to see the face of Jesus in a piece of toast.

Some researchers have suggested that we may be biased toward perceiving ambiguous stimuli as human or human-like, because detecting other human beings in our presence has adaptive value—meaning that, from an evolutionary perspective, other people are especially important stimuli for us to notice. According to this argument, a false alarm (mistakenly perceiving a random, inanimate object—perhaps momentarily—as human) is less harmful than a miss (failing to notice another actual human in one’s presence), thus, when faced with uncertainty, our perceptual systems are calibrated to be more likely than not to register an object as human.

There is some research to indicate that people who are prone to paranormal beliefs are especially likely to attribute human characteristics to ambiguous stimuli, and researchers have suggested that a spooky context or the suggestion of a paranormal situation can prime people to be more likely to interpret ambiguous stimuli as ghosts or poltergeists.

Neil Dagnall and Keith Drinkwater

Neil Dagnall is Reader in Applied Cognitive Psychology at Manchester Metropolitan University, researching anomalous psychology and cognitive psychology; his lab is undertaking several projects centering on belief in the paranormal

Ken Drinkwater is Senior Lecturer at Manchester Metropolitan University who studies paranormal belief

The survival hypothesis proposes a disembodied consciousness (soul) survives bodily death. Seeing ghosts in this context confirms belief in life after death and produces reassurance.

Other explanations draw on environmental factors, such as electromagnetic fields and infrasound. Canadian neuroscientist Michael Persinger demonstrated that the application of varying electromagnetic fields to the temporal lobes of the brain could produce haunt-like experiences (perception of a presence, feeling of God, sensation of being touched, etc.).

Haunt-like perceptions can also arise from reactions to toxic substances. Albert Donnay (Toxicologist) hypotheses that prolonged exposure to a range of substances (carbon monoxide, formaldehyde, pesticide, etc.) can produce hallucinations consistent with haunting. Similarly, Shane Rogers (Associate Professor of Civil & Environmental Engineering) reported that fungal hallucinations caused by toxic mould could stimulate haunting-related perceptions.

Professor Olaf Blanke recently demonstrated that haunt-like illusions could arise from perceptual disorientation. Specifically, conflicting sensory-motor signals. Blindfolded participants performed hand movements in front of their body. A robot imitated the moments in real time by harmoniously touching the participants’ backs. The synchronized movement of the robot allowed participants to adapt to spatial discrepancy. However, temporal delay between participant’s movement and the robot’s touch produced disorientation accompanied by strong feeling of a presence.

Terence Hines

Professor of neurology at Pace University and the author of Pseudoscience and the Paranormal

The human brain has evolved to find patterns. If you’re in the wilderness, and you hear something behind you, it’s way better to think that it’s really a lion or a sabertooth tiger sneaking up on you—to attribute that sound to some agency, something that has purpose. Because if it does have purpose, and you run away, you’re better off. And if it’s just random noise and you run away, there’s no foul, it doesn’t really cost you anything. So we’ve evolved to experience what neuroscientist types call false positives. It’s better to be safe than sorry.

[Another explanation] involves expectations, and there a couple of lovely demonstrations of this effect. Some years ago, for a term project, one of my students took some people to a local graveyard. In one condition, people were taken to a particular grave and told, this is the grave of some old guy who died at 72 of natural causes. Nothing weird about it. This is late at night, midnight. And they would ask: what do you feel? Are you getting any sensations? And people said well, no, not really. And then in the other condition they took people to the same grave at about the same time, late at night, and said it was the grave of a teen girl who died tragically—she’d killed herself after her boyfriend left her, and she’s said to haunt this grave at midnight on the night in question, and this is the anniversary of her suicide. People freaked out. They saw her, they heard her—and it was all due to expectations. I’m not saying that the folks who experienced the ghost of this non-existent teenage girl were lying, or crazy, or hysterical—they weren’t. Their brain was just doing what brains do; they were using information they were given, which turned out to be incorrect.

Tapani Riekki

Cognitive neuroscientist, Department of Psychology and Logopedics, Faculty of Medicine, University of Helsinki

The key thing seems to be interpretation. We know from various studies that our information processing is not “bottom-up”—we don’t just see/hear/feel our environments. Instead, our perception of reality is a complex interplay between bottom-up and top-down processes. Top-down processes refer to the expectations, beliefs, and context that shape our perceptions and influence our interpretations. Even the basic bottom-up processes are not exact copies of reality but approximations shaped by context. How we experience our surroundings is a complex simulation of our mind that leaves a lot of space for interpretation and quirks.

Frank McAndrew

Cornelia H. Dudley Professor of Psychology at Knox College and an elected Fellow of the Association for Psychological Science

Seeing ghosts may 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.

In other words, if an individual believes that an encounter with a ghost is a possibility, then ghosts may become the explanation that gets used to resolve uncertainty.

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.

Benjamin Radford

Benjamin Radford, M.Ed., is a Research Fellow with the Committee for Skeptical Inquiry, a non-profit educational organization based in Buffalo. He has researched ghostly and “unexplained” phenomenon for nearly 20 years and is author of several books on the topic, including “Investigating Ghosts,” out this fall.

When researching ghostly phenomena one of the first things you realize is that often “ghost” is simply a convenient (if sloppy) label for “an experience someone doesn’t understand.” Reports of full-bodied apparitions (the kind you might see at Disneyland’s Haunted Mansion, for example) are very rare. Instead you find that many “ghostly” experiences are much more ambiguous: odd smells or sounds, a feeling of being watched, temperature variations, animals acting up, and so on. Even such mundane experiences as losing your keys can be—and have been—chalked up to the doings of a mischievous resident spirit.

Because there’s such a wide variety of experiences attributed to spirits, there’s no single blanket explanation for all ghost reports. Some can be caused by mild hallucinations—I’m not talking about over-the-top, full-on wild LSD-type hallucinations of flying pink elephants, but instead much more common and subtle tricks of the eye and mind, especially that might occur late at night. The human brain is wonderful but also fallible, and we don’t always perceive and interpret the world around us correctly—and because many “ghostly” experiences are small and fleeting (not the huge and obvious kind depicted in horror films), it’s easy to wonder if an odd sound or light is mysterious. This leads to the second common factor as to why people believe they’re experiencing ghosts: usually they’re influenced by pop culture ideas about what ghosts are and how they act. People watch TV shows like Ghost Hunters (now past its tenth season of not finding ghosts) and are influenced by those shows in terms of what psychologists call priming. Our expectations often guide our perceptions and interpretations, and thus we often see or hear what we expect to see—sometimes even if it’s not there. The psychological reasons behind why people claim to (or believe that they see) ghosts is well understood—and that’s true whether ghosts exist or not!