It’s Halloween, so there are a lot of fluff pieces about ghosts and similar phenomena circulating in the media. There are some good skeptical pieces as well, which is always nice to see. For this piece I did not want to frame the headline as a question, which I think is gratuitous, especially when my regular readers know what answer I am going to give. The best current scientific evidence has a solid answer to this question – ghosts are not a real scientific phenomenon.

For most scientists the story pretty much ends there. Spending any more serious time on the issue is a waste, even an academic embarrassment. But for a scientific skeptic there are several real and interesting questions. Why do so many people believe in ghosts? What naturalistic phenomena are being mistaken for ghostly phenomena? What specific errors in critical thinking lead to the misinterpretation of experiences as evidence for ghosts? Is what ghost-hunters are doing science, and if not, why not?

The first question is mostly sociological. A recent survey finds that 41% of Americans believe in ghosts, and 20% believe they have had an encounter with a ghost. We know that there are some personality traits associated with belief in ghosts. Of the big five, openness to experience and sensation is the biggest predictor. Also, intuitive thinking style rather than analytical is associated with a greater belief in the paranormal in general, including ghosts.

The relationship between religious belief and paranormal belief, including ghosts, is complicated. About half of studies show the two go together, while the rest show that being religous reduces the chance of believing in the paranormal. It likely depends on the religion, the paranormal belief, and how questions are asked. Some religious preach that certain paranormal beliefs are evil, therefore creating a stigma against them.

However, religious and paranormal beliefs share some cognitive features (making them mainly competitors within the same approach to belief). This study summarized the data well:

The data were most consistent with a path model suggesting that mentalizing comes first, which leads to dualism and teleology, which in turn lead to religious, paranormal, and life’s-purpose beliefs.

The belief that the mind is a thing unto itself, that reality begins with mental phenomena, leads to belief in a mind separate body and to outcomes influencing causes. This thinking can lead to a host of supernatural beliefs, whether they are part of a mainstream religion or not. On the contrary, a belief in strict naturalism is incompatible with paranormal beliefs (almost by definition).

This leads to another interesting question – are ghostly phenomena inherently paranormal? Can we accommodate ghosts within a scientific view of the universe? Here the answer is also a solid no, at least not as ghost are typically conceived. Ghosts are wispy spirits. They are not made of matter, but of some kind of spiritual energy. This is where dualism comes into play, because ghosts are generally defined as being the “spirits” of people who were once alive. It presupposes that their mental function (memories, personality, knowledge) have survived the death of their physical body, and has a separate existence. There is no credible evidence for this, and no known phenomena that can make this possible. I have written extensively about the fact that the mind is what the brain does, and there is no mind separate brain.  There isn’t even any theoretical mechanism for such a phenomenon.

Ghosts, as typically portrayed, do not conform with what science tells us about how the universe works.  If they are pure energy of some sort, how are they coherent? Why are they not traveling at the speed of light, which pure energy should be doing. How can they interact with the material world sometimes but not others. They pass through walls, but not the floor. How are they held by the Earth’s gravity? The best answer one gets from believers is that ghosts are made of “spiritual” energy, which behaves the way it does. It’s a mystery, and you can’t science it (unless you are a ghost hunter proving ghosts are real).

Which leads to the next question – if ghosts are not real, what are people experiencing when they think they are encountering ghosts? Often this question is framed at skeptics as – do you think they are all lying? This is, of course, a strawman. I think some people are lying, sure. But mostly people are just misinterpreting common phenomena in line with their cultural, personal, and religious beliefs. These common phenomena fall into a couple of categories. The first is what I call “brain glitches”. The human brain is glitchy, it produces phantom experiences and perceptions, is misperceives what is out there, it misremembers what it experienced, and it is very suggestible. I have personally experienced many brain glitches, including hypnagogic hallucinations and phantom voices. They can be very compelling and unusual experiences, and I completely understand how people reach for paranormal explanations. But they are purely internal experiences.

It is no coincidence that many such experiences happen when people are sleep deprived, or transitioning to or from sleep, or otherwise cognitively impaired. Sometimes, however, people’s brains are functioning “normally”, but the environment is unusual and produces ambiguous stimuli that the brain struggles to properly interpret. We may hear voices because our brains are constantly trying to interpret sounds as speech, and can overmatch ambiguous sounds into the closest match, for example (auditory pareidolia).

But brain glitches don’t explain physical evidence. What about all the photos, recordings, EM signatures, temperature drops, and other things recorded by ghost hunters? Now, of course, we are solidly in the realm of science. What ghost hunters are doing, however, is not science. It is classic pseudoscience. Their method is not to generate a hypothesis and test it in such a way that the hypothesis can be shown to be wrong. Rather, they simply combine anomaly hunting with the sharpshooter fallacy. Anomaly hunting means, just look for anything unusual (very loosely defined, and often defined after the fact). When something that can be portrayed as an anomaly is found, they then declare that evidence of a ghost, whatever it is. A cold spot becomes “ghost cold” (in the words of Ed Warren, one of my early skeptical investigations).

This is not scientific evidence. Beyond just anomaly hunting, they largely ignore or dismiss the many mundane explanations that are much more likely. There are electromagnetic readings (in whatever EM range your detector happens to detect) because EM radiation is ubiquitous. Lots of things in a typical house (even without electricity) can set off an EM meter. Houses, especially old houses, have cold spots. If you stop and listen you will find that almost every location is accompanied by strange noises. There are many reasons why blobs of light might appear on pictures, many documented and proven by skeptical investigators. In short, there are mundane explanations for all of it.

In short, ghosts do not make sense as a scientific phenomena, there is no evidence they are real, ghost hunters are not doing real science, and belief in ghosts can be tied to cognitive style and misinterpreting mundane neurological and other phenomena. Or – ghosts are not real.

Happy Halloween.

(Note: I am at NotACon this weekend, so no further posts until next Monday)