Some people believe ghosts are spirits. Others dismiss them as hallucination or delusion. But what if they are none of these. What if we take witness statements of ghost sightings at face value - they literally do see the figure of someone who is not physically present. How is that possible without spirits being involved? And can anyone who wants to, see ghosts?

“... when you have eliminated the impossible, whatever remains, however improbable, must be the truth.” Sir Arthur Conan Doyle in the Sign of Four.

Misperception and hallucinations

There are no official statistics but it is clear that most ghost cases, when properly investigated, turn out to be caused by misperception. It is obviously something that must be eliminated first, before anything can be claimed as paranormal. It is therefore important to understand it.

Misperception is misinterpreting something seen, heard, felt or otherwise sensed. It is likely, taking into account the results of many investigations, that misperception alone accounts for the most reported paranormal experiences. Hallucinations, by contrast, originate inside your brain, so they don't require any 'something' in the real world (a sensory stimulus). Between them, misperceptions and hallucinations probably account for a great many reports of apparent paranormal phenomena.

Looking for misperception and hallucination

Hallucination is more difficult than misperception to detect. With no 'sensory stimulus' to look for, detecting hallucination requires examining what was happening to the witness when they experienced the apparent paranormal phenomenon. If they were on the verge of sleep at the time, for instance, you might suspect a near sleep experience. If they felt paralysed then it might be sleep paralysis. Many people experience one or two episodes of sleep paralysis in their lives. Other causes of hallucination include sensory deprivation and absorption. Some other types of hallucination may be caused by medical conditions (like epilepsy) or by taking certain drugs, so you could check witnesses's medical history (see also mindsight). A small number of hallucinations may be induced by such things as certain magnetic fields.

With misperception there is something outside the witness to look for - the sensory stimulus! It would be worth trying to recreate the situation of the original experience, at precisely the same location, to see if the object is obvious. It would be very useful if you could reproduce the lighting conditions too, if relevant, as many misperceptions occur in poor light. If you're lucky, you too may experience the same misperception. Sometimes, though, the cause of a misperception may have gone by the time of the investigation.

Misperception

As optical illusions illustrate, our brains can easily be fooled. Misperceptions are caused by ambiguous, insufficient or conflicting sensory information reaching our brains.

• Ambiguous sensory stimuli may present aspects of different objects, forcing our brains to decide which is really present
• When our brains get insufficient sensory information they may 'edit in' likely objects from memory to make sense of an experience
• Sensory conflicts may arise between different senses which our brains have somehow to resolve

In all such cases, it seems our brains 'resolve' such problems BEFORE presenting sensory information to our consciousness. Thus we are presented with a seamless experience which may, sometimes, not reflect the real world.

In order to understand misperceptions, we must first understand normal perception. Details of the process are still being unraveled by science but we know some relevant things already.

The picture in your head - visual misperception

The most 'acute' of your senses is vision. It is 'acute' because it is the one we rely on the most to form our picture of reality. When our senses receive conflicting information, vision is the one that wins the tussle. Vision also provides more information than any of the other senses, measuring not only the wavelength and amplitude of light (equating to colour and brightness) but also the spatial layout of light sources in three dimensions. By comparison, only frequency and amplitude are measured in hearing.

Consider the 'picture in your head' - that crisp, colourful movie of the world behind your eyes that most people assume is reality. In fact, it is a moving image stored and played in your brain. The whole image is not fed continuously by your eyes but instead it receives brief detailed updates of small parts of the view in front of you. The bits of the image not currently being updated are slightly out of date, being the result of previous updates. The reason is that detailed views can only be obtained from a small bit of your retina, called the fovea. Your eye performs constant jerky movements, called saccades, to point the fovea at the most interesting parts of a scene. The fovea then 'fixates' on a small area while passing information to the brain. During the actual eye movements, little or no information goes to the brain. We generally perform about three saccades a second, each lasting 20 to 200 microseconds. For the remaining time we are fixating on a relatively small area of the scene ahead.

So how is the 'picture in your head' maintained? Recent scientific research suggests that it is partly from updates, partly from short term memory (what was there at the last fixation) and partly from visual long term visual memories. This last bit is particularly interesting from the point of view of misperception. If you see an 'ambiguous stimulus' (something seen that your brain does not immediately recognise from memory or where there are conflicting signals from other senses), your brain needs to make a quick decision. It tries to maintain a picture that 'makes sense', so sometimes it may substitute the ambiguous visual information with something from its long term memory. This happens before the 'picture in your head' is updated, so the substitution is not noticed and feels perfectly real to you, the witness.

Consider, for instance, if you saw a shadow in a dark room, your brain might not have sufficient information to work out what it is. So it might decide it is a human figure. Your long term memory may then add 'details' to the sighting that you can't really see, like limbs or clothes, because of expectation. Your brain knows, from experience, that humans generally have limbs and clothes, so it inserts such 'details', even though your eyes can't see them. Because seeing a strange figure in a dark place can be a disturbing experience, psychological suggestion may come into play making you think it might be a ghost. If the figure doesn't move, as it might not if it is a shadow with a mundane cause, this strange 'behaviour' may reinforce the idea that it is not an ordinary human at all but a ghost. And even people who don't consciously know much about ghosts will have absorbed enough from the culture to inform such a perception.

This process of 'editing' the 'picture in your head' is entirely unconscious. Therefore the image will feel totally real to you and will be remembered as such. The process is probably easier if, whether consciously or otherwise, you accept the idea that ghosts, as well as real people, are possible. This unconscious 'acceptance' may come through cultural memory.

Research has shown that each object in the 'picture in your head' is dealt with separately by your brain. This applies even when two objects overlap. Thus, an object from your visual memory can be 'inserted' into a real scene completely naturally. It might even be partially obscured by another real object. This is one reason why misperceived objects can appear completely convincing and normal!

Different people will be subject to differing misperceptions because each has their disparate life experiences and memories. That's because misperceptions originate in people's long term visual memory. So if three people see an ambiguous stimulus, one may see one ghost, another a different ghost and the third just a shadow! Misperceptions can also vary according to the viewing conditions. Just as with an optical illusion, they may look completely different from a slightly different viewing angle or may disappear altogether. Thus misperceptions are sensitive to (a) who the viewer is and (b) the viewing conditions. This can make them difficult to reproduce.

There are further visual misperception problems related to peripheral vision ('corner of the eye') and low light but they are dealt with elsewhere. For practical advice on detecting misperception in witness testimony, see visual substitutions.

It takes around 100ms for the signals from our retinas to reach our brains. To compensate for this delay, our brains 'predict' any motion we are seeing. Thus our minds will show us where a ball that is flying though the air actually is, rather than where we can really 'see' it. If this didn't happen we couldn't play games like tennis (as we'd try to hit the ball after it had gone). So what we see in 'picture in our heads' is not what is going on right now but a 'future projection' 1/10s ahead, produced by the unconscious parts of our brains! This delay is thought to be the mechanism behind optical illusions, where the brain's projection about where things will be is sometimes wrong.

To produce this 'future projection', our brains have a 'functional model' of how objects, like tennis balls, behave when moving. However, when we see something we have never seen before, or something we mistake for another object, our brains may use the wrong 'functional model' for the object. If we see a tree in bad light, the unconscious parts of our brains may think it is really a ghost. So, we may see it 'move', even when it doesn't, because that's what our brains expect a ghost to do! Our 'functional models' of things like UFOs, which most people have never seen before, may be derived from the movies!

Shadow ghost misperception

Look at the photo, right. It shows a shadow on a stair. The whole photo looks dark. The shadow on the stair bears a passing resemblance to a human figure in its shape and with a 'hand' on the right banister and 'legs' stretching down several steps. If it were a person it would be rather short, a child perhaps. However, if you saw this shadow briefly, without having a photo to study at your leisure, you might think it was a shadow ghost.

There is no shadow ghost in the photo, just the chance way the shadow fell vaguely suggesting the human form. We humans are particularly prone to seeing figures and faces in random patterns, probably from ancient survival skills. Had the shadow fallen in a different way, the effect probably wouldn't have worked. Indeed, for some readers it probably doesn't work now!

The photo was just a normal one of the interior of a building. Nothing has been electronically added to the photo. Instead the whole picture has been simply been darkened and the contrast increased, until the shadow obscures the background, in a photo software package.

The final effect is an ambiguous stimulus - is it just a shadow (as the colour and lack of detail suggest) or a shadowy figure (as the shape suggests)? Your brain has conflicting visual cues to resolve - shadow or figure? If you were to approach such a shadow, it would probably change shape or even vanish (as the angles of the light throwing the shadow changed). Since your brain knows that humans can't do things like change shape or vanish, it might conclude the shadow was a ghost!

Optical illusions (like these) are a common form of misperception. They usually work by providing conflicting, or ambiguous, visual information. The brain has to make a choice which, with optical illusions, is usually wrong. Again, the brain likes to present a 'reasonable' version of the world (based on experience), rather than a totally realistic one, so it is fooled into making mistakes.

Sound misperception

This same kind of process that occur in vision perception happen with sound. If you listen to speech in a noisy environment, your brain will 'fill in' likely sounding words that it didn't actually hear. And with ambiguous sounds, you can hear different things, often determined by expectation and suggestion. Flowing water (a kind of near white noise) can sound like whispering or music in certain circumstances. Once again your brain is faced with conflicting or ambiguous cues and has to make a choice.

These kind of misperceptions occur in formant noise. You can hear illustrations of these sort of aural misperceptions here.

Touching misperception

We have a mental map of our body based on vision and touch. However, vision is more important than touch and conflicts between the senses can lead to misperceptions like the 'rubber hand illusion'. You take a model of a hand and put it on a table in front of you while hiding one of your real hands where you can't see it (behind a screen, perhaps) and holding it in the same pose. Then you get someone to gently stroke both the model and your real hidden hand with the same movements. You will get a strange feeling that the rubber hand in front of you is your own! You can see a demo here. It is possible that the Christos method of inducing out of the body experiences may deliberately induce a conflict between vision and touch to manipulate your 'body map'.

Now imagine you are sitting in the dark reaching out and you can feel something. Without vision, are you sure you know where your hand is in space? It certainly brings into question spatial awareness and apparent touching incidents in dark vigils. Could it also explain the mystery of the 'hand in the dark' experience at a physical mediumship seance?

Attention misperception

Another problem that our brain has in constructing the 'picture in your head' is in paying attention. Change blindness is a hot topic in neuroscience at the moment. We seem to only have a limited amount of 'attention' and we only notice so much change, missing any more that happens. For instance, people do not usually notice gradual changes in scenes, even if they are big alterations. We also frequently miss changes if we are distracted while the change is happening.

Unfortunately, change blindness can leave us open to not noticing vital clues to natural causes for apparent paranormal phenomena. If an unstable stack of objects was gradually slipping, over several seconds or minutes, we might not notice the change until it finally falls over. We might conclude that the stack had looked perfectly stable until it fell over, because we didn't notice it shifting to an unstable position. We might conclude that the 'object movement' was paranormal when it is not.

Paradoxically, we can often have a 'gut feeling' that something has changed in a scene we are observing, even though we can't say what it is. This is mindsight. The interesting point is that, according to research, this can happen both if there is a genuine change in the scene and also if there is not! This could give someone experiencing it the impression that they have perceived something when they have not - a brief sight of a ghost perhaps! This may explain ghost sightings where only one person in a group 'sees' the ghost while others don't, even when they are looking in the same direction.

Xenonormal

Misperception is probably behind many xenonormal experiences. When faced with something unfamiliar or novel, our brains have to decide what it is before passing it to the 'picture in our head'. An unfamiliar object is an ambiguous stimulus by definition since we have no memory of it. This is when our brains may plunder our long term memory to find ANY match, whether fact or fiction. A mysterious light in the sky may match something seen in a film about UFOs. Though the light is actually just Venus, our brains may add 'details', like a saucer shape, to make it appear more like an alien space craft. By putting images of imaginary alien craft into the public domain, we are encouraging people, very occasionally to actually 'see' them when faced with the unfamiliar, the xenonormal.

Misperceptions like those outlined above, coupled with memory limitations, may account for some of the problems we see with witness testimony.

Misperception triggers

Though misperception has been studied quite extensively in the laboratory, it is not so well documented in the field. Perhaps this is a gap that paranormal researchers could fill! The following examples of visual misperception 'triggers' are anecdotal, so it should not be taken as a definitive or exhaustive list.

• quick glances - objects are often misinterpreted when only seen briefly**
• poor viewing conditions - low light, bright light, highly coloured light, fog, etc can all produce misperception
• corner of the eye phenomena - poor resolution on the edge of the visual field produces misperception
• distant objects - these can be the subject of visual substitution
• ambiguous shapes - simulacra, optical illusions, etc.
• partial views of an object (eg shape obscured) - if the shape is partly obscured an object may be misinterpreted
• rapid head turning - may cause apparent movement in the new scene even when everything is stationary
• fast moving objects - may 'vanish' if they do not move as predicted
• unfamiliar object/situation - something completely unrecognised by the observer OR a familiar object in an unexpected situation
• familiar object - something has really changed in a familiar scene but you still 'see' what you expect to see
• line of sight - it is difficult to judge the distance between two objects in the same line of sight

There are, no doubt, other conditions were when objects are misperceived and, sometimes, substituted. Paranormal investigators should try to assess if any of these conditions applied to reported anomalous phenomena sightings.

Many of the conditions listed above are either temporary or rely on very specific viewing conditions that can change quickly (eg. after a quick glance you may stare at an object for longer). When the conditions for the misperception change, the illusion will generally disappear. Such 'disappearances' are, of course, a feature of many ghost sightings.

Attempts by the original witness to reproduce misperception at the same spot usually fail. This would tend to indicate that 'surprise' is also a factor in such experiences. If you are prepared to experience a particular misperception it probably won't happen! However, being aware that misperceptions can happen may make you more likely to experience them, in general.

Whenever our brains do not immediately recognise an object, they will take any clue to come to an answer, right or wrong, before we become conscious of the result. These 'clues' may be other things in the visual field or even what we happened to be thinking about at the time.

We might be more vulnerable to misperception if we are in 'default network' state. This is the state when we are not concentrating on anything in particular, perhaps daydreaming. The state is believed to be the brain's way of reviewing short term memories to decide which to keep and which to discard. This could possibly inform the imagery of misperceptions. During daydreams our minds not only consider the past but possible futures and even wild imaginings. Another possible state conducive to misperception might be boredom (where certain brain areas may become disconnected), due to repetitive tasks for instance. In any of these states, little attention is being paid to surroundings, increasing the possibility of misperception.

** There may be a very specific explanation for 'glance' type misperception (see here).

When do we misperceive?

The conditions for misperception are around us for much of the time. An object may be too distant to see well or it might be dark and difficult to recognise. And all the time things in our peripheral vision are never observed well. So misperception is probably going on most of the time for everyone. So why don't we notice it? Because our brains are the things producing the misperceptions and they are 'validating' them - ie. telling us what we are seeing is real nearly all the time ('seeing is believing').

So the real question is, why do we, very rarely, notice a misperception and interpret it as a strange experience (maybe paranormal)? Misperception hides from us because it usually takes the form of things that are expected. But occasionally our brains get it wrong! We may see a poorly-seen tree as a person but if that 'person' could not possibly have appeared in a particular location without being seen earlier, we notice it! It is like a continuity error in a movie. It seems that our brains can make any particular static scene make sense in itself but not necessarily maintain the illusion of reality correctly for an extended period of time. Quite simply, we can create a version of reality in our heads but sometimes we make mistakes and that's when we notice them.

This suggests a strong link with paranormal reports! If we notice a 'mistake in reality', that is practically a definition of paranormal! If you glance at a human figure in your peripheral vision and, when you turn to look straight at it, it vanishes, the first thing you think is - ghost! This would explain why many (most?) misperceptions that we notice are interpreted as paranormal.

Duration of misperception experiences

In most cases of misperception, the effect is short-lived, generally measured in seconds. This is because the witness gets a better view of the object being misperceived and the illusion is broken. However, there are cases where the misperception can be prolonged because viewing conditions do not improve. It is just such cases that probably produce paranormal reports, as do 'glance' type experiences which rely on their short duration to work.

Multiple sense misperception

Sometimes two senses may interact to produce, or reinforce, a misperception in either, both (or even neither). So, if you see a vague shadow shape in your peripheral vision, while hearing a groaning noise (made by the wind in a tree, maybe), you may get a strong misperception of a hunan figure. The groaning noise, even though it is caused by the wind, may be misattributed to the shadow. This sort of experience may give rise to the idea of an 'interactive ghost' - it might appear to be talking to the witness. This is also based on anecdotal experience and needs formal research.

Forms that misperception takes

As with 'misperception triggers' above, this area has not been researched much. This is another gap that paranormal researchers could fill. The following is based primarily on anecdotal evidence. The following list is extremely unlikely to be exhaustive:

• figures (sometimes only partial) and faces (eg. a 'ghost') (notes 1,5)
• things feared (eg. a watching 'person', a 'shadow ghost', unexplained movement)
• UFOs (note 2)
• things that used to be there (note 3)
• things hoped for (note 4)
• things expected (note 6)

Notes on misperception forms :

1: There is a specific area of the brain (the right middle fusiform gyrus) apparently dedicated to facial recognition - other objects are recognised by other areas. It is, perhaps, unsurprising then that sometimes objects are misperceived as faces. People are also prone to 'over-recognising' human figures for social and survival purposes - you need to know if there is a person present and if they are a possible threat or maybe a friend. The ghost connection probably arises if the figure vanishes on closer inspection.

2: The word UFO is, of course, widely taken to mean 'alien spacecraft' in popular culture. This probably explains why unidentified flying objects are typically interpreted as 'flying saucers'.

3: When we misperceive, objects are substituted from visual memory. While these can be fictional objects (from films, TV programmes, etc) they can also be real. It is therefore not surprising if we 'see' things as present that were once there but have been removed. We might glimpse a once treasured possession in half light when it has been thrown away. This, also, feeds into the idea of ghosts as 'recordings'.

4: When naturalists particularly want to see a species they've never encountered before, they can sometimes 'turn' a similar but more common animal into it (when not seen well!). They are convinced they've seen what they desperately wanted to see even though it is not so. This no doubt happens in other circumstances when people particularly hope to see something (or even someone) not actually physically present!

5: Rarely, some people report ghosts as being only partially visible, eg. the top or bottom half of a human figure or just a limb. This could arise if the misperceived object most closely resembles only part of a body.

6: We may expect to see things in particular situations from similar experiences in the past. This could include fictional situations, so you might expect to see a ghost in a spooky house if you've seen something similar in a movie. If we see a 'figure' where we expect to see one, like at the wheel of a car, it can make a particularly powerful impression (sometimes repeatedly).

Anecdotally, misperception generally takes the form of 'generalised' objects rather than specific examples from memory. So, you may misperceive a human figure, even seeing their clothes, facial features, etc but without recognising them as anyone you've ever seen. This may the result of archetypes.

Misperceived objects

An object can be misperceived as anything of similar dimensions, shape and colour. This generally puts a limit on what the misperception can be (a small rectangular box is never likely to be seen as a human figure but a tall bush might). The worse the viewing conditions, however, the looser such restrictions on size and colour and so on. There could be multiple objects involved as well. They may line up, from a particular angle, to give the impression of a completely different object.

Something that is misperceived doesn't even have to be a physical object. Anything that can create patterns of light will do, such as shadows or highly illuminated surfaces. A pattern of shadows on a wall could resemble a human figure, depending on its shape and size. You could even misperceive a shape caused by a gap between other objects (a hole, in effect)! Reflections can also cause misperceptions. Shadows can also act as 'extensions' to real objects to give the impression of something else.

In low light situations there are often fewer colours visible than normal. This is because there might not be enough light around for normal colour vision or, if using outdoors artificial lighting, the colour range may be restricted by the source. Similarly, if the lighting is from a low sun the range of colours may be limited to the colours of the sunrise or sunset.

This loss of colour vision means visible details of objects are lost. Different coloured areas of an object, that were clearly differentiated in good light, may merge to appear as one colour. The result is that objects can appear radically different, even seeming to change shape or apparently merge with adjacent objects. If there are long dark shadows about, as there will be with a low sun, this can add to an object's changed appearance by rendering some features invisible (in the shadow). Essentially, objects can look quite different in low light, perhaps even suggesting a human figure or face, in a way that would not happen in good lighting.

Anecdotal evidence suggests that such low light situations, with fewer colours than usual and long shadows, may be the cause of many misperception (and paranormal) reports.

Moving objects, when poorly seen, can sometimes give the impression of being alive. For instance, a tree branch blowing in the wind, seen in peripheral vision, might suggest an animal or even a moving human figure.

Archetypes and functional models

Our brains hold models of the objects in the world, derived from our experience. So we recognise a table, even if it is a design we've never seen before. We have an archetypical table in our brains - the essential 'tableness' quality of every table we've ever seen. We also know how tables behave - they are solid and generally they don't move! We have a 'functional model' of how such an object behaves and interacts with other objects.

When we fail to recognise something, for whatever reason, our brains may substitute the real object in our vision with something from visual memory. Rather than something specific (eg. a particular table), experience suggests that it is a generalised form (any old table) - probably the archetype we hold in our brains! Thus misperceptions will typically features recognisable tables, people, clouds, etc but not specific ones we've seen before.* In addition, a 'functional model' will exist for that archetype.

Such 'archetypes' and 'functional models' need not be derived from real experience. We 'know' what a flying saucer looks like from the movies, even if we've never actually seen a 'real' one. So, if you've never seen Venus before and don't recognise it, your brain may add portholes and a saucer shape to make it look like a classic flying saucer. It may even appear to move, because that's what flying saucers do!

Alternatively, since the object we're seeing has not been recognised correctly, it may look and behave differently from the archetype and functional model that our brains have assigned to it. This may give us the impression of strange behaviour and appearance - a spooky appearance! This can lead to reports of objects 'defying the laws of physics'. For instance, we are not used to seeing ornaments flying through the air, so if such a thing happens in a poltergeist case, our brains may become confused, causing it to appear to hang in the air before falling. The apparent 'hovering' occurs while our brains realise that it really is a falling ornament! Many apparently paranormal experiences may be caused by a difference between what our brains expect an object to look and behave like and what it really does.

* Some ghosts ARE people we already know - crisis apparitions - but most are unknown 'people' and are rarely, if ever, positively identified with a particular person.

Effects of misperception

As a result of investigation, we know that most reported paranormal experiences have mundane causes. Further, it is generally thought that misperception is the biggest cause of such reports. Therefore, we should be able to see the effects of misperception (its 'signature') in many paranormal reports. Here are some examples of aspects of paranormal reports that may fall into this category:

• the closer you look for the paranormal, the more elusive it becomes - this has been widely noted, particularly on vigils and among primary witnesses - it can be explained by the fact that the more attention you pay to a misperceived phenomenon, the less likely it is to be misperceived
• children are often said to report more paranormal phenomena than adults - this might be because they are less resistant to the idea of the existence of the paranormal as they are routinely, and uncritically, exposed to stories that include it (see culture) - also young children are unfamiliar with more things than adults and so may misperceive more

Both of these effects are essentially anecdotal, and so would benefit from rigorous studies.

See a ghost for yourself!

Once you become aware of misperception, it is likely you will start to notice mysterious objects, glanced briefly or seen in the 'corner of your eye', that vanish when you look at them properly. You might one day be aware of a 'figure' in the distance or just glanced briefly. On closer examination it may turn into a tree, a plant or some other object that vaguely resembles a human. The 'figure' will appear to vanish, just as ghost frequently do. That's because your brain inserted the 'figure' into the 'picture in your head' instead of the tree which it couldn't see properly. This may well be precisely how many ghost sightings happen. Just keep a lookout in your peripheral vision and, from time to time, you will see ghosts! But don't go looking for specific misperceptions as this appears to inhibit the effect! Just expect to be surprised!

But why do misperceptions often feature human figures and ghosts, rather than more mundane objects? This probably arises from the way our brains work.

Despite probably being responsible for most paranormal reports, misperception is under-researched. You can help! Please send us your experiences by completing the misperception survey.

It is very difficult to reproduce misperception because of the many variables involved that need to be just right. Here is an attempt that might, or might not, work for you.

Eliminating misperception

Since misperception is probably responsible for most paranormal reports, eliminating it during investigations is important. Some ideas for doing that are here.

© Maurice Townsend 2010