Recent developments in neuroscience indicate that we 'see' with our brains rather than our eyes. Though our eyes contribute to the 'picture in our heads', there is also input from our memory. In particular, objects in our vision can sometimes be 'substituted' with similar things from visual memory. These 'visual substitutions' may be responsible for some ghost, UFO and other anomalous sightings.

The point of this page is not to discuss the theory (for a full discussion of how visual substitutions work, see misperception) but to consider the practical consequences of this type of misperception for paranormal research. When might such substitutions take place and how might investigators recognise them, both from witness reports and personal experience? This is a relatively new idea, so some of what appears here is speculative or based on personal experience rather than systematic research.

Likely circumstances of visual substitutions

We do not go round seeing things that are not there all the time! Visual substitutions are rare, like optical illusions. Once you are aware of the possibility that they can happen, you may well start to notice them from time to time in your daily life. You might see something odd in the 'corner of your eye', only for it to 'vanish' or 'change' into something else when you look at it directly.

Visual substitutions are most likely in poor viewing conditions. These include:

• low light or high light
• objects in the distance
• thick dust, fog, heavy rain, snow or similar atmospheric phenomenon
• objects glanced briefly
• objects out of focus (eg. not wearing prescription glasses or contact lenses)
• objects in peripheral vision

In addition, objects that are unfamiliar or unexpected, if not seen well, might cause misperception. Generally, objects seen well in good viewing conditions are unlikely to be misperceived. It is interesting to note that many anomalous phenomena are reported in poor viewing conditions.

Form of visual substitution

Objects are substituted with something similar from memory. So, what form do these substitutions take? It is likely that expectation or suggestion play a significant role in the form of visual substitutions.

There has to be something to be misperceived, such as a shadow, patch of light or physical object. This will form a template on which the substitution will be based. It will limit to possible visual substitution by its shape, size and features. A misperceived object must at least vaguely resemble a human figure for it to be replaced by a clear image of a person from memory. This means that two people misperceiving the same object may agree, in broad outline, on what they both saw. On the other hand, one may not misperceive at all and disagree profoundly.*

The circumstances of a misperception can, through expectation or suggestion, affect the form of a substitution. So a 'ghost' might be seen in spooky surroundings. A light in the sky on a lonely road, by contrast, may appear as an extra-terrestrial craft recalling, as it does, many science fiction film scenarios. Prior knowledge of a site, such as a building's reputation for being haunted, might heavily influence the form of visual substitutions. It is also possible that someone's psychological state, in particular any strong fears or desires, at the time of a sighting may influence the substitution.

Here is a witness example of expectation affecting an 'object' seen in peripheral vision:

"Recently, I was eating at an outside table of a restaurant on the pavement. It was getting dark but still light enough to see everything around perfectly. Suddenly, something caught my attention under the table. It was a black and white pigeon walking between my feet! I was surprised! Though I'd seen pigeons and sparrows around the tables, picking up dropped crumbs, I hadn't seen a bird bold enough to walk between someone's feet! So, I looked under the table to see where the bird had gone but there was nothing there!

Puzzled, I decided to investigate my sighting. The first thing that struck me was that, in the gathering gloom, there were no birds about, though there had been many earlier. Presumably, they had decided it was time to roost. This didn't rule out a real bird, of course, but it made it less likely. However, I then noticed that my feet were only a couple of centimetres apart - far too small a gap to allow a bird as big as a pigeon to get through. It was, by now, obvious that I had not seen a pigeon at all.

So, I watched my feet directly for a while and then saw 'it' again. OK, I didn't see a pigeon but I did see a pattern of light moving swiftly. It gave the impression of an object passing between my feet. It was caused by passing car headlights! But why a pigeon? Expectation explains it - having seen pigeons moving around between the tables earlier, my mind obviously just decided it was one of them. What surprised me was how vividly I 'saw' the ghostly pigeon. It seemed utterly real at the time, even though it was only glimpsed briefly. It reminded me of the many times I'd heard ghost witnesses say that what they'd seen was completely solid and real. I was shocked at how vivid a misperception could be! "

Detecting visual substitutions

In the example above, the reporter is puzzled by the disappearance of the 'pigeon' and investigates further. In many cases, it is unlikely that witnesses, often surprised or even shocked, will behave in this way. So how can investigators determine if a visual substitution is a likely explanation for a sighting?

You need to include some specific topics when interviewing witnesses to pick up relevant details. Thus, it is important to find out:

• the viewing conditions (see list above, also the duration of sighting)
• how detailed the description of the anomaly is
• whether anything else was seen in the same area immediately before or after the sighting
• the exact time, date and position of both witness AND anomaly as well as weather
• how much the witness knew of any reputation the site may have

A combination of a highly detailed description of the anomaly coupled with poor viewing conditions could indicate a visual substitution. It is unlikely that a really detailed view can be had in poor viewing conditions. Any objects seen in the area just before, or after, the sighting might be the object being misperceived, particularly if there is a vague resemblance in shape.

Reproducing substitutions

The information about time, position and weather gathered earlier are vital. With this information it might be possible to reproduce the sighting on site. It might be necessary to change the time of day, when out of doors, to get correct lighting conditions. For instance, the fact that a sighting was 30 mins before sunset is more important than that it was 6pm in the evening. The weather can affect lighting conditions as well, particularly bright sunshine or thick cloud. Misperceptions are highly sensitive to viewing and lighting conditions. If the original witness can be present, that might be useful in case they see the possible misperception again.

More info on substitutions

Visual substitutions are distinct from hallucinations in that (a) they require an external visual stimulus and (b) they are part of normal brain perception. Hallucinations, by contrast, require no external stimulus and generally happen when brains are not working normally, eg. due to certain illnesses, disorders or drugs. Some hallucinations, like sleep paralysis, occur when the brain is working normally but require no external stimulus.

If 'substitutions' come from the witness's memory, why don't people report recognising 'ghosts' as people they already know? Sometimes they do - in the case of crisis apparitions and doppelgangers, for instance. In other cases of visual 'substitution', the actual figure 'seen' is probably influenced strongly by the shape of the object being misperceived. Our brains are always trying to make sense of what we see using all the sources of information available. It may simply make no sense to see someone you know in an unlikely situation.

Visual 'substitutions' might explain why so many supposed extra-terrestrials seen in UFO cases are humanoid in appearance. Scientists studying astrobiology (the study of extra-terrestrial life) say it is extremely unlikely that extra-terrestrial life would have evolved on other planets in a similar way to ours. So extra-terrestrials are most unlikely to look human.

* in the case of multiply witnessed phenomena, there is often a discussion between the witnesses that may lead to a 'single' description even if they saw different things

© Maurice Townsend 2008