Tuesday, 20 May 2014

How ghosts vanish!

Ghostly cylinderAs regular readers will be aware, I have a tendency to notice my own misperceptions. Like most people, I was blissfully unaware of them until I learned how visual perception really works. Since understanding that some of what we see is actually placed there by our brains from our own visual memory, I've started to notice this mechanism in action. It can be disconcerting, amusing, occasionally annoying, never dull. A big plus is that I have, as a result, seen several ghosts for the first time in my life.

We all misperceive all the time. Much of what we cannot see well, in peripheral vision or poor lighting conditions for instance, is substituted from visual memory. Most of the time we do not notice this because the brain comes up with good guesses, often entirely correct, as to what the poorly-seen objects really are. Even the incorrect guesses are usually so plausible that most people seldom, if ever, notice these misperceptions.

However, once you staying noticing yourself misperceiving, life can get a bit odd. It is bizarre watching an object suddenly flip from one thing to something else entirely. And that's precisely what I experience from time to time.

It's usually fairly easy to see why my brain got confused. Take the example here (right above), first discussed in an earlier post. I see the picture as a blank page being opened in a magazine, despite the fact I know that's wrong. Others may not see it what I see, that being the nature of misperception.

Ghostly cylinder undoneNow look at the next photo (right), which is the same picture but not so tightly cropped. You can now see the top of the magazine and it is clear that the 'open blank page' is actually part of a completely separate object. You can also see more of this other object - a white card. There are different shadows there, further dispelling the 'open blank page' impression in the previous photo.

This is the sort of thing I see when a misperception 'breaks'. Once I get a better view of the scene, the misperceived object suddenly changes to something else. And if I was seeing a ghostly figure, it vanishes!

In a photograph we can only see a scene in one way. This is why I continue to see the 'open blank page' in the upper photo, despite knowing its true nature. However, in real life the witness can generally get a better view. They can get closer, for instance, or look from a different angle. Or improve the lighting. Or the object itself might move.

Any of these things might 'break' the misperception. It usually occurs instantly - one object is simply replaced by another. It isn't always obvious that one object has visually 'transformed' into another, especially to someone unfamiliar with misperception. Instead, the object first seen by the witness may appear to vanish, leaving only a previously concealed 'background' object suddenly revealed. And this is how ghosts caused by misperception vanish!

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