Thursday, 1 November 2012

What flipping adverts tell us about ghosts!

It's a bit like having an extra sense! Since I've started noticing misperception, I am getting an insight into how my brain is handling sensory input. For instance, today I noticed a billboard with an advert on it. At first it contained an unlikely, slightly grotesque image before quickly flipping to a more prosaic scene. Adverts are a common source of this misperception 'flipping', where I see one image and then it flips to another, in an instant. There is no fade to grey or shapes rearranging themselves. One second it is one picture, the next a quite different one, like those optical illusions that constantly flip between different versions (such as the Necker Cube). With misperceptions, unlike optical illusions, the picture never flips back.

This raises the question - why are advertising billboards a common source of misperception? I think it's because, you never know what's going to be in a new advert. By contrast most things you see in everyday life are familiar; houses, cars, roads, trees, people, grass, clouds, etc. With familiar objects our brains can easily produce a suitable visual substitution from memory. Would you really notice if one leaf on a tree was exactly as seen by your eyes while another one, less well seen, was a memory substitute? But when faced with a novel image, the brain has a trickier job and sometimes gets caught out changing images.

Here's another question - why didn't I see adverts 'flip' before I discovered misperception? I'm sure my brain still got it wrong, occasionally, for a second or two, so why didn't I notice it? The key word is 'notice' here. We walk down streets every day noticing very little of what is actually going on all around us. Unless, like me, you become interested in natural history, you probably won't notice the street pigeons or foxes. So I never noticed flipping misperceptions until recently because I wasn't interested in the subject. We lavish most of our limited attention on what really interests us.

Next question - why do people who see misperception ghosts notice them? Perhaps it is triggered by a belief in ghosts. Or maybe they noticed a misperception so bizarre they couldn't ignore it. Or perhaps it is simply genetic variability! People who notice such misperceptions may well consider themselves psychic. However it happens, I think some ghost witnesses may see the 'substitute' image for much longer than people like me. What evidence do I have for that? Two words - ghost photographs!

I see many anomalous photos that the photographer says contains a face, figure or other object that I cannot, despite extensive examination, see! As I've speculated before, I think this is a form of permanent misperception. One viewer always sees a ghostly figure while another never does. A crucial point about a photo is that it never changes over time. If one person saw a tree stump as a ghost and someone standing next to them couldn't see it, you could put it down to a different viewing angle. If the second person moved to the same spot as the original witness and could still see no figure, you might put it down to changes in lighting over time. But with a photo, these factors don't apply. Everyone sees exactly the same photo but different people see different things in it. I suspect that someone who sees a ghostly figure in a photo may also see one with their naked eye that is really a tree stump. And for an extended period of time!

It is fascinating to see how human perception actually works. We have an illusion that normal sensory perception is a faithful representation of the physical world around us. Instead, it is more like watching an edited movie where we what we see can depend on what we know.

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