Monday, 14 July 2014

Ghosts on sunny days

Crows in a treeSomehow I don't expect to see a ghost on a bright sunny day. But why not? When I noticed someone on a familiar local bench recently, I was curious to see who it was. The person was lying down, presumably sun bathing. I certainly wasn't expecting a ghost!

I was a little shocked, once I got a better view, to see that the figure on the bench had vanished, to be replaced by a bunch of brightly coloured plastic bags. So, a ghost then! On a bright sunny summer's day!

It was, clearly, a misperception. The bags were of a size and position where they suggested, to the casual observer, a person lying on the bench. I, as that observer, actually saw them as a very real person, not a mere suggestion. Though I couldn't see a face, I clearly observed bright green shorts and a white top of some kind. Given the position of the 'person,' and some bushes between me and the bench, I wouldn't have seen a face even if there had been one present. And that is what made the misperception work - everything was in the right place and in the right proportions to be a real person. And so a real person is precisely what I saw, albeit one generated by my visual memory.

What continues to amaze me about misperception is how something quite minor, like the chance arrangement of some plastic bags, can produce a big response in the brain of an observer. The bags literally became a recumbent human figure. I saw no bags whatsoever, initially at least. In the past, I could not quite see how someone might mistake a tree stump for a real human figure, complete with clothes and facial features, or spot 'port holes' on what was clearly the planet Venus. Visual substitution provides the mechanism for this apparently astonishing transformation. It seems that our brains like to make sense of what we see so much that they sometimes let us 'see' things that are not physically present, often in surprising detail.

I am no longer surprised by the level of detail in reports that were clearly generated by misperception. It is not a case of faulty memory or exaggeration - the witness really did see exactly what they reported. It's just that what they saw wasn't actually physically present at the time. I now see such misperceptions so frequently that they only occasionally shock me, when I see a really dramatic example, like the bags on the bench. It would be easy to see how someone else who notices misperceptions as I do might consider themselves psychic. And please don't assume that someone who sees port holes on Venus needs an eye test!

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