Thursday, 17 April 2014

Do short-sighted people see ghosts?

Fuizzy shadowI've found a way to avoid noticing misperception - I just take my glasses off. That's despite the fact that everything, apart from stuff really close, goes fuzzy.

Regular readers will be aware that I have, for several years, noticed misperceptions having not done so before. I see ghosts from time to time, for instance, having never seen any at all until I started noticing misperceptions. Everyone misperceives all the time. Much of what you see in peripheral vision, for instance, is made up by your brain. But because we see what we expect to see, few people ever notice this aspect of visual perception.

Misperception happens when your brain cannot see something clearly enough to positively identify it. Your brain then makes a guess at what is there and does a substitution from visual memory. So, if most of what is visible is fuzzy, as it is when I don't wear my glasses, I should be misperceiving just about everything. Except I don't. Why not?

Though everything is fuzzy without glasses, I can still see most objects well enough - I never bump into things. I assume that misperception IS taking place as normal except that my brain is substituting in things I cannot see well with fuzzy objects! If so, does that mean that I need to store fuzzy versions of everything in visual memory in addition to sharp ones? If so, it might explain why my memory is not great. Or does my brain remember all objects in focus, given that I wear my glasses most of the time, and then 'fuzzies' them when required? I've no idea. That would be an interesting research project for someone.

But here's the most interesting point. I've never seen the door ghost (see here) when not wearing glasses. And I am often in the correct position to see the ghost without wearing glasses. So what's going on?

Well, the door ghost is a reflection seen in peripheral vision, so it's a very poorly seen object even when I'm wearing glasses. But without my glasses, the door ghost is even more poorly seen, just a vague fuzzy shape. And I guess a vague fuzzy shape, whether the real thing or a visual substitute, just doesn't resemble a shadowy figure. So no ghost!

Indeed, I never seem to notice misperceptions of any kind when I'm not wearing my glasses. The extra fuzziness may be enough to render the effect unnoticeable. It would be interesting to know if other short sighted people see ghosts when they're not wearing glasses or contact lenses. I suspect not, at least those ghosts are caused by misperception.

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