I've been teasing people on here with a "mirror test", but no one seems to bite, so I thought I'd post here instead.
Daniel has mentioned this a few times, but I'm not sure people realise how bizarre and amazing it really is!
Just to illustrate the point, go and look in a mirror, and look at your eyes. As you move your gaze from one eye to another, you might not have noticed before that you can't see your eyes moving as they flick from left to right. All you see is your eyes stationary looking either at the left or the right, but no movement as they flick from one to the other. Why is that?
The answer is because we move our eyes in flicks called saccades, moving from one position quickly to another, pausing briefly, then flicking on to the next. What our eyes are doing is taking a "snapshot" at each pause, and our visual cortex and higher brain then analyse each snapshot.
The amazing thing is that while the eyes are moving between pauses, the brain actually "blanks" the signal, because otherwise what you'd see would be a blur. That's why you can't see your eyes moving in the mirror.
This is a trick that magician's use in "sleight-of-hand" tricks. You literally don't see if you are moving your eyes!
Get someone else to look in the mirror at the same time, and copy you. You can see their eyes moving, and they can see yours, but they won't be able to see their own eyes moving.
So why then do we see a continuous scene when the signal from our eyes is being switched off all the time?
Now it gets freaky! That's because you aren't perceiving what your eyes see, but a model in your brain that your eyes just help inform! That's why dreams, and in particular lucid dreams, can look and feel so like real life, because the same modelling mechanism in your brain is creating what you can sense in a dream, just this time without the eyes painting the picture.
My mind was totally blown by that revelation!
There is more, such as how LITTLE we actually perceive the world, but I'll leave that for a later discussion!
I've even had instances in lucid dreams where there was something about the scene I was looking at that somehow seemed odd or incomplete, and yet I couldn't easily place my finger on what it was. In a way it seemed similar to the effect of looking at objects outside the fovea, except that it was happening even where I was directly looking. I even remember a particularly interesting dream in which I saw something that seemed like it should have been completely geometrically and visually impossible to experience. It makes me suspect that in dreams our minds are frequently taking incomplete, abstract ideas and somehow creating the illusion of a complete, concrete image that in fact might be so riddled with missing or “fuzzy” parts that it could even be self-paradoxical.
That's it. Effectively just "catching" the brain blanking our vision at the start of the saccade.
You mentioned the blind spot. That's related to my comment about how little we see. We only see a few degrees in sharp focus anyway, over the fovea. The rest is all very low resolution, and we do these saccades to our vision is essentially "off" for much of the time, and yet we appear to see a continuous, clear representation. It's a bit like that in dreams, where although we might remember a really vivid scene, actually the brain only has to model the bit we are interested in accurately. The rest is just "assumed".
Hi tev! There's another thing I've noticed that I've not heard people talk about much, and that is when you flick your eyes away from something that is moving you can see it freeze for just a fraction of a second. I found this while driving on a motorway (freeway) next to a lorry. It's wheels were going around, though not too fast, at about 40 mph, and as I flicked my eyes away I could see the whole wheel stationary.
I've noticed it before. It's interesting. I've discovered that I can still see streams of small, bright targets against a dark enough background (such as distant lights) during saccades, but that's about it.
It's also intriguing how well our minds fill in the missing information from the big optic nerve hole in our retinas. It takes some effort to notice this even though it's not located all that far from our central vision!
Anyone tried this?