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!