Amazing what the eye and brain does.

[Fallout]

Originally Posted by myfirstsv

Just see the ceiling. Maybe it doesnt't work if you've necked a few pints of Stella...

Yeah, you need to be able to focus on the red dot.

[embee]

I've been watching the re-runs of the Royal Institution Christmas lectures this last couple of nights, all about the workings of the brain.

Intersting stuff about vision, for example try looking in a mirror reasonably close up, look at your left eye, then look at your right eye. Your eyes appear not to move at all, but of course they do. Your brain shuts off your vision during the move.
Also when you blink the brain "switches off" the vision bit during the blink otherwise it would cause confusion. The example shown was a picture of a street scene in which a series of small details changed in sequence. When the details simply changed you spot them immediately, when a "blink" (a black frame) is inserted in between you don't notice the changes.
Fascinating, the brain always tries to make sense of the signals as best it can, even if it means making stuff up.