Think you see with your eyes? Guess again — your eyes are pretty dumb as such things go, most of the work of vision is done by your brain. But since there’s a lot going on in your world at any time, your brain has to be selective about just what it pays attention to. As a result of this selection process, some pretty simple (and apparently obvious) things can get missed — leading to phenomena like change blindness:
In change blindness, your brain will miss even major changes in your surroundings if they happen to coincide with eye movement (possibly a neurological approach to deal with the fact that everything in your field of vision is “changing” when your eyes move), or even other visual disturbances like static on a video display.