I am a daily PC user. As most users, I have a taskbar (using Windows) that shows icons of programs. My two screens are big (24") and I'm at ~60cm distance from them, so fairly often I need to turn my head. What I notice is.. that if I turn my head, but look with my eyes at the icon taskbar (or even keep looking) one specific icon is moving with the movement of my head. When I turn my head left the letter on the icon moves left too, like this (3x original size):
Other icons don't seem to move (they have no letters).
But in reality – it does not move (too, like the other icons).
I'm using negative glasses (-4.5).
Why does this happen? It doesn't happen when I don't have my glasses on.
Best Answer
I've seen the same effect, and the glasses are the key. Some glasses have a bit of a prismatic effect, slightly shifting different colors by different angles. This can create a pseduo-stereo effect where solid areas of different colors appear to float above or sink below the plane of your screen.
When you move your head, your visual cortex expects to see the apparent positions of non-moving objects in the foreground shift relative to the apparent positions of non-moving objects in the background. But, since the objects aren't actually fore and back, the shift doesn't happen; and your visual cortex interprets the lack of apparent shift as actual motion of the foreground relative to the background...
... or something like that, anyway.