the screen isn't moving but the observable portion is. This change causes you to try to refocus but you know you're watching a movie on a 2D plane where you don

the screen isn't moving but the observable portion is. This change causes you to try to refocus but you know you're watching a movie on a 2D plane where you don't control the depth of field, so you let the change "guide" your attention on the screen. It's something some people are more used to than others. I don't like it and I feel like it pulls me out of a scene. Looking around in a well done 3D movie feels more natural because my eyes DO change where they converge which is a better approximation of real life when compared to 2D where none of that happens. Ultimately your brain adapts to what you expose to it the most.