system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does it look like the eyes of a painting are following you but not the eyes of a statue?
gpt
A painting is two dimensional, usually when this effect is observed the eyes are painted in a way which depicts the irises as circles, which your brain interprets as eyes fixated on you. When a three dimensional eye, real or on a statue, is observed from different angles the iris' shape changes from the point of view of the observer, your brain has evolved to accurately determine where a set of eyes is pointing based on their geometry relative to you. 

TLDR: Flat 2D eyes confuse your brain as the irises are perfect circles, which usually means they are facing you. 3D eyes don't confuse your brain.