On Flat UI

Design

Flat UI Elements Attract Less Attention and Cause Uncertainty

Summary: Flat interfaces often use weak signifiers. In an eyetracking experiment comparing different kinds of clickability clues, UIs with weak signifiers required more user effort than strong ones.
Sure, and that absolutely makes sense, but these flat UI elements were surrounded by designs that didn't create a particularly great UX either. Still, a very important result.