在「Flat UI Elements Attract Less Attention and Cause Uncertainty」這邊透過追蹤眼球的技術，發表了研究結果：
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.
其中最明顯的一個例子就是大家被訓練「有底線的文字應該可以按」，這也是最能馬上被想到的問題... 不過這算是 Flat UI 的問題嗎？
The popularity of flat design in digital interfaces has coincided with a scarcity of signifiers. Many modern UIs have ripped out the perceptible cues that users rely on to understand what is clickable.