The Uncanny Valley
"The way our face naturally looks is an important part of our humanity"
Project Face Design
In aesthetics, the uncanny valley is a hypothesized relationship between the degree of an object's resemblance to a human being and the emotional response to such an object.
The more it resembles a human, the higher the observer’s affinity will be. Untill the point where the humanoid object appears almost, but not exactly, like a real human being. This elicits an uncanny, or strangely familiar, feeling in observers.
When humans enhance their faces too much, the same phenomenon may occur. People around them notice that there is something unnatural/ something strange about their face.