The graph above charts the valley of human repulsion. Popularly sited examples are regularly found in the fields of robotics and 3D animation. Here's one that illustrates the point pretty well.
In the (mostly) computer animated Pixar movie WALL-E the little robot, the title character, is widely adored. In the narrative the little guy has been alone for hundreds of years, the last remaining robot cleaning up the ecological mess the humans left behind when they abandoned the planet. Over time he has developed a "glitch": sentience and a personality. He is kind, sentimental, a romantic. His kindness and goodness are hugely attractive. Aesthetically speaking, his squat body and ocular headlights - which rise and fall to change his expression - are cute, attractive, likeable. WALL-E's friendly demeanor has an effect on the other robots and humans he meets and he is eventually the impetus that reboots the entire human race to start over on planet Earth. On the graph above WALL-E might be located somewhere along the arc that describes industrial robots and humanoid robots. Likely near the apex.
In contrast, the motion capture animation of Tom Hank's mystical conductor from The Polar Express
was off-putting to many people. In the context of the narrative, and in all fairness, Hank's character was a bit gruff and because of that it took some time to warm up to him. But not even the charming, charismatic everyman acting skills of the five-time Oscar nominee (and two-time winner) could charm movie goers into embracing the awkward, too-human or not human enough digital doppelganger. In other words, the Polar Express plummeted right over the edge of the Uncanny Valley and crashed at the bottom. On the above chart, this depiction stirred a response similar to a corpse inexplicably brought back to life, seemingly unaware of it's own demise. In short, it was kind of creepy and unnerving.
In Scott McCloud's very smart 1993 book, Understanding Comics, He makes an argument that I hope fits into this conversation. I'll try to paraphrase it. As the rendered likeness of a character becomes more photo-realistic, it becomes harder for the reader to imagine herself or himself in the skin of the character. In otherwords, generalized human features represent all humans, but overly detailed representations only represent one specific person.