Masahiro Mori’s Uncanny Valley hypothesis states that, as artificial beings get closer to resembling real humans, the slightest errors or inaccuracies can shift our responses from empathy to disbelief and even disgust. It’s why, in Toy Story, we love Woody and Buzz Lightyear, but are totally unmoved by Andy, their human owner.
This is something both videogame and movie special effects artists are having to grapple with now that processing power is allowing ever more naturalistic representations of human characters. And grappling with it they are. —Artists climb the uncanny valley (Guardian)
A good introduction to the subject.