The Uncanny Valley

The uncanny valley is a concept in human psychology, where as something begins to look more and more human, we become more comfortable with it. It reaches a certain point at which it looks a little too close to human, but not human enough. That's things like you'll get a little uncomfortable if you see a mannequin in the mall at night. Just that it's almost there, but it doesn't quite fit. And so you start to get that prickly sense. Your fight or flight response might go off.