uncanny valley hypothesis

The uncanny valley hypothesis suggests that as robots or animated characters become more human-like in appearance and behavior, people tend to feel more comfortable up to a point. When they nearly resemble humans but still have subtle, unnatural features or movements, they can evoke feelings of eeriness or discomfort. This dip in comfort is the "valley." However, if the object becomes indistinguishable from a real human, feelings of familiarity and ease usually return. Essentially, the more human-like something is, the more our subconscious reacts emotionally, often with unease when it's almost, but not quite, convincingly human.