In 1970, robotics expert Masahiro Mori first described the effect of the "uncanny valley," a concept that has had a massive impact on the field of robotics. The uncanny valley, or UV, effect, describes the positive and negative responses that human beings exhibit when they see human-like objects, specifically robots.
The UV effect theorizes that our empathy towards a robot increases the more it looks and moves like a human. However, at some point, the robot or avatar becomes too lifelike, while still being unfamiliar. This confuses the brain's visual processing systems. As a result, our sentiment about the robot plummets deeply into negative emotional territory.