Traversing the uncanny valley
It was in the late 1970s that Masahiro Mori first observed what was later termed the uncanny valley. Through his work in robotics he noted that the human emotional response to his machinations would become more positive as they became more human in appearance and mannerism. This general upward trend in positive emotional response would continue until the robot achieved a level of near human realism, at which point the human reaction would drop off to the point of revulsion. The human reaction would remain in this uncanny valley and would only rise again once there was no discernable difference between the robot and a living, breathing human being.