Uncanny Valley

The Uncanny Valley is a principle of robotics concerning the emotional response of humans to robots and other non-human entities. It was theorized by Japanese roboticist Masahiro Mori in the late 1970s through psychological experiments in which he measured human response to robots of varying degrees of anthropomorphism. This principle states that as a robot is made more humanlike in its appearance and motion the emotional response from a human being to robot will become increasingly positive and empathetic, until a point is reached at which the response suddenly becomes strongly repulsive.

Thenceforth, as the appearance and motion are made to be indistinguishable to that of human being, the emotional response becomes positive once more and approaches human-human empathy levels.

This gap of repulsive response aroused by a robot with appearance and motion between a "barely-human" and "fully human" entity is called the Uncanny Valley. The name harkens to the notion that a robot which is "almost human" will seem overly "strange" to a human being and thus will fail to evoke the requisite empathetic response required for productive human-robot interaction. Mori separately tested responses to variations in the movement and appearance of the robot from completely machinely to almost human. For both variables, the chart displayed a similar curve as depicted in the illustration. (Via Wikipedia)