There’s an interesting article by Carrie Gouskos over at Gamespot about the “uncanny valley”, a term borrowed from a 1970 article by Japanese roboticist Masahiro Mori, in the magazine Energy (Japan’s robot-enthusiasm goes back quite a ways).
Mori measured the positivity of people’s responses to being exposed to robots with differing levels of human visual and behavioral resemblance. This degree of comfort with a human likeness is referred to as “familiarity”. What Mori noted is that as an automaton becomes more human-like, the level of familiarity rises, as you would expect.
However, at some point, before reaching near-perfect human approximation, there is a place where it goes from “cute representation” to “soulless and unsettling mockery of humanity”, causing the level of familiarity to bottom out, before rising back up again. This was represented as a steep valley in Mori’s graph, the area where a something has an eerily close (ie uncanny) resemblance to humans, hence the “uncanny valley”.