The effect is not only visual...
For all the focus on "realistic-looking" faces, people seem to forget that Masahiro Mori's original thesis regarded not the "look" of robots, but their movements. His argument was that, if we were looking to apply robots to any industry populated by human workers, we must make sure that they move in accordance to the way humans do, lest the workers will feel unease and distrust, which will impair productivity and increase the chance of injury.
His particular points were to do with the way contemporary robots moved too fast, or much too geometrically perfect, or how they jerk when switching directions, with instant acceleration or deceleration -- all qualities devoid in human movements.
Later on, this research was applied to visual appearance as well, since the same uneasiness is experienced when something just looks "too real" yet not quite enough. Sometimes, a human-looking robot looks absolutely real while standing perfectly still, only to break that illusion when it attempts to move in a non-organic way.