Mori's hypothesis states that as a robot is made more humanlike in its appearance and motion, the emotional response from a human being to the robot will become increasingly positive and empathic, until a point is reached beyond which the response quickly becomes that of strong repulsion. However, as the appearance and motion continue to become more distinguishable from a human being, the emotional response becomes positive once more and approaches human-to-human empathy levels.
This area 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 captures the idea that a robot which is "almost human" will seem overly "strange" to a human being and thus will fail to evoke the empathic response required for productive human-robot interaction.
And here's a graph showing the hypothesized emotional response of human subjects plotted against the anthropomorphism of a robot. The uncanny valley is the region of negative emotional reponse to robots that are "almost human. " (You can click on the graph for a clearer image.)
The Polar Express (with Tom Hanks, pictured above) and, as Mori hypothesized, I did find the "almost human" CGI animation in that film to be a little creepy. The idea here is that the uncanny valley seems like a strange anomaly-- that is, it seems like we should feel greater affection and empathy for non-human simulations as they more closely approximate "real" human appearance and movement, but at some point (the uncanny valley), our empathetic reponse to them drops off dramatically and we become revulsed by the imitation. But why is this the case?
I can imagine several possible explanations, all of which are problematic in their own way, but my first intuition is to say that there is a fundamental "reality/appearance" distinction here that we are deeply invested, cognitively, in preserving. The one thing the chart above is missing, I think, is an indicator of what that line is and where it is crossed. What seems obvious to me is that there should be a "NON-HUMAN/HUMAN" divider, like the one I have added here. (See amended graph.)
This way, we can understand how the uncanny valley has its "upward" curve. Without it, there would simply have to be a radical "break" between the simulation and the real human being, with no gradual upwards approximation back toward the real. The non-human/human divide must intersect at the point of the human corpse, I think, which is the point at which whatever revulsion we feel at the "simulation" of the human-- my hypothesis is that this revulsion is motivated by our aversion to "deception"-- begins to be replaced by an affectively similar, but categorically different, kind of revulsion, i.e., the kind of revulsion that is motivated by our aversion to morbidity and mortality. So, the most real and life-like human simulation will provoke almost the exact same response as a corpse, and they will both be coincidentally located at the bottom of the valley of the uncanny.
BUT... when I tried floating my hypothesis to a few of my colleagues over dinner last night, Professor Grady pointed out to me that I may not have accomplished as much with this explanation as I had hoped. Inserting the non-human/human (appearance/reality) axis certainly DOES explain how the uncanny valley can be charted as a "valley"-- and not simply a precipice-- but it still presumes that both the image (or simulation of the real) and "the real" itself exist on some kind of a continuum. Yet, as close as our affective reactions to an "almost real" human simulation and a real human corpse may be, there is nonetheless a radical categorical break between how we think about the two.
Now, Professor Grady spends a lot more time thinking about "the image" than I do-- though I might arguably spend more time thinking about "the human" than he does-- so pairing up our noggins on this one made for a very interesting and productive conversation. (Prof. Grady used to keep a blog himself, to which I would love to direct you in order to get the other side of this conversation, but alas it is no more. Contact me if you want to sign the petition to have him reinstate it! In the meantime, though, you're stuck with me.) The more I think about the uncanny valley, the more questions it opens up for me concerning the "image" of the human being and our investments in it qua "image"... but this post is already gone on a bit long.
Up next: what does this have to do with the metaphysics of "race"?