As I recounted in my first post on the uncanny valley, I learned of this phenomenon from a student in one of my classes. I can't remember the exact context of his bringing it up-- it had something to do with our knowledge of the outside world as contested, and then proven, by Descartes in his Meditations-- but I do remember my student claiming something like that we could never really be totally deceived by a "virtual reality" simulation, because our brains are "hard-wired" to know the difference between reality and its simulation. The uncanny valley "proves" this, he claimed.
Now, I'm almost always suspect of claims about the so-called "hard-wiring" of our minds, but I am especially so when it comes to what seem to me like socially-constructed categories. However, I will admit, of course, that there are some rules and structures that appear to be inviolable in human thinking. The law of noncontradiction, for example. Or the fact that all "experience" is known in space and time. Or that God speaks to humanity through Johnny Cash. (That last one, especially.)
Now, my claim in the original uncanny valley post was that there must be some kind of meaningful and significant dividing line that intersects the bottom of the valley. In the context of the uncanniness of robots and the like, I think that intersecting line distinguishes between the human and the non-human. But I think that line could, and does, represent other major categorical divisions in other contexts, as I suggested in the second installment might be true when we think about race or racial passing. I think we could chart a similar phenomenon with gender and sexuality, too. The more I think about it, the more the "uncanny valley" seems to represent a kind of basic structural phenomenon that is not only iterable but, dare I say it?, hardwired in human thinking. If this is true, then that means that the uncanny valley can't really be about "the human" (or any race, gender, or sex category of "the human"), but rather must be about some other superstructural distinction of which those other distinctions are substructurally derivative.
As I tried to suggest, though incompletely and somewhat unconvincingly in the original post, I think the important distinction being made in any uncanny valley is between the real and the apparent. Or, in different terms, the distinction being made is between that which is "made to appear" and that which "naturally appears." In Greek philosophy, it's the difference between physis (φύσις, that which has a beginning in itself) and techne (τέχνη, that which has a beginning in another). So, the root of the aversion that we feel to the coincidence of the familiar and the unfamiliar is, as I originally claimed, an aversion to deception, to taking the simulation for the real, to conflating the "like" and the "is." Products of techne can be "made" to be very much LIKE physei onta, but we have a deep and abiding (perhaps "hardwired") commitment to maintaining the distinction between the truth and its (even VERY CLOSE) approximation.
Over on his blog, Anotherpanacea has a different take on the uncanny valley (which I highly recommend reading). He focuses on the singularity of the human face and he claims, among other things, that our aversion to things like bad plastic surgery is motivated by the fact that plastic surgery introduces ambiguity into our ready-to-hand taxonomies of facial recognition, thus producing (through techne, I would add) the impression of the familiar in the unfamiliar, and vice versa. He contests my claim that our aversion is at its root an aversion to deception, because he claims that the experience of the uncanny is prejudicative or prereflective.
I'm sticking to my claim, though, because I think in any experience of the uncanny there is at least some kind of minimal reflection or judgment happening. I think I can justify this with the following example: if we were actually deceived by a simulation, that is, if we really took it to BE what it was only LIKE, then we wouldn't have the experience of the unheimliche. We would just have the experience of the "real" (familiar) thing. So, somewhere in the hidden recesses of our consciousness, it seems to me, the experience of the uncanny MUST involve a simultaneous and coincidental experience of two categorically different things (the familiar and the unfamiliar, the real and the simulation, the truth and the approximation). Our aversion to this kind of ambiguity is tanatmount to an aversion to deception. Now, I think AnPan is right that it doesn't quite rise to the level of complex reflection and judgment where one might make the possibile-deception thetic to oneself. However, if we want to explain how something like the uncanny valley can be applied to several different categorical distinctions (which I obviously think it can), then we need some manner of articulating the more fundamental violation of the difference between "being" and "being-like."
So, although I hardly think that things like racial or sexual categories are "hard-wired" into our brains, and I would be willing to allow for the possibility that the human/non-human distinction isn't either, I think the interesting thing about the uncanny valley is that it shows how even in the case of socially-constructed categories our commitment to the reality/simulation difference produces the same kind of cognitive dissonance when it is breached. If we take "whiteness" or "female" or "human" to mean something REAL, whether that "reality" is "true" or not, we find ourselves attracted to the simulation of that reality only up to a certain point, after which we are averse to the danger of mistaking the false and the true, the manufactured and the natural, the "like" and the "is"...
... whatever "it" is or is like.