hunt@spar.UUCP.UUCP (06/22/87)
John Cugini <Cugini@icst-ecf.arpa> writes: > What if there were a few-to-one transformation between the skin-level > sensors ... > My example was to suppose that #1: > a combination of both red and green retinal receptors and #2 a yellow > receptor BOTH generated the same iconic yellow. We humans see the world (to a first order at least) through red, green and blue receptors. We are thus unable to distinguish between light of a yellow frequency, and a mixture of light of red and green frequencies, and we assign to them a single token - yellow. However, if our visual apparatus was equipped with yellow receptors as well, then these two input stimuli would *appear* quite different, as indeed they are. In this case I think that it is highly unlikely that we would have the same symbol to represent the two cases. Consider a species with only two classes of colour receptors, low frequency and high frequency, roughly equivalent to our concepts of red and blue, but with no middle frequency receptors corresponding to a human concept of green). Creatures of such a species when shown pure green light would receive reduced levels from the receptors on each side of green frequency, thus receiving some combination of blue and red signals. This would be indistinguishable from a mixture of blue and red, which we call magenta. Such creatures might then reason (incorrectly) about the possibility of having a middle frequency receptor, and having a many to one mapping between case #1, pure green light, and case #2, a mixture of red and blue, and wonder about how that affects questions of invertibility. As we humans know, if these creatures had such a visual capability, they would invent a new symbol for magenta, and there would be no many to one mapping. > Clearly this iconic representation is non-invertible back out to the > sensory surfaces, but intuitively it seems like it would be grounded > nonetheless - how about it? The fallacy is that iconic representation described is indeed non invertible, but it is also clearly not grounded, since if we had yellow receptors, we would be able to perceive a difference between, and require a new symbol for one of the new colours. Neil/. ----- End Forwarded Message -----