In Jackson’s knowledge argument, Mary is a talented color scientist, who was prevented from seeing color since birth. Despite that deprivation, she has studied all there is to know about color processing. When she finally sees something red for the first time, will she learn something new? The argument goes that she probably will, and it means that there is something to having a conscious experience that outstrips representational knowledge, and perhaps also functionalism as a result.
Empirically, we know that sensory deprivation of this kind can severely limit normal brain development. After years of such deprivation, chances are her ability to see color may be permanently gone, or drastically changed somehow. To assume that she can see red exactly like we do is to force our imagination through some plausibly incoherent assumptions.
So instead, why don’t we consider a more realistic example that would serve the same purpose: Maru is a young child who has never tasted natto before. Genetically, she is a supertaster. Like many young children in her culture, she can cook simple meals for herself. She is deeply interested in food and culinary art. But her own parents dislike natto, which is not so uncommon in her culture. So she has never tried it. She heard that it has such a distinctive flavor that either she will love it or hate it. She has been told that natto is basically a kind of fermented soybean. So it is in a way like miso, although the flavor driven by the fementedness is a lot more intense. It is not necessarily as salty, but it is even funkier than old cheese, or Chinese fermented bean curd. In fact, it is on the level of Taiwanese stinky tofu, although for natto the intensity is more on the palette than on the nose. It has a gooey texture, like it is mixed with raw egg white or something. It’s basically ineffable what it is like, she’s been told. She has to try it to find out herself.
The inquisitive and imaginative Maru-chan asks a lot of questions about this curious food. She regularly thinks about what it would taste like. One morning, after a slumber party at her best friend’s, they have natto and rice for breakfast. So she finally gets to try it for the first time. Does she learn anything new?
Obviously, that depends on how Maru-chan’s ‘research’ has gone. But one possibility is, she may say: this is exactly how I always imagined it to be! Based on the other experiences that are familiar to her, with some remarkable level of imagination, she might have actually figured out what it would taste like. On reflection, hasn’t that also happened to us sometimes, for other stimuli? Experiencing something for the first time doesn’t always feel so surprising. So it is possible that she will learn nothing fundamentally new. Tasting natto just confirms what she already knows without first-hand conscious experience. In that case, conscious experiences don’t necessarily outstrip representational knowledge.
Alternatively, it could be that Maru does learn something significantly new. Natto isn’t quite like what she’s imagined it to be. From here, perhaps she gains the ability to imagine it correctly. She also learns some new self-knowledge: this is what natto tastes like to her. At a subpersonal level, some mechanisms in her brain acquire the new information that this is what the relevant sensory vehicle is like, for natto - it is a bit like the vehicles for this other taste, that other taste, nothing like the vehicles for the tastes of ikura, karaage, etc. This is not the sort of stuff one can learn by reading books. Even if one learns the information as a person, it doesn't mean the relevant mechanisms in the brain will get it too.
So in either case there’s no challenge to functionalism.
P.S. This story is inspired by my experience of once dining with an ardent anti-functionalist in a Japanese restaurant in downtown Manhattan. I tried to convince the adventurous philosopher not to order the natto dish, but I failed.