Nabokov was very curious about his synesthesia and wrote about it in some of his books. For example:
…In the green group, there are alder-leaf f, the unripe apple of p, and pistachio t. Dull green, combined somehow with violet, is the best I can do for w. The yellows comprise various e’s and i’s, creamy d, bright-golden y, and u, whose alphabetical value I can express only by “brassy with an olive sheen.” In the brown group, there are the rich rubbery tone of soft g, paler j, and the drab shoelace of h. Finally, among the reds, b has the tone called burnt sienna by painters, m is a fold of pink flannel, and today I have at last perfectly matched v with “Rose Quartz” in Maerz and Paul’s Dictionary of Color. (From Speak, Memory: An Autobiography Revisited, 1966)
He also pointed out that both his parents were synesthetes and seemed intrigued that his father saw K as yellow, his mother saw it as red, and he saw it as orange—a blend of the two! It isn’t clear from his writings whether he regarded this blending as a coincidence (which it almost certainly is) or thought of it as a genuine hybridization of synesthesia.
Poets and musicians also seem to enjoy a higher incidence of synesthesia. On his website the psychologist Sean Day provides his translation of a passage from an 1895 German article that quotes the great musician Franz Liszt:
When Liszt first began as Kapellmeister in Weimar (1842), it astonished the orchestra that he said: “O please, gentlemen, a little bluer, if you please! This tone type requires it!” Or: “That is a deep violet, please, depend on it! Not so rose!” First the orchestra believed Liszt just joked;…later they got accustomed to the fact that the great musician seemed to see colors there, where there were only tones.
The French poet and synesthete Arthur Rimbaud wrote the poem, “Vowels,” which begins:
A black, E white, I red, U green, O blue: vowels,
I shall tell, one day, of your mysterious origins:
A, black velvety jacket of brilliant flies
which buzz around cruel smells,…
According to one recent survey, as many as a third of all poets, novelists, and artists claim to have had synesthetic experiences of one sort or another, though a more conservative estimate would be one in six. But is this simply because artists have vivid imaginations and are more apt to express themselves in metaphorical language? Or maybe they are just less inhibited about admitting having had such experiences? Or are they simply claiming to be synesthetes because it is “sexy” for an artist to be a synesthete? If the incidence is genuinely higher, why?
One thing that poets and novelists have in common is that they are especially good at using metaphor. (“It is the East, and Juliet is the sun!”) It’s as if their brains are better set up than the rest of ours to forge links between seemingly unrelated domains—like the sun and a beautiful young woman. When you hear “Juliet is the sun,” you don’t say, “Oh, does that mean she is an enormous, glowing ball of fire?” If asked to explain the metaphor, you instead say things like, “She is warm like the sun, nurturing like the sun, radiant like the sun, dispels darkness like the sun.” Your brain instantly finds the right links highlighting the most salient and beautiful aspects of Juliet. In other words, just as synesthesia involves making arbitrary links between seemingly unrelated perceptual entities like colors and numbers, metaphor involves making nonarbitrary links between seemingly unrelated conceptual realms. Perhaps this isn’t just a coincidence.
The key to this puzzle is the observation that at least some high-level concepts are anchored, as we have seen, in specific brain regions. If you think about it, there is nothing more abstract than a number. Warren McCulloch, a founder of the cybernetics movement in the mid-twentieth century, once asked the rhetorical question, “What is a number that Man may know it? And what is Man that he may know number?” Yet there it is, number, neatly packaged in the small, tidy confines of the angular gyrus. When it is damaged, the patient can no longer do simple arithmetic.
Brain damage can make a person lose the ability to name tools but not fruits and vegetables, or only fruits and not tools, or only fruits but not vegetables. All of these concepts are stored close to one other in the upper parts of the temporal lobes, but clearly they are sufficiently separated so that a small stroke can knock out one but leave the others intact. You might be tempted to think of fruits and tools as perceptions rather than concepts, but in fact two tools—say, a hammer and saw—can be visually as dissimilar from each other as they are from a banana; what unites them is a semantic understanding about their purpose and use.
If ideas and concepts exist in the form of brain maps, perhaps we have the answer to our question about metaphor and creativity. If a mutation were to cause excess connections (or alternatively, to permit excess cross-leakage) between different brain areas, then depending on where and how widely in the brain the trait was expressed, it could lead to both synesthesia and a heightened facility for linking seemingly unrelated concepts, words, images, or ideas. Gifted writers and poets may have excess connections between word and language areas. Gifted painters and graphic artists may have excess connections between high-level visual areas. Even a single word like “Juliet” or “sun” can be thought of as the center of a semantic whirlpool, or of a rich swirl of associations. In the brain of a gifted wordsmith, excess connections would mean larger whirlpools and therefore larger regions of overlap and a concomitantly higher propensity toward metaphor. This could explain the higher incidence of synesthesia in creative people in general. These ideas take us back full circle. Instead of saying “Synesthesia is more common among artists because they are being metaphorical,” we should say, “They are better at metaphors because they are synesthetes.”
If you listen to your own conversations, you will be amazed to see how frequently metaphors pop up in ordinary speech. (“Pop up”—see?) Indeed, far from being mere decoration, the use of metaphor and our ability to uncover hidden analogies is the basis of all creative thought. Yet we know almost nothing about why metaphors are so evocative and how they are represented in the brain. Why is “Juliet is the sun” more effective than “Juliet is a warm, radiantly beautiful woman”? Is it simply economy of expression, or is it because the mention of the sun automatically evokes a visceral feeling of warmth and light, making the description more vivid and in some sense real? Maybe metaphors allow you to carry out a sort of virtual reality in the brain. (Bear in mind also that even “warm” and “radiant” are metaphors! Only “beautiful” isn’t.)
There is no simple answer to this question, but we do know that some very specific brain mechanisms—even specific brain regions—might be critical, because the ability to use metaphors can be selectively lost in certain neurological and psychiatric disorders. For instance, in addition to experiencing difficulty using words and numbers, there are hints that people with damage to the left inferior parietal lobule (IPL) often also lose the ability to interpret metaphors and become extremely literal minded. This hasn’t been “nailed down” yet, but the evidence is compelling.
If asked, “What does ‘a stitch in time saves nine’ mean?” a patient with an IPL stroke might say, “It’s good to stitch up a hole in your shirt before it gets too large.” He will completely miss the metaphorical meaning of the proverb even when told explicitly that it is a proverb. This leads me to wonder whether the angular gyrus may have originally evolved for mediating cross-sensory associations and abstractions but then, in humans, was coopted for making all kinds of associations, including metaphorical ones. Metaphors seem paradoxicaclass="underline" On the one hand, a metaphor isn’t literally true, and yet on the other hand a well-turned metaphor seems to strike like lightning, revealing the truth more deeply or directly than a drab, literal statement.