The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human

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.)