By early October, the summer tourists have left Martha’s Vineyard. Marcia Smilack, camera in hand, walks slowly along a barren dock, waiting for something in her peripheral vision to evoke the sound of a cello in her ears or the feel of satin on her skin. When it does, she stops, points her camera at the water, and waits to hear or feel it again. Then she shoots her picture.
Smilack belongs to the group of one to four percent of people worldwide with synesthesia, the neurological mixing of the senses. No two synesthetes have exactly the same perceptual experiences. Many perceive each number, letter of the alphabet, or day of the week as a different color. For others, sounds from the environment are always accompanied by moving geometric patterns in their “mind’s eye.”
Smilack has a rare form of synesthesia that involves all of her senses—the sound of one female voice looks like a thin, bending sheet of metal, and the sight of a certain fishing shack gives her a brief taste of Neapolitan ice cream—but her artistic leanings are shared by many other synesthetes. Scientists estimate that synesthesia is about seven times more common in poets, novelists, and artists than in the rest of the population. (Some of the most famous examples include artists David Hockney and Wassily Kandinsky and writer Vladimir Nabokov.)
In the last decade, this connection between synesthesia and art has drawn much attention from neuroscientists. And now several genetic and behavioral studies aim to pin down the biological mechanisms linking art and synesthesia, with hopes of answering even bigger questions about how every brain perceives art.
“Until seven or eight years ago, it was still a long-standing question whether the things these people were saying, this synesthesia, was real or bogus,” said Vilayanur Ramachandran, a neuroscientist at the University of California, San Diego.
But in 1999, Ramachandran and his colleagues began giving tests to synesthetes that showed they weren’t making up their sensory experiences. In one test, a computer showed the image of a square with a few black ‘2’s scattered within a block of black ‘5’s. Researchers then asked the subjects what shape the ‘2’s made. For most people, Ramachandran said, this task may be impossible, and those who can complete it take several minutes. But for synesthetes who see a ‘2’ as a different color from a ‘5,’ it was simple: 90 percent identified the correct shape, and most did it in just a few seconds.
Subsequent experiments by Ramachandran and others using brain scanners also confirmed that synesthesia is a genuine sensory experience.
Ramachandran says that since the areas of the brain that are activated by color are adjacent to those activated by number, synesthesia might be a result of some kind of “cross wiring” in the brain.
“When we’re born, the brain has all kinds of connections, and these gradually get pruned,” Ramachandran said. “So synesthesia might be a mutation of this pruning gene, or set of genes, so that adjacent areas don’t get separated.”
Since synesthesia runs in families, most scientists agree it must have a strong genetic component. For the last two years, neuroscientist David Eagleman of the Baylor College of Medicine has been collecting DNA from large families of synesthetes and analyzing it for “hot spots”—groups of about 100 genes that are distinct from non-synesthetes.
Eagleman’s first round of analysis, which he intends to publish in the next couple of months, includes samples from about 150 synesthetes and identifies one promising hot spot on chromosome 16.
Now that he’s identified a hot spot, Eagleman says the next step is to sequence that particular region in both synesthetes and non-synesthetes to find one or more “synesthetic” genes.
Eagleman says his studies are unique in the genetics field. “All of the other studies ask how genes correspond to physical attributes, like hair color or height,” he said. “This is the first example of something I’m calling perceptual genomics: how genes correspond to how people actually see the world.”
Smilack says her vision of the world is simply an unfiltered version of most people’s perceptions, not a blaring cacophony of sensation. “To most people, my experience sounds like it would be too much information, all at once,” she said. “But really there’s just a harmony of everything. The key word is layers—layers of perception. There’s never just one, but they’re never all in your face.”
Recently, Smilack tried to recreate one of her visual-auditory sensations for non-synesthetes. The idea came to her when she was looking through some photographs she had taken in Venice while listening to music by Maurice Ravel in the background.
“All of a sudden an adagio came on,” she recalled, “and the music looked exactly as the pictures sounded. I was having it in both directions at the same time. So I thought, I wonder if I could do this on purpose.”
The result was a video she made called “Ravel in Pink.” Smilack says she knows it produces a powerful perceptual experience in non-synesthetes because “I used it in a lecture once, and when I looked out in the audience, I could see people crying.”
Neuroscientist Jamie Ward of University College London has long recognized people’s strong emotional ties to “visual music”—music accompanied by any visual element—and recently performed experiments that probe the phenomenon’s connection to synesthesia.
“It’s a very popular art form, visual music,” he said. “You’ll see at pop concerts now flashing lights, and accompanying light shows, pyrotechnics. So we wanted to find out why this is so appealing.”
Ward first recruited six synesthetes who “saw” images when they listened to music. He asked them to draw the images that appeared to them when they heard specific notes from cellos and violins. For a control group, he asked non-synesthetes to do the same. Ward then made animated movies showing these drawings paired with the music that elicited them, and showed the movies to 200 random individuals visiting the London Science Museum. “One sound and two images would be displayed side by side,” he said, “and they just had to click on the image that was most ‘right’ for the sound.”
About 70 percent of the time, the participants picked the synesthetes’ drawings over the non-synesthetes’ as better fits, Ward reported at the British Association for the Advancement of Science Festival earlier this fall. Ward says this shows that in some way, all of our brains must be wired to recognize the connections that synesthetes actually “see.”
“It probably reflects a basic property of the brain,” he said. “Information enters from the eyes, or ears, or septum, but once it’s in there, our neurons connect in ways that are not random.”
To find out more about the neurological mechanisms involved in synesthetic experiences, Ward plans to do brain scans of synesthetes while they hear music.
Another aspect of this research, Ward added, is “what it can tell us about how we appreciate art, and why certain art forms are appealing. We’re starting to use principles of neuroscience to understand what artists have been doing for centuries.”
Ramachandran agrees, saying, “Ward’s work shows that the phenomenon of synesthesia can be used as a bridge between two cultures: science and art. It’s the Holy Grail, what everyone is looking for.”
Smilack, too, sees an inextricable connection between synesthesia and art of all cultures.
“In our art there is something universal. If someone asked me ‘What is art?’ I would say art is patterns. In the same way that DNA is a pattern that could explain an entire species, there are patterns in nature that show up in my dreams and show up in my art. And maybe none of us are consciously aware of them.”
Originally published December 13, 2006