Synesthesia: Why Some of Us Can Taste Music and Hear the Rainbow


In recent years, you might’ve heard artists like Pharrell Williams and Kanye West self-identifying as having synesthesia—something that West says has allowed him to make "sonic paintings” and “see sound.”

But just how common is synesthesia? What is it? How does it happen? Due to synesthesia’s relative newness as an area of study, researchers are still working to find answers. 


Synesthesia is a brain condition that may link a person’s senses together in an uncommon manner. For example, sounds might be heard but also seen, or flavors that can be tasted are also visualized. As the inimitable Dr. Oliver Sacks explained to American Public Media in 2009, the effect is “almost as if there's some excessive connection, or abnormal connection between sensory areas which are normally separate.”

Every synesthete’s experience is different, but they generally fall into one of two types: projective or associative. Projective sensory experiences seem to present tangibly—say, a blob of red appears in the room, or the skin grows hot. Associative experiences draw to mind other concepts, moods, or memories.

The possible combinations of senses and stimuli are endless, but the most common types of synesthesia include grapheme-color synesthesia, in which numbers or letters bring about certain colors; chromesthesia, in which sounds (and often music) bring about colors; spatial sequence synesthesia, in which a person’s sense of a number is aligned in their sense of surrounding space; and number form synesthesia, which can bring up a mental map of numbers.


According to research [PDF], synesthesia is a familial trait that can skip generations, and synesthetic experiences are "automatic." Consistencies in this research area suggest there “is some difference between synesthetes and nonsynesthetes," but that difference is still unclear. According to the 2015 research wrap-up "Developing synesthesia: a primer," there’s a widening spectrum of possible causes for it.

For example, the immune hypothesis, first introduced in 2013, suggests that "the interaction between the central nervous system and the immune system during early life may play a pivotal role in the development of synaesthesia." On the other hand, the neonatal hypothesis argues that synesthetic associations "between basic shapes and colors may be present already early in childhood" (formed, say, when you were learning the ABCs on colored blocks as a child while your brain was still developing its sensory pathways), and that "even when these associations can be refined by experience," they can still "interfere with learning novel shape-color associations later."

According to Sean Day, president of the American Synesthesia Association (ASA), that excessive connection might be a result of small but significant anatomical differences in synesthetic brains. Research has recently indicated that fatty nerve insulation called myelin in the brains of synesthetes seems to be more developed along pathways between sensory areas.

Day told NPR, "Because the myelination is different, the interaction between certain parts of the brain is different.” And since this myelin sheath is good for rapid conduction of electronic impulses in neurons, it seems likely that the extra-smooth pathways between sensory areas in a synesthetic brain make for interesting perceptual collaborations between two (or more) of our many senses.


Estimates about how common synesthesia is vary, though current opinion favors the figure of around four percent of the population. Because research into the subject is limited (but increasing) and we lack a catch-all diagnostic test, we don’t know exactly how many of us are experiencing stimuli extraneously, or how common each variety of synesthesia may be.

BBC News points out that the synesthesia roster includes the abstract painter and art theorist Wassily Kandinsky, who communicated “his experience of seeing music in color, line, and form." Vincent Van Gogh and David Hockney are also among the ranks of visual artists who’ve explored the potential realms and representations of their perception in their work (and who, like Kandinsky, weren't shy about vivid colors). Plenty of noteworthy musicians are synesthetes, too, including Tori Amos, Jean Sibelius, Eddie Van Halen, Itzhak Perlman, and Leonard Bernstein.


Whether it’s seeing a patch of mauve hanging in the air during a Metallica encore or simply knowing that the number 12 is green, each synesthete’s special sensory link is different. Pitchfork explains that, in the mind of Duke Ellington, “a D note looked like dark blue burlap [and] a G was light blue satin,” while a young Pharrell Williams saw baby blue and burgundy hues when he first heard the music of Earth, Wind & Fire.

Synesthesia researcher Dr. Carol Crane feels guitar music “[brush] softly against her ankles” and hears trumpets as they “make themselves known on the back of her neck,” she told Monitor on Psychology. Day, the ASA president, who is also a linguistics professor in Taiwan, told the publication that, for him, the taste of steak incites “a rich blue,” while steamed gingered squid “produces a large glob of bright orange foam, about four feet away, directly in front of me."

According to Simon Baron-Cohen, a University of Cambridge synesthesia researcher (and Borat’s real-life cousin), most people with synesthesia are quite content with the way they experience the world. “If you ask synesthetes if they'd wish to be rid of it, they almost always say no," Baron-Cohen told Monitor on Psychology. "For them, it feels like that's what normal experience is like. To have that taken away would make them feel like they were being deprived of one sense."

The benefits of the condition might actually be measurable now, too, according to the results of a preliminary exploration by the British Psychological Association published this year. Seeking out possible correlations between synesthesia and certain personality traits and abilities, the study found that in comparison to non-synesthetic or "control" participants, "synesthetes showed (by decreasing order of estimated effect size) greater absorption, verbal comprehension, visual convergent thinking, openness to experience, originality of verbal divergent thinking, and usage of mental imagery."

For synesthetes, that's music to their eyes.

Women Suffer Worse Migraines Than Men. Now Scientists Think They Know Why

Migraines are one of medicine's most frustrating mysteries, both causes and treatments. Now researchers believe they've solved one part of the puzzle: a protein affected by fluctuating estrogen levels may explain why more women suffer from migraines than men.

Migraines are the third most common illness in the world, affecting more than 1 in 10 people. Some 75 percent of sufferers are women, who also experience them more frequently and more intensely, and don't respond as well to drug treatments as men do.

At this year's Experimental Biology meeting in San Diego, researcher Emily Galloway presented new findings on the connection between the protein NHE1 and the development of migraine headaches. NHE1 regulates the transfer of protons and sodium ions across cell membranes, including the membranes that separate incoming blood flow from the brain.

When NHE1 levels are low or the molecule isn't working as it's supposed to, migraine-level head pain can ensue. And because irregular NHE1 disrupts the flow of protons and sodium ions to the brain, medications like pain killers have trouble crossing the blood-brain barrier as well. This may explain why the condition is so hard to treat.

When the researchers analyzed NHE1 levels in the brains of male and female lab rats, the researchers found them to be four times higher in the males than in the females. Additionally, when estrogen levels were highest in the female specimens, NHE1 levels in the blood vessels of their brains were at their lowest.

Previous research had implicated fluctuating estrogen levels in migraines, but the mechanism behind it has remained elusive. The new finding could change the way migraines are studied and treated in the future, which is especially important considering that most migraine studies have focused on male animal subjects.

"Conducting research on the molecular mechanisms behind migraine is the first step in creating more targeted drugs to treat this condition, for men and women," Galloway said in a press statement. "Knowledge gained from this work could lead to relief for millions of those who suffer from migraines and identify individuals who may have better responses to specific therapies."

The new research is part of a broader effort to build a molecular map of the relationship between sex hormones and NHE1 expression. The next step is testing drugs that regulate these hormones to see how they affect NHE1 levels in the brain.

Vivien Killilea/Getty Images for Caruso Affiliated
A Founder of Earth Day Looks Back on How It Began
Vivien Killilea/Getty Images for Caruso Affiliated
Vivien Killilea/Getty Images for Caruso Affiliated

On the very first Earth Day in 1970, Denis Hayes stood on a stage in Central Park, stunned by the number of people who'd come to honor the planet. Now in his 70s, Hayes remembers it was like looking at the ocean—“you couldn’t see where the sea of people ended.” Crowd estimates reached more than a million people.

For Hayes, who is now board chair of the international Earth Day Network, it was the culmination of a year’s worth of work. As an urban ecology graduate student at Harvard University, he’d volunteered to help organize a small initiative by Wisconsin senator Gaylord Nelson. Nelson was horrified by the 1969 oil spill in Santa Barbara, California, and wanted to raise awareness about environmental issues by holding teaching events similar to those being held by civil rights and anti-war activists.

Senator Nelson saw a growing disconnect between the concept of progress and the idea of American well-being, Hayes tells Mental Floss. “There was a sense that America was prosperous and getting better, but at the same time, the air in the country was similar to the air today in China, Mexico City, or New Delhi," Hayes says. "Rivers were catching on fire. Lakes were unswimmable.”

Nelson's plan for these environmental teach-ins was for speakers to educate college students about environmental issues. But he had no one to organize them. So Hayes, Nelson’s sole volunteer, took control on a national level, organizing teach-ins at Harvard first and then across the U.S. Initially, the response was tepid at best. “Rather rapidly it became clear that this wasn’t a hot issue at colleges and universities in 1969,” Hayes says. “We had a war raging, and civil rights were getting very emotional after the Nixon election.”

Still, both Hayes and Nelson noticed an influx of mail to the senator's office from women with young families worried about the environment. So instead of focusing on colleges, the two decided to take a different tactic, creating events with community-based organizations across the country, Hayes says. They also decided that rather than a series of teach-ins, they'd hold a single, nationwide teach-in on the same day. They called it Earth Day, and set a date: April 22.

Hayes now had a team of young adults working for the cause, and he himself had dropped out of school to tackle it full time. Long before social media, the project began to spread virally. “It just resonated,” he says. Women and smaller environmental-advocacy groups really hooked onto the idea, and word spread by mouth and by information passing between members of the groups.

Courtesy of Denis Hayes

With the cooperation and participation of grassroots groups and volunteers across the country, and a few lawmakers who supported the initiative, Hayes’ efforts culminated in the event on April 22, 1970.

Hayes started the day in Washington, D.C., where he and the staff were based. There was a rally and protest on the National Mall, though by that point Hayes had flown to New York, where Mayor John Lindsay provided a stage in Central Park. Parts of Fifth Avenue were shut down for the events, which included Earth-oriented celebrations, protests, and speeches by celebrities. Some of those attending the event even attacked nearby cars for causing pollution. After the rally, Hayes flew to Chicago for a smaller event.

“We had a sense that it was going to be big, but when the day actually dawned, the crowds were so much bigger than anyone had experienced before,” Hayes said. The event drew grassroots activists working on a variety of issues—Agent Orange, lead paint in poor urban neighborhoods, saving the whales—and fostered a sense of unity among them.

“There were people worrying about these [environmental] issues before Earth Day, but they didn’t think they had anything in common with one another," Hayes says. "We took all those individual strands and wove them together into the fabric of modern environmentalism.”

Hayes and his team spent the summer getting tear-gassed at protests against the American invasion of Cambodia, which President Nixon authorized just six days after Earth Day. But by fall, the team refocused on environmental issues—and elections. They targeted a “dirty dozen” members of Congress up for re-election who had terrible environmental records, and campaigned for candidates who championed environmental causes to run against them. They defeated seven out of 12.

“It was a very poorly funded but high-energy campaign,” Hayes says. “That sent the message to Congress that it wasn’t just a bunch of people out frolicking in the sunshine planting daisies and picking up litter. This actually had political chops.”

The early '70s became a golden age for environmental issues; momentum from the Earth Day movement spawned the creation of the Clean Air Act, the Clean Water Act, the Safe Drinking Water Act, the Endangered Species Act, the Marine Mammal Protection Act, the Environmental Education Act (which was initially passed in 1970 and revived in 1990), and the Environmental Protection Agency.

“We completely changed the framework within which America does business, more than any other period in history with the possible exception of the New Deal,” Hayes says. “But our little revolution was brought entirely from the grassroots up.”

In 1990, Hayes was at it again. He organized the first international Earth Day, with about 200 million participants across more than 140 countries. Since then it’s become a global phenomenon.

Despite its popularity, though, we still have a long way to go, even if the improvements Hayes fought for have made these issues feel more remote. Hayes noted that everything they were fighting in the '70s was something tangible—something you could see, taste, smell, or touch. Climate change can seem much less real—and harder to combat—to the average person who isn’t yet faced with its effects.

Hayes also notes that people have become more skeptical of science. “Historically, that has not been a problem in the United States. But today science is under attack.”

He warns, “This [anti-science sentiment] is something that could impoverish the next 50 generations and create really long-term devastation—that harms not only American health, but also American business, American labor, and American prospects.”


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