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.

Anne Dirkse, Flickr // CC BY-SA 2.0
10 Astonishing Things You Should Know About the Milky Way
Anne Dirkse, Flickr // CC BY-SA 2.0
Anne Dirkse, Flickr // CC BY-SA 2.0

Our little star and the tiny planets that circle it are part of a galaxy called the Milky Way. Its name comes from the Greek galaxias kyklos ("milky circle") and Latin via lactea ("milky road"). Find a remote area in a national park, miles from the nearest street light, and you'll see exactly why the name makes sense and what all the fuss is about. Above is not a sky of black, but a luminous sea of whites, blues, greens, and tans. Here are a few things you might not know about our spiraling home in the universe.


The Milky Way galaxy is about 1,000,000,000,000,000,000 kilometers (about 621,371,000,000,000,000 miles) across. Even traveling at the speed of light, it would still take you well over 100,000 years to go from one end of the galaxy to the other. So it's big. Not quite as big as space itself, which is "vastly, hugely, mind-bogglingly big," as Douglas Adams wrote, but respectably large. And that's just one galaxy. Consider how many galaxies there are in the universe: One recent estimate says 2 trillion.


artist's illustration of the milky way galaxy and its center
An artist's concept of the Milky Way and the supermassive black hole Sagittarius A* at its core.
ESA–C. Carreau

The Milky Way is a barred spiral galaxy composed of an estimated 300 billion stars, along with dust, gas, and celestial phenomena such as nebulae, all of which orbits around a hub of sorts called the Galactic Center, with a supermassive black hole called Sagittarius A* (pronounced "A-star") at its core. The bar refers to the characteristic arrangement of stars at the interior of the galaxy, with interstellar gas essentially being channeled inward to feed an interstellar nursery. There are four spiral arms of the galaxy, with the Sun residing on the inner part of a minor arm called Orion. We're located in the boondocks of the Milky Way, but that is OK. There is definitely life here, but everywhere else is a question mark. For all we know, this might be the galactic Paris.


If you looked at all the spiral galaxies in the local volume of the universe, the Milky Way wouldn't stand out as being much different than any other. "As galaxies go, the Milky Way is pretty ordinary for its type," Steve Majewski, a professor of astronomy at the University of Virginia and the principal investigator on the Apache Point Observatory Galactic Evolution Experiment (APOGEE), tells Mental Floss. "It's got a pretty regular form. It's got its usual complement of star clusters around it. It's got a supermassive black hole in the center, which most galaxies seem to indicate they have. From that point of view, the Milky Way is a pretty run-of-the-mill spiral galaxy."


On the other hand, he tells Mental Floss, spiral galaxies in general tend to be larger than most other types of galaxies. "If you did a census of all the galaxies in the universe, the Milky Way would seem rather unusual because it is very big, our type being one of the biggest kinds of galaxies that there are in the universe." From a human perspective, the most important thing about the Milky Way is that it definitely managed to produce life. If they exist, the creatures in Andromeda, the galaxy next door (see #9), probably feel the same way about their own.


John McSporran, Flickr // CC BY 2.0

We have a very close-up view of the phenomena and forces at work in the Milky Way because we live inside of it, but that internal perspective places astronomers at a disadvantage when it comes to determining a galactic pattern. "We have a nice view of the Andromeda galaxy because we can see the whole thing laid out in front of us," says Majewski. "We don't have that opportunity in the Milky Way."

To figure out its structure, astronomers have to think like band members during a football halftime show. Though spectators in the stands can easily see the letters and shapes being made on the field by the marchers, the band can't see the shapes they are making. Rather, they can only work together in some coordinated way, moving to make these patterns and motions on the field. So it is with telescopes and stars.


Interstellar dust further stymies astronomers. "That dust blocks our light, our view of the more distant parts of the Milky Way," Majewski says. "There are areas of the galaxy that are relatively obscured from view because they are behind huge columns of dust that we can't see through in the optical wavelengths that our eyes work in." To ameliorate this problem, astronomers sometimes work in longer wavelengths such as radio or infrared, which lessen the effects of the dust.


Astronomers can make pretty reasonable estimates of the mass of the galaxy by the amount of light they can see. They can count the galaxy's stars and calculate how much those stars should weigh. They can account for all the dust in the galaxy and all of the gas. And when they tally the mass of everything they can see, they find that it is far short of what is needed to account for the gravity that causes the Milky Way to spin.

In short, our Sun is about two-thirds of the way from the center of the galaxy, and astronomers know that it goes around the galaxy at about 144 miles per second. "If you calculate it based on the amount of matter interior to the orbit of the Sun, how fast we should be going around, the number you should get is around 150 or 160 kilometers [93–99 miles] per second," says Majewski. "Further out, the stars are rotating even faster than they should if you just account for what we call luminous matter. Clearly there is some other substance in the Milky Way exerting a gravitational effect. We call it dark matter."


Dark matter is a big problem in galactic studies. "In the Milky Way, we study it by looking at the orbits of stars and star clusters and satellite galaxies, and then trying to figure out how much mass do we need interior to the orbit of that thing to get it moving at the speed that we can measure," Majewski says. "And so by doing this kind of analysis for objects at different radii across the galaxy, we actually have a fairly good idea of the distribution of the dark matter in the Milky Way—and yet we still have no idea what the dark matter is."


andromeda galaxy
The Andromeda galaxy
ESA/Hubble & NASA

Sometime in the next 4 or 5 billion years, the Milky Way and Andromeda galaxies will smash into each other. The two galaxies are about the same size and have about the same number of stars, but there is no cause for alarm. "Even though there are 300 billion stars in our galaxy and a comparable number, or maybe more, in Andromeda, when they collide together, not a single star is expected to hit another star. The space between stars is that vast," says Majewski.


There are countless spacecraft and telescopes studying the Milky Way. Most famous is the Hubble Space Telescope, while other space telescopes such as Chandra, Spitzer, and Kepler are also returning data to help astronomers unlock the mysteries of our swirling patch of stars. The next landmark telescope in development is NASA's James Webb Space Telescope. It should finally launch in 2019. Meanwhile, such ambitious projects as APOGEE are working out the structure and evolution of our spiral home by doing "galactic archaeology." APOGEE is a survey of the Milky Way using spectroscopy, measuring the chemical compositions of hundreds of thousands of stars across the galaxy in great detail. The properties of stars around us are fossil evidence of their formation, which, when combined with their ages, helps astronomers understand the timeline and evolution of the galaxy we call home. 

What Pop Culture Gets Wrong About Dissociative Identity Disorder

From the characters in Fight Club to Dr. Jekyll and Mr. Hyde, popular culture is filled with "split" personalities. These dramatic figures might be entertaining, but they're rarely (if ever) scientifically accurate, SciShow Psych's Hank Green explains in the channel's latest video. Most representations contribute to a collective misunderstanding of dissociative identity disorder, or DID, which was once known as multiple personality disorder.

Experts often disagree about DID's diagnostic criteria, what causes it, and in some cases, whether it exists at all. Many, however, agree that people with DID don't have multiple figures living inside their heads, all clamoring to take over their body at a moment's notice. Those with DID do have fragmented personalities, which can cause lapses of memory, psychological distress, and impaired daily function, among other side effects.

Learn more about DID (and what the media gets wrong about mental illness) by watching the video below.


More from mental floss studios