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.

WHAT IS SYNESTHESIA, EXACTLY?

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.

HOW DOES IT HAPPEN, AND WHY?

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.

WHO HAS IT?

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.

WHAT’S SYNESTHESIA LIKE?

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.