Synesthesia: The People Who See Colors in Letters, and What It Reveals About Personality

For Vladimir Nabokov, the long a of the English alphabet “has for me the tint of weathered wood, but a French a evokes polished ebony.” It was not a writer’s metaphor. It was, quite literally, what he saw.

Nabokov recounted it in his memoir, Speak, Memory, and described it as a family trait: his mother also saw letters in color, as did his son Dmitri. His wife, Véra, saw them in color too, but in colors different from his.

The phenomenon has a name: synesthesia, from the Greek for “sensing together.” And in recent years science has found that it says something interesting, if more modest than is often claimed, about the personality of the people who have it.

What is synesthesia?

Synesthesia is a way of perceiving in which one stimulus automatically triggers a second experience, always the same one.

The best-known variants are:

• Colored letters and numbers: “E” is green, 7 is blue.
• Colored days or months: Tuesday is yellow, March is red.
• Colored sounds or music: a chord looks violet.
• Tasting words, a much rarer variant.

Two features set it apart from imagination or metaphor. It is involuntary: nobody chooses it. And it is stable: the same stimulus produces the same experience for years.

More common than once believed

For decades it was repeated that synesthesia affected one person in 2,000, or even fewer. Those figures had a problem: they were based on people who volunteered to be studied.

In 2006, Julia Simner and her team did something different: they looked for synesthetes in large, unscreened samples. Published in the journal Perception, their study found:

• At least one of the variants studied in 4.4% of 500 students, about 1 in 23.
• Letter-color synesthesia in around 1-1.4%, a figure later confirmed in samples of almost 4,000 people.
• As the most frequent variant, colored days of the week, not letters.

Another myth fell along the way: the idea that it was far more common in women. In large random samples no clear bias appears; the difference came from women being more likely to volunteer.

The test that cannot be faked

How do you tell a synesthete apart from someone with a good imagination or a good memory? The key is consistency.

In 1987, Simon Baron-Cohen studied a 76-year-old painter who saw colors in words. He asked her to describe the color of 103 words. Ten weeks later, without warning her there would be a second test, he repeated the list:

• She matched in 100% of cases.
• A person without synesthesia, with a very good memory and who was told to remember her answers, matched only 17%, and that was after just two weeks.

That logic underpins today’s tests, such as neuroscientist David Eagleman’s Synesthesia Battery, which presents each letter and number several times in random order and measures whether the chosen color is always the same.

The stability can last decades: in one case documented by Simner, a person’s word-taste associations remained almost identical 27 years later. In childhood, by contrast, synesthesia consolidates gradually: in a follow-up of children, the proportion of letters with a fixed color rose from 34% at ages 6-7 to 71% at ages 10-11.

The personality connection: openness to experience

This is where the link with the Big Five model appears. Three independent studies have compared the personalities of synesthetes with those of people without synesthesia:

• Banissy and colleagues (2013), with 81 synesthetes, found higher scores on openness to experience.
• Rouw and Scholte (2016), with a Dutch sample recruited without mentioning synesthesia, also found more openness, along with a greater tendency toward fantasy.
• Chun and Hupé (2016) confirmed more openness, more absorption and somewhat more mental imagery.

Openness to experience is the trait that describes intellectual curiosity, aesthetic sensitivity and a taste for the new. It makes sense that a richer, more cross-wired way of perceiving would go hand in hand with a mind more inclined to explore.

But these data call for a careful reading:

• The differences are small, and the groups overlap a great deal.
• Chun and Hupé, using more systematic recruitment, cautioned that earlier literature may have overestimated them.
• The other traits show no clear pattern: one study found lower agreeableness, another higher neuroticism and lower conscientiousness, and none of those results was replicated.

The most prudent way to put it is that synesthesia is associated with greater openness, not that it causes it, nor that every open person is a little synesthetic.

Do you need vivid imagery to be a synesthete?

Intuition says yes. If synesthesia means “seeing” colors, it ought to go with very vivid visual imagination, the opposite of aphantasia, the condition of people who see no images when they close their eyes.

The evidence is more interesting than that. In 2021, a team including Carla Dance, Julia Simner and Adam Zeman himself, who coined the term aphantasia, analyzed thousands of people and found that people with aphantasia have synesthesia at practically the same rate as everyone else.

The difference lies in where the color is located:

• Some synesthetes are projectors: they see the color out in the world, on the printed letter.
• Others are associators: the color is “in the mind”, or they simply know the letter has that color.

People with both aphantasia and synesthesia were more often associators. In other words, synesthesia does not depend on visual imagery: it can exist even in minds that do not produce images at will.

Genes, wiring and childhood

Synesthesia runs in families, as it did in Nabokov’s. But there is no single “synesthesia gene”: genetic studies point to several genes, different from one family to another, involved in how neurons grow and connect.

In the brain, a 2007 diffusion imaging study found greater structural connectivity in certain regions of people with letter-color synesthesia. A classic hypothesis from Vilayanur Ramachandran and Edward Hubbard proposes that the area that recognizes letters and the one that processes color, which are neighbors in the brain, activate each other more than usual.

Most surprising is the role of learning. A study by Nathan Witthoft, Jonathan Winawer and David Eagleman found that at least 6% of 6,588 synesthetes had exactly the colors of a well-known set of magnetic fridge letters. Among those born before that toy existed, the match was zero.

The conclusion is elegant: the tendency toward synesthesia seems innate, but which color goes with each letter can be learned. It is a good example of neuroplasticity: a biological predisposition that experience finishes painting.

Neither superpower nor disorder

Two ideas circulate widely, and neither fully holds up.

The first is that synesthesia is a disorder. It is not: it is not a psychiatric diagnosis, and research describes it as a developmental variation with no negative effects.

The second is that it turns the people who have it into creative geniuses. There are musicians who describe it, such as Olivier Messiaen, and scientists, such as Richard Feynman, who said he saw the letters in equations in color. But the measured differences in creativity or intelligence are small and overlap heavily with everyone else’s.

Nor is it something that can be trained at will: in a 2014 study, adults who practiced letter-color associations for nine weeks came to describe similar experiences, but most of them faded within three months.

What synesthesia teaches about everyone

Perhaps the most valuable thing about synesthesia is not what it says about those who have it but what it reveals about perception in general: the senses are not sealed compartments but systems in conversation, and in some people that conversation becomes conscious.

It also echoes something the Big Five describes well: personality is not a label but a way of relating to experience. A more open mind does not only seek out more stimuli; perhaps it also perceives them as more intertwined.

If you have ever thought Monday has a particular color, it may be more than a figure of speech. Or it may not. The difference, according to science, is whether that color is still the same ten years from now.

Sources

• Nabokov, V. (1966). Speak, Memory: An Autobiography Revisited. G. P. Putnam’s Sons.
• Baron-Cohen, S., Wyke, M. A. and Binnie, C. (1987). Hearing words and seeing colours: An experimental investigation of a case of synaesthesia. Perception, 16(6), 761-767.
• Simner, J., Mulvenna, C., Sagiv, N., Tsakanikos, E., Witherby, S. A., Fraser, C., Scott, K. and Ward, J. (2006). Synaesthesia: The prevalence of atypical cross-modal experiences. Perception, 35(8), 1024-1033.
• Simner, J. and Logie, R. H. (2007). Synaesthetic consistency spans decades in a lexical-gustatory synaesthete. Neurocase, 13(5-6), 358-365.
• Simner, J. and Bain, A. E. (2013). A longitudinal study of grapheme-color synesthesia in childhood: 6/7 years to 10/11 years. Frontiers in Human Neuroscience, 7.
• Eagleman, D. M., Kagan, A. D., Nelson, S. S., Sagaram, D. and Sarma, A. K. (2007). A standardized test battery for the study of synesthesia. Journal of Neuroscience Methods, 159(1), 139-145.
• Banissy, M. J., Holle, H., Cassell, J., Annett, L., Tsakanikos, E., Walsh, V., Spiller, M. J. and Ward, J. (2013). Personality traits in people with synaesthesia: Do synaesthetes have an atypical personality profile? Personality and Individual Differences, 54(7), 828-831.
• Rouw, R. and Scholte, H. S. (2016). Personality and cognitive profiles of a general synesthetic trait. Neuropsychologia, 88, 35-48.
• Chun, C. A. and Hupé, J.-M. (2016). Are synesthetes exceptional beyond their synesthetic associations? A systematic comparison of creativity, personality, cognition, and mental imagery in synesthetes and controls. British Journal of Psychology, 107(3), 397-418.
• Dance, C. J., Jaquiery, M., Eagleman, D. M., Porteous, D., Zeman, A. and Simner, J. (2021). What is the relationship between aphantasia, synaesthesia and autism? Consciousness and Cognition, 89, 103087.
• Rouw, R. and Scholte, H. S. (2007). Increased structural connectivity in grapheme-color synesthesia. Nature Neuroscience, 10(6), 792-797.
• Ramachandran, V. S. and Hubbard, E. M. (2001). Synaesthesia: A window into perception, thought and language. Journal of Consciousness Studies, 8(12), 3-34.
• Witthoft, N., Winawer, J. and Eagleman, D. M. (2015). Prevalence of learned grapheme-color pairings in a large online sample of synesthetes. PLoS ONE, 10(3), e0118996.
• Bor, D., Rothen, N., Schwartzman, D. J., Clayton, S. and Seth, A. K. (2014). Adults can be trained to acquire synesthetic experiences. Scientific Reports, 4.