Synesthesia was historically thought to occur in only a few forms. The most common one is “colored hearing,” the coming together of color and musical sound. Thanks, however, to research by scholars in many fields, we now know that colored sound is only one of many types of synesthesia that artists use. Any of the five senses may be involved; they might manifest in any of 54, or more, different forms, from the perception of colored phonemes (colored letters and numbers) to colored taste, to tasting words and music. Some feel music as a texture on their skin. Others  see letters and numbers as little girls or schoolteachers or bushes as animals, or trees as giants. There is even a more recent finding of a type of synesthesia called “mirror-touch,” in which the person displays an extreme capacity for empathy.

We can test living artists for synesthesia by means of visual and aural tests, as well as fMRIs (functional magnetic resonance imaging). But we cannot be certain about those no longer alive.

Among those we know of are physicist Richard Feynman, writer Vladimir Nabokov, composer/performers Duke Ellington and Itzhak Perlman, and visual artists David Hockney, Carol Steen, and Marcia Smilack. It is strongly suspected that Wassily Kandinsky, Charles Burchfield, and Vincent van Gogh also had it. We see many references to it in their writings, as well as manifestations in their art.

Interest in synesthesia peaked around the turn of the 19th century, then after a decline, rose again at the end of the 20th century and the beginning of the 21st. Why now? Why then? What, if anything, do the two eras have in common?

Some artists are suspected of faking their synesthesia. It is possible that Edvard Munch, for instance, may have been faking it. Scriabin may have faked it. In fact, many people around the turn of the 19th century did fake synesthesia. It was so “in” then. In Scriabin’s case, his color/music equivalents uncannily correspond to those of Mme. Blavatsky, whereas genuine synesthetes, have unique color/sound equivalents (or other manifestations). Why would some artists claim to be synesthetic if they aren’t? And why has this trait been considered more desirable during certain historical eras?

I myself became interested in synesthesia as an art historian whose first love was music. I learned through neuroscience that synesthesia was an actual phenomenon, real and demonstrable. I found out that scientists could look into brains of synesthetes and observe simultaneous nerve responses in discrete areas. In my work since, I have proceeded to differentiate between real, genuine, or constitutional synesthesia and metaphorical synesthesia.

To return to the question of why synesthesia discussions and claims peaked during particular times, one theory is that fins-de-siècles have characteristics in common. People during these transitional times are more likely to experiment with drugs, search for alternative lifestyles, etc. But then why wouldn’t synesthesia have blossomed during the 1960s?

Munch may have wanted to be synesthetic because of his theories of unity, series, and cycles. There is no question that “The Scream” and others of his art works evoke sound and sound waves, as did many of Van Gogh’s paintings before him.

Munch’s life and work correspond to a time filled with French, Belgian, Russian, and American symbolist/spiritualist/theosophist reactions to oppressive materialism. During these times, synesthesia became commonly regarded as superior, even genius. In addition, genius and madness became closely associated with each other. Something like synesthesia, that was thought of as the opposite of rational and analytical, could be considered desirable and special during these contradictory times.

A split occurred, driven by hard scientists or rationalists who regarded synesthesia as degenerate or even pathological. The senses were considered the ultimate human order; synesthesia broke down that order, so synesthetes were considered inferior, crazy, or even degenerate.

I have seen how synesthetic artists, when encouraged and supported, can expand, cultivate, and become more conscious of their synesthesia. It is like an attribute one has taken for granted (“doesn’t everybody?”). Artists only vaguely aware of it have found that knowledge strengthens awareness and perception. Indeed, I have heard artists say that their synesthesia and their awareness of it help the flow.

Kendall Briggs, a composer and professor at Juilliard, is a good example of a contemporary musical synesthete. Briggs became conscious of his multi-sensory synesthesia after speaking with me. But, like all synesthetes, he would say he always was synesthetic.

His cello concerto corresponds uncannily to Marcia Smilack’s “Cello Music.”  He felt it when he saw her photograph (and she took the picture upon “hearing” cello music).

But it seems that one must be conscious – that is, not to make it happen, but to be aware of its happening … Smilack would say she is a “fisherman” of images. She watches, listens, and waits for the right one.

The Web makes possible instant communication and sharing between synesthetes This supportive atmosphere makes possible more recognition and nurturing of artists possessing synesthesia.

It is not that different from “normal” eyesight, hearing, pitch, and the like. There are no doubt many individuals walking around with synesthesia or perfect pitch, but if unused, these gifts are meaningless.