Metaphorical thinking is the wellspring of the human imagination — that virtuosic cognitive pivot of describing what a thing is through something it is not. “Everything which distinguishes man from the animals depends upon this ability to volatilize perceptual metaphors in a schema, and thus to dissolve an image into a concept,” Nietzsche proclaimed in his meditation on metaphor and reality.

Some of our mightiest metaphors draw on color to describe our perceptual and psychoemotional reality — a blue mood, a red rage. But while for most of us these metaphorical pairings of concepts are a form of abstract thinking encoded in symbolic language, some people experience a literal transliteration of the senses — for them, a particular number or letter or music note or day of the week may indeed be blue or red, rendered in unmistakable color in their mind’s eye.

Synesthesia is a neurological crossing of the senses, in which a stimulus in one sense (say, sight) evokes a sensorial response in another (say, smell), so that the synesthete registers a particular smell as inherently endowed with a particular color (or a number with a sound, or a tactile texture with a smell). Although synesthesia has long been thought to be an extremely rare condition, a growing body of neurological research and scholarship exploring centuries of written accounts from the world’s body of literature have revealed it to be far more common. Oliver Sacks has written about its science. The writings of Virginia Woolf, Dylan Thomas, James Joyce, William Faulkner, and Charles Baudelaire reveal them to be among its famous embodiments. But no one has described the interior experience of synesthesia and its transcendent sensorial discombobulation more electrically than Vladimir Nabokov (April 22, 1899–July 2, 1977) in his 1951 autobiography, Speak, Memory (public library).

“The confessions of a synesthete must sound tedious and pretentious to those who are protected from such leakings and drafts by more solid walls than mine are,” Nabokov writes, confessing that he has frequently experienced various mild aural and optical hallucinations since childhood. But as the crowning curio of his unusual sensory apparatus, he holds up his “fine case of colored hearing.” Constructing a kind of private Newtonian rainbow or Moses Harris color wheel of the alphabet, Nabokov writes:

Perhaps “hearing” is not quite accurate, since the color sensation seems to be produced by the very act of my orally forming a given letter while I imagine its outline. The long a of the English alphabet (and it is this alphabet I have in mind farther on unless otherwise stated) has for me the tint of weathered wood, but a French a evokes polished ebony. This black group also includes hard g (vulcanized rubber) and r (a sooty rag being ripped). Oatmeal n, noodle-limp l, and the ivory-backed hand mirror of o take care of the whites. I am puzzled by my French on which I see as the brimming tension-surface of alcohol in a small glass. Passing on to the blue group, there is steely x, thundercloud z, and huckleberry k. Since a subtle interaction exists between sound and shape, I see q as browner than k, while s is not the light blue of c, but a curious mixture of azure and mother-of-pearl. Adjacent tints do not merge, and diphthongs do not have special colors of their own, unless represented by a single character in some other language (thus the fluffy-gray, three-stemmed Russian letter that stands for sh, a letter as old as the rushes of the Nile, influences its English representation)… In the green group, there are alder-leaf f, the unripe apple of p, and pistachio t. Dull green, combined somehow with violet, is the best I can do for w. The yellows comprise various e’s and i’s, creamy d, bright-golden y, and u, whose alphabetical value I can express only by “brassy with an olive sheen.” In the brown group, there are the rich rubbery tone of soft g, paler j, and the drab shoelace of h. Finally, among the reds, b has the tone called burnt sienna by painters, m is a fold of pink flannel, and today I have at last perfectly matched v with “Rose Quartz” in Maerz and Paul’s Dictionary of Color. The word for rainbow, a primary, but decidedly muddy, rainbow, is in my private language the hardly pronounceable: kzspygv.

With an eye to Nabokov’s exquisitely vivid account, Diane Ackerman observes in her splendid Natural History of the Senses that “either writers have been especially graced with synesthesia, or they’ve been keener to describe it,” and adds:

Great artists feel at home in the luminous spill of sensation, to which they add their own complex sensory Niagara. It would certainly have amused Nabokov to imagine himself closer than others to his mammalian ancestors, which he would no doubt have depicted in a fictional hall of mirrors with suave, prankish, Nabokovian finesse.

Complement this particular fragment of the wholly indispensable Speak, Memory with a synesthetic musician’s animation of what it’s like to hear Bach in color, then revisit Nabokov on inspiration, the necessary qualities of a great storyteller, what makes a good reader, and his passionate love letters to Véra (who was also a synesthete).