Novelist Vladimir Nabokov was a synaesthete. The letter "c" is light blue, "a" evokes a sense of "weathered wood," and "r" feels like "a sooty rag being ripped," he wrote. At a young age he associated the number five with the colour red.
You don’t need cross-wiring in the brain to have a feel for this kind of sensory overlap. Common metaphors depend on the same idea: a loud tie, a sharp cheese, feeling blue. But it’s intriguing to think that some people are experiencing a world that is more richly textured – perhaps seeing reality in greater wonder, drawing connections that for the rest of us are unusual and enchanting. Here’s a (translated) poem by another famous synaesthete, French poet Arthur Rimbaud, on vowels:
A Black, E white, I red, U green, O blue: vowels,
I shall tell, one day, of your mysterious origins:
A, black velvety jacket of brilliant flies
Which buzz around cruel smells,
Gulfs of shadow; E, whiteness of vapours and of tents,
Lances of proud glaciers, kings, shivers of cow-parsley;
I, purples, spat blood, smile of beautiful lips
In anger or in the raptures of penitence;
U, waves, divine shudderings of viridian seas,
The peace of pastures dotted with animals, the peace of the furrows
Which alchemy prints on broad studious foreheads;
O, sublime Trumpet full of strange piercing sounds,
Silences crossed by Worlds and by Angels:
O the Omega, the violet ray of Her Eyes!