The People Who See Music

The story

Ask a friend a curious question: what colour is the letter A?

Most people will wrinkle their nose and say, letters do not have colours, they are just black marks on the page. But about one person in a hundred will answer instantly, as if it were obvious. A is red, they might say. B is blue, and Tuesday is green, and the number five is yellow, and it has always been that way.

They are not joking, and they are not pretending. They have something scientists call synesthesia, which means, roughly, senses joined together. Every brain is full of parts that share information. In a brain with synesthesia, some kinds of information are joined up in an unusual, automatic way, as if there were extra doorways between rooms, and scientists are still working out exactly how it happens. What it feels like is this: when a sensation or a familiar idea, a letter, a weekday, shows up, an extra sensation tags along automatically. Someone hears a trumpet, and a splash of gold appears in their mind. Someone reads the word cat, and the letters shimmer with their own private colours. Some people even taste shapes, or see the months of the year arranged in a ring around them, like fairy-lights only they can see.

For a long time, people who had it kept quiet, because others laughed or did not believe them. Then scientists began to test it properly, and the tests kept agreeing: this is real. Ask a person with coloured letters to name the colour of every letter, then surprise them with the same test years later, and their answers match astonishingly well. Matching that closely, year after year, is powerful evidence, especially alongside the other careful tests. Brain scanners add their bit too: some synesthetes' brains respond measurably differently, though the patterns vary from person to person.

Scientists have also learned that synesthesia often runs in families, the way curly hair does, and that it is not an illness. For most people it causes no trouble, though it can occasionally be distracting. Many people who have it say it is a gift: their colours help them remember names, spell tricky words, and learn music. Quite a few painters and musicians have described their mixed-up senses as an extra ingredient in their art, painting the sounds they see.

And for the rest of us, synesthesia opens a door to one of the biggest ideas a person can think. You cannot climb inside someone else's head. The world you experience is your brain's own painting of it, and every brain paints a little differently. Most differences are small. Synesthesia is a difference big enough to prove the point: the same song, in the very same room, can be pure sound for you, while the child beside you hears it AND watches an inner light-show of colours, and BOTH of you are telling the truth.

So ask people your curious questions, and listen carefully to the answers, especially the surprising ones. Every mind you meet is a slightly different world, and the only way to visit is to ask.