The letter E is purple

My synesthesia made me feel like a freak. But if my son has inherited this neurological quirk, I hope he realizes what a gift it is.

By Alison Buckholtz

Read more: Science, Neurology, Brains, Life

Jan. 15, 2008 | It was a warm summer afternoon in our corner of the Pacific Northwest, and as I pushed my 4-year-old in the swing, we debated the color of the sun pulsing down on us. Is it yellow or gold, he wanted to know, or is it white, and if it is, why are the spots in front of your eyes pink if you stare at it too long?

"That's a lot of colors," I said, only half attentive to the conversation. "What other colors do you see?"

He thought for a second, as if deciding whether or not to tell me something. Then he said, "The letter E is purple."

In that moment my whole world contracted. I knew exactly what "The letter E is purple" meant. Because, for me, numbers have always had their own color -- not just the number itself (though that, too), but the very character of the number, its presence in the world, is a color. An obvious, intrinsic color. Five, for example, is orange. Two is yellow. Seven is green. It is as natural and unchangeable as the color of someone's skin.

Speaking of skin, people had colors, too. Not everyone. But many people did, whether I liked them or not, whether I knew them well or not. I didn't have to think about it; it was just so. As apparent to me as their eye color.

"The letter E is purple" meant that my son may have synesthesia. I've had it all my life, though I only found out a few years ago that it has a name, and that others have it, too.

Synesthesia is a neurological phenomenon in which activation of one sensory processing system (e.g., numbers or written language) leads to the automatic engagement of a second, distinct sensory processing system (e.g., color) to create a "crossed" sensory perception. For example, as in my case, numbers appear to have their own colors. Or, in other forms of synesthesia, sensory processing is "crossed" with emotion processing, imbuing letters, words, days of the week or months with their own personalities.

There have been many hypotheses about the cause of synesthesia since it was first studied with any rigor in the late 1800s, and a recent article in Nature Neuroscience posits that it is caused by an increased connectivity between relevant brain regions. Put another way, connections that have, over time, been "pruned" in others remain in place for synesthetes, though the reason for this is unknown.

Though there's no one else in my immediate family with synesthesia, except for possibly my son, studies suggest a genetic basis; women and left-handers also tend to have it more. Other than being a possible distraction, synesthesia doesn't interfere with daily functioning and isn't considered a disorder -- synesthetes perform normally on standard neurological exams.

But that's where the certainties end. Estimates of prevalence are variable and shaky, from 1 in 200 to 1 in 100,000, though that same study in Nature Neuroscience suggests 2 in 100 people may have grapheme-color synesthesia, the version that causes my numbers to come alive. "Synesthesia is 'abnormal' only in being statistically rare," according to the abstract from a scientific article in the journal Psyche. "It is, in fact, a normal brain process that is prematurely displayed to consciousness in a minority of individuals."

"Minority" is the operative word here. In fact, the problem with statistics on synesthesia is that many people who have it don't report what they're seeing. The Victorian scientist Francis Galton, cousin of Charles Darwin, writes about this with great feeling in his charmingly titled article "The Visions of Sane Persons" (1881). As Galton and later generations of psychologists have emphasized, sometimes synesthetes who have grown up seeing colors don't even realize that what they're seeing is far from the norm. That's how it was for me. For years I never realized what I saw was different, and so I didn't mention my colors to anyone, including my parents.

There was no reason to, anyway. For much of my childhood, I enjoyed my synesthesia, playing with it as a kitten would bat around a ball of yarn. I'd mentally run through my numbers, one through 10, as if flipping through a paint deck that always landed on my favorite colors. I'd turn my eyes to a teacher halfway through class to bask in her lavender glow. I'd allow her color to soothe me for a few moments, then turn back to the assignment at hand.

As a teenager, it became apparent to me that what I was doing wasn't quite normal. I wasn't quite normal, either. No one else ever mentioned a lavender teacher. I'd heard about auras -- radiant light surrounding a person, somehow revealing or reflecting his or her soul -- and I figured the color I saw from certain people, or numbers, was an aura. Had I somehow gained access to a spiritual dimension?

But the only people I knew who believed in such things were hippies, New Age goofballs and other types who were decidedly marginal in my high-achieving Washington, D.C., suburb. There was no scientific basis, as far as I knew, for what was going on in my head. And in my family, as well as the families of my friends (whose parents worked at the National Institutes of Health, as my father did), science was practically a religion.

Next page: Slowly, I began to close myself off from the barrage of perceptions