I’m sure at some point in your life – even if only as a teenager under the influence – you’ve asked yourself this deep, philosophical question:

How do I know that what I’m experiencing is real?

The answer? You can’t. What you see as reality is unique to you, because it’s a complex interaction between the physical world, your senses and your brain.

As proof, here’s a little snippet from my reality:

It’s Tuesday. We’re on the top part of this week’s circle, heading counterclockwise in the direction of Wednesday. We’ve come out of Monday’s black zone successfully, and because Tuesday is red, I’m pretty energized. It’s February, which is my favorite color (green), so all is well. We’re heading clockwise towards March, which is mauve and located at roughy 8 o’clock on the circle of 2012. I think a bit more about the word I described in my last post, plebiscite, and realize that because of the p and b, it’s a very blue word. Could that have been why I didn’t associate it with approval, which is much more yellow-orange, despite the double p?

What?

Until not too long ago, I assumed everyone else saw all the days of the week and months in color, moving around in circles. Letters and numbers, too, each have a unique color. When I think of a word, I see it in my mind’s eye, typed out. Lowercase. I guess that’s why I’m a good speller and why I’ve never understood how people can misspell words. Numbers, on the other hand, march vertically, ever upwards, one after the other, as if they’re trying to reach the moon.

One day I was telling Marc about how eight was such a great number because it’s green, and he gave me a blank, uncomprehending look.

Huh?  he said, realizing he had married an alien. What are you talking about?

I was shocked. He didn’t see letters and numbers in color? No, and in fact, he’d never even imagined it. And the months? Days of the week? Words? He laughed! What a trip! You’re kidding, right?

Turns out I am synaesthetic.  Synaesthesia, a kind of sensory cross-talk, is experienced by about 1 in 100 people. David Eagleman describes it in “Incognito”:

Experiencing the days of the week in color is the most common manifestation of synaesthesia, followed by colored letters and numbers. Other varieties include tasted words, colored hearing, number lines perceived as 3D forms, and letters and numerals experienced as having gender and personalities.”

Like me, most synaesthetes just assume that everyone else experiences reality the way they do. Synaesthesia has been in the news a bit lately, in the New York Times and the Los Angeles Times. One of my favorite blogs, brainpickings, put up a post on it recently, with a link to a film, “an eyeful of sound.” The author Nabokov was synaesthetic; here’s an excerpt from his autobiography Speak, Memory:

The long a of the English alphabet… 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 white… Passing on to the blue group, there is steely x, thundercloud z and huckleberry h. 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.”

The PLOS blog post where I found that snippet also mentions the work of multimedia artist Perry Hall, who, while recovering from a bout of lyme disease, decided to unleash his synaesthesia on the world. He created an iPhone/iPad app called sonified. It takes the luminance and color values from the video camera and uses them to trigger music clips specifically composed for those combinations.

Synaesthesia is a reminder that our idea of objective reality is just that – an idea. Everything we see, do, touch, feel, hear, or sense in any way is mediated by our brains.  And because, unlike computers, we’re not hard-wired at birth, no two brains are identical – not even the brains of identical twins. Our wiring, outlined by genetics, is more finely shaped by experience. So no two realities can ever truly coincide.  And, by extension, no one can claim to know how things “really are.” Eagleman, again:

Think of [synaesthesia] like neighboring countries with porous borders on the brain’s map. And this cross talk results from tiny genetic changes that pass down family lineages. Think about that: microscopic changes in brain wiring can lead to different realities.”

The fascinating thing about synaesthesia is that no two synaesthetes experience this cross-talk in the same way. I might see eight as green, but another person sees it as purple. I might hear a Bach fugue as a blue-green sparkly thing, and another person might see a red-orange shimmer. As far as I know, no one has figured out where these cross-connections originate. Why is eight green? Why is the letter G brown? Why does the taste of chicken make you see yellow? Why not some other color?

Color appears to be deeply rooted in the human archetype. Red and red tones are associated with warmth and excitement or anger, blue with cold and calm. Color psychology is a vast area of study.  Red supposedly stimulates the appetite, but if you put your food on a dark brown, blue or black plate, you’ll eat less. For me and my kind, words, days, numbers and months have a layer of warmth or cold on them, a sense of buzz or a patina of calm. I can’t imagine it any other way.

I just had an epiphany, right here on this very blog: Maybe that’s why I like jelly bellies so much!

Are you synaesthetic?  I asked Dave this morning. There is a genetic component, after all. No, he replied. After a little prodding, he admitted to seeing some numbers and letters in color, and the year as a circle. Like most synaesthetes, he just thought this was normal.

Do you see letters, numbers, words, days of the week or months in color? Do you have other kinds of sensory cross-overs? Do you see a symphony? Taste a color? See months as shapes with a specific location in space? Did you ever think that no one else sees reality in just the same way you do? Leave a comment and share your version of reality.