If you tell me your phone number is 713-555-8240, I won't need to write it down. Because this is what I will remember:

(As phone numbers go, it's not bad, but I wouldn't wear it.)

Valentine's Day, is not pink and red to me-it is forest green (February) and burnt orange (14).

Beethoven? Mostly sage and gold, that is, if it's in a major key. Dave Mathews, without a doubt, I hear in shades of brown. This little-known idiosyncrasy that enables me to remember my very first credit card number or recall some obscure SAT word (only because it matched my bedspread) is known as synesthesia.

Though we synesthetes are rather normal folks, assures Dr. David Eagleman, a researcher at The University of Texas Medical School at Houston, we have more-than-normal overlap in our sensory wiring. Some of us see numbers or letters in color. Some of us hear music or sounds in color.

Some of us get really cross-wired and can taste sounds, hear odors, or feel the taste of chocolate cake.

And if you ask some synesthetes where the number 17 is in space, they might point to their left and say "over there."

"Synesthesia is a harmless perceptual condition that represents a bleeding over of information between the senses," says Eagleman, a visiting professor in the Department of Neurobiology and Anatomy. "Think of it like neighboring countries with porous borders on the brain's map."

Genetically Flavored

Eagleman is conducting research on us synesthetes for reasons beyond our odd talents.

"External features are easy to distinguish. You can hunt for genes that make someone brown-eyed or blue-eyed, tall or short. But it turns out there's just as much variation in people's internal worlds. Everyone perceives the world in subtly different ways. We wanted to know if there was a way to go after the genes for the internal differences."

Like the proverbial apple, our colorful traits may not fall far from the family tree. "It was first noted in 1880 that synesthesia tends to cluster in families, but no one has done the genetic analysis.  We're looking for participants who have synesthesia running in their family trees.  We're performing a family linkage analysis to chase down the genes that make these people see the world slightly differently."

Genetics aside, could it be that my mom simply taught me my numbers and letters through a coloring book? "There does appear to be some imprinting," says Arielle Kagan, a Harvard undergraduate who worked in Eagleman's lab this summer. "Some synesthetes end up seeing some colors of their childhood refrigerator magnets. But everyone was exposed to colored letters as children - only synesthetes' brains imprint on those colors and retain them throughout life." Normal brains will separate numbers from colors, processing them in neighboring areas of the brain, she points out.

Since synesthetes appear to have more interaction between neighboring areas, either from increased wiring or lack of inhibition, stimulation of one area activates the other.

Seeing F sharp, Hearing Blue, Tasting Velvet

The most common form of synesthesia is called color-grapheme, which is, like me, someone who experiences a strong color association with letters, words and/or numbers.

It goes something like this: when I see this 6, I know it is black, I see it as black, but I recall it and internalize it as green. (I get very snippy when I see a red 6 - because only a 3 can be red.) The colors are different for each synesthete - my friend experiences 6in a deep blue. The associations are automatic and involuntary.

Typically, synesthetes don't see their colors floating out in space, although this is a matter of debate, Eagleman says. Most describe it as a strong mental association, something like "it is just self-evidently true that a 3 is blue".

Other synesthetes describe the color as being "out there" in the world. But the differences, Eagleman suspects, may be a matter of semantics, description, and/or an issue of the vividness of visual imagery. The problem is that trying to explain what it is like to be synesthetic is like trying to explain sight to a blind person. In any case, synesthetes know when they see a letter written in black ink that it is, in fact, written in black ink. They imagine and retain it, however, in color. The same Rainbow Brite effect occurs with words, months and music. The only advantage I've found in this quirky characteristic is that I can memorize numbers better than most, based on the color palette they form.

Some people have tactile-visual synesthesia, "where they associate shapes, like a woman I interviewed who sees colored patterns when touched on the shoulder," Eagleman explains.

There's my colleague, Susie. She has a mixture of tactile and taste associations. Upon touching or picking up an inanimate object, she gets the taste in her mouth. Velvet isn't bad, "that is, if it is velvet on both sides," she says. And the associations aren't usually unpleasant, "except for terry cloth," she blanches, "that's obvious."

Then there's my friend, the musician. He sees colored shapes when he hears music or certain sounds. Purple triangles may trail through his head when he hears certain chord progressions. He sees stars-very yellow ones-when the cymbals are played. (I find this absurd. Only music in the key of F is yellow and it's harvest gold, at that.)

Spatial placement of numbers, months of the year, and/or days of the week is another form called spatial-sequence synesthesia. "For most of us, February and Wednesday don't have any particular locations in space. But certain types of synesthetes experience precise locations in relation to their bodies for numbers or time units. They can point to the spot where the number 32 is. Or where December is floating. Or where the year 1997 lies," Eagleman says. To study this, he has developed Virtual Reality software to allow his research subjects to physically place their time units exactly where they "see" them.

"Regardless of what type of synesthesia is experienced, it doesn't seem to get in people's way or interfere with their normal lives," Eagleman says. "In fact, one of my students asserts that synesthetes are going to take over the world, because they have extra dimensions along which they can tag things in the world, and typically have stronger memories as a result."

For some, synesthesia confers a talent for coining new metaphors: "cool jazz", "the blues," "loud colors," "sharp cheese."

In my case, I simply remember birthdays better and hear music in more dimensions.

(And, if your phone number happens to be full of 7s and 2s, at least during this fashion season, I'll remember it, because those are hot little numbers for the Fall Collection.)

UPDATED: 10-04-2004

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