SCIENCE
04/05/2012 07:58 am ET Updated Jun 04, 2012

Synesthesia: What Causes Mix-Up Of Senses? (VIDEO)

Synesthesia is a fascinating neurological condition that causes an individual (proudly called a synesthete) to experience perceptual information through a sense modality that is unlinked to its source. This is a fancy way of saying that synesthetes may hear colors, smell noises, taste shapes, and even feel flavors. This experience is both involuntary and stable over time. Around 100 different types of synesthesia have been documented, and the condition affects nearly four percent of the general population. Synesthesia is thought to be an inherited trait affecting areas of the brain that communicate sensory information to one another.

To learn more about synesthesia, I reached out to Steffie Tomson. Not only does Steffie study synesthesia in the Neuroscience Department of Baylor College of Medicine, but she is also a synesthete. Steffie has grapheme-color synesthesia, which means that she perceives letters and numbers (and even days and weeks) as having very specific colors associated with them.

Do you think you may have synesthesia? You can take a test at synesthete.org to find out. And if you do, you can become an active participant in ongoing science that aims to shed light on this remarkable condition. Watch the video above and/or click below to learn more. And don't forget to leave a comment. Talk nerdy to me!

STEFFIE TOMSON: B is orange whether you say it to me or whether you show it to me. It's just B itself is orange like a banana is yellow. It just is, no matter how you say it.

CARA SANTA MARIA: Hi everybody. Cara Santa Maria here. And that's Steffie Tomson. She's a neuroscientist at Baylor College of Medicine. And she studies synesthesia, a perceptual condition that blurs the lines between sight, sound, touch, smell, and taste. Some synesthetes taste sounds. Others smell shapes. Steffie studies these types and one that's more personal. You see, she also has synesthesia. More specifically. she's a grapheme-color synesthete, meaning that when she sees numbers and letters, they're associated with highly specific colors.

ST: There are lots of types of synesthesias. So there's music-color synesthesia, there's pain-color, there's sound-to-taste synesthesia, there's many different pairings. I think there are about 100 types. So there are many different forms that come in all kinds of different flavors, I guess.

CSM: And some of those flavors are, well, not terribly appetizing.

ST: One synesthete that we know associates the name Eric with the taste of earwax. So he doesn't really like people named Eric because of that. So yeah, it can be any pairing really.

CSM: And if that isn't bizarre enough...

ST: There is a form of synesthesia that has been claimed where people associate colors with orgasm, so that's different. I've not studied that myself, but apparently that does exist.

CSM: Alright. Synesthesia affects an estimated 4% of the population, but many people who have it don't even realize it. In fact, Steffie didn't know she was a synesthete the whole time she was growing up.

ST: I first learned that I have synesthesia when I was an undergraduate at Rice and I was walking by a signpost or something and there was a flier that had 'synesthesia' spelled in big, all cap letters, and every single letter was a different color and all the colors were wrong. And so it kind of took me aback and I thought, well that's bizarre. Who would write that sign? And it turns out that it was actually my current mentor, my current boss right now, was advertising for his studies on synesthesia. And so I tore off one of the fliers and I called him and you know, turned out I had synesthesia which I never knew.

CSM: Synesthesia is thought to have a genetic component, since around 40% of synesthetes have a direct relative with the condition. And German scientists claim that even chimpanzees experience synesthesia. But Steffie and her major professor, Dr. David Eagleman, are studying the neural basis of synesthesia by peering into the brains of people who have it.

ST: We don't actually know what the brain of a synesthete looks just yet. There are several studies that have looked at the structural differences between synesthetes and controls, and there are some differences that come about. Namely in the fusiform gyrus as far as structurally concerned and that particular area is sort of in the occipital lobe in the back of your head. One thing that we have pretty regularly found in studies is that synesthetes, when you show them a number or a letter on a screen that's in black and white let's say, for synesthetes they have activity in the region of their brain that processes color when you show them these black and white numbers and letters, and several studies have found this now. I'm pretty confident in saying that synesthetes experience color in their brain when they're not actually seeing color.

CSM: Learning about the brains of synesthetes may shed light on how some of our most creative minds functioned. Synesthesia has been seen in musicians, artists, authors, mathematicians, and scientists. Did you know that Richard Feynman, one of the best-known physicists of the last century had synesthesia? In his memoir, he wrote: "When I see equations, I see the letters in colors - I don't know why. As I'm talking, I see vague pictures of Bessel functions...with light-tan j's, slightly violet-bluish n's, and dark brown x's flying around. And I wonder what the hell it must look like to the students." Do you associate letters with colors? Can you taste sounds or hear shapes? If so, you can be an active participant in the science that's being done right now.

ST: Our lab has developed a battery of tests to determine who has synesthesia and who doesn't, and it's located at synesthete.org, and anyone can go onto it and click that you have synesthesia and register, and then what it gives you is all of the numbers and letters you know with a color palette, of 16 million colors. And you can go and click which color you have for which number and letter. And so if you're curious if you have synesthesia you should definitely go visit the website at synesthete.org.

CSM: I took the test, and it turns out that my world is pretty black and white. Is yours full of rich, synesthetic associations? Tell me your story by reaching out to me on Twitter, Facebook, or leave your comments right here on the Huffington Post. Come on, talk nerdy to me!

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