Imagine a world where the sound of music would make you see colors. Where the note B is sparkling silver and D flat is a wondrous, pure periwinkle. Where the taste of food has a distinctive shape and where the sound of words can leave a bad taste. Even the calendar -- days, months and years -- can generate specific 3-D images.
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That's the world of Laura Rosser, 24, and others who have synesthesia, in which one sense -- taste, sight, hearing, touch or smell -- gets jumbled with another, creating what Dr. Richard Cytowic, a neurologist, describes as a blending of the senses.
"My voice, for example, is not only something that you hear but also something that you might see or taste or feel as a physical touch," Cytowic said.
Rosser sees every note of the piano she plays as a distinct color. "E flat is turquoise. Very warm turquoise," Rosser said. "F sharp is yellow-green." When Rosser plays many notes together, she said the colors "sort of merge into each other."
Synesthesia isn't just people getting a bit poetic about their world. The brains of people with the condition are actually wired differently.
Cytowic said people with synesthesia have a "different texture of reality."
Seeing Numbers in Color
Rosser sees numbers as colors, too. To her, "Twos are orange and [fives] are red." Another woman who has synesthesia, Crista Kostenko,27, sees the same numbers but in different colors. "My fives are red and my twos are yellow."
Rosser and sisters Evin Linn, 24, and Kostenko see more than just black letters. Since they were children, they've had cross talk going on in their brains, meaning every letter is associated with a distinct, unchanging color.
"What this shows is that synesthesia is both automatic and involuntary," Cytowic said. "So they can't really control it. It's just there. It's something that happens to you. You don't do anything to make it happen."
They see colored numbers, too, and the colors are very specific. When ABC News asked Rosser, Linn and Kostenko to show us how they see the number eight by selecting from hundreds of paint samples, they had a hard time finding a match.
"It's between gentle violet and exotic purple," Rosser said. "It's like majestic violet. But it's midnight navy, more between [the two]," Kostenko said. "It's more of a pink. Sort of a combination between rosy blush and spring tulips," Linn said.
The colors are always the same from the day they're born till the day they die. In case you don't believe them, there's scientific proof.
"It's a real color experience that's as vivid and real as the colors that you and I see ordinarily in the world -- it's just that it's being evoked in a highly unusual way," said Randolph Blake, an ABC News consultant, who, along with a team at Vanderbilt University, is researching Rosser's brain.
As black letters flash before her eyes, Rosser records the colors she sees. Amazingly, images of her brain show the color areas are active. These are areas that would not light up in other people's brains.
"The hypothesis is that there's some unusually strong connections between areas of her brain that aren't so strongly connected in our brains -- so strong, that when she's looking at a letter, it actually automatically activates that color area," Blake said.
So, where do those unusual connections come from? One theory is that we all have them when we're babies, when the brain makes millions of new synaptic connections a second. As we grow older, those connections get pruned back as the senses separate. But in synesthetes, more of that wiring just stays in place.
Linn and Kostenko can also connect colors and geometric shapes with food. Take Swiss cheese.
For Linn, it has a "very thin line going through it," while Kostenko sees "an olive color" that's "kind of wavy."
As for blue cheese, Linn said "it's pointy." Kostenko said she can see why her sister sees blue cheese as pointy, but for her "it's a lot of little balls."
When it comes to food, it can get even stranger for British pub owner James Wannerton, who tastes almost every word he hears, even the words of his customers' orders.
"Somebody will come in, they then order, say, a pint of [beer]. I get the bacon rind taste. They then order a packet of roasted nuts, and I don't get roasted nuts, I get some sort of peculiar burned meat taste. Then [I] have to give them their change -- change invariably tastes of processed cheese -- a cheesy taste," Wannerton said.
And some of the flavors can be very unpleasant. Take the name Derek.
"Ugh, it's horrible," Wannerton adds. "It's earwax."
Runs in Families
There are other cases of synesthesia running in families. For as long as they can remember, sisters Trish Goodwin, 23, and Molly Altobelli, 25, have pictured numbers, months and days of the week as 3-D pictures in space, which they re-create in virtual reality at the University of Texas. "It was strange to find out that not everybody thinks of numbers this way and not everybody has a spatial layout for the days of the week," Goodwin said.
Theysaid it can help in keeping track of appointments, but the two sisters have very different ways of seeing the same thing.
"I sort of picture them out in front of me and they're kind of in an oval, and then I sort of zoom in on it and sort of mentally mark that day," Altobelli said.
"I do the same thing," Goodwin said, "but 'cause I'm picturing myself in a spot on the sequence, I can see that it's like two days away or it's almost right in front of me."
In addition to Goodwin and Altobelli, their younger sister, Kate, and mother, Elisa, both have synesthesia. Researchers have been studying the family, looking for a genetic clue. There are two ways to explain the trait, says David Eagleman, at the University of Texas Houston Medical School.
"One of them is that there's more wiring in a synesthete's brain. The other hypothesis is that the wiring is the same in everybody but something about this gene is causing there to be more cross talk among areas," Eagleman said.
While this sensory cross talk may be more hardwired in the synesthete's brain, perhaps there's a little remnant of it in all of us, said Cytowic.
"I see it as a gift, as a sort of spiritual god thing that enables more intuition, whether it's musical or even with people to be able to see some extra things out there," said Rosser. Without synethesia, she said she'd be living in a world that was just monochromatic.