The Seasonal Smell of Silver Bells
A wonderful smell stopped me at the open door. My neighbor's entryway was cluttered with freshly cut spruce branches ready to make into Christmas decorations, and the thawing evergreens filled the air with the sharp, nostalgic fragrance of holidays past. For evoking memories, surely there's nothing like the smell of fresh greens.
Ever wonder what fresh reds, blues, or yellows would smell like? If estimated statistics hold true, a couple dozen Alaskans could tell you. One in 25,000 people have a condition known as synesthesia, in which senses we usually think of as separate mysteriously intermingle. When one sense is stimulated, others chime in. For these people, colors may have smells, tastes, or sounds; names can be colored, and numbers can feel rougher or cooler when they're written in Roman numerals instead of Arabic.
When most of us refer to the smell of greens, we're merely referring to the scent of fresh conifer sap. But when people with synesthesia speak of the smell of greens, they mean exactly what they say. In fact, to them some things that most of us associate with green may not smell that way at all, while other things we'd never think of as green strike some of them as greener than spruce needles. According to the journal New Scientist, one British woman identified the smell of grass as having a purple color. Another reported that the whop-whop-whop of a helicopter's rotors draws bright green loops in the air.
These people aren't being fanciful or poetic; what occurs in their brains isn't the same as what transpires in one of the more ordinary 24,999 brains when its possessor thinks of singing the blues or buying a hot-pink scarf.
Nevertheless, some researchers suspect that what goes on in synesthetics' brains could help illuminate how all human brains work. In effect, they think that figuring out where the wires get crossed in synesthesia could help draw the brain's whole wiring diagram.
If they're right, they have a long way to go. Though the condition has been recognized as a medical mystery for better than 300 years, until recently research had established little more than that the condition was real and was most often to be found in left-handed women. Though individuals were consistent in their own synesthetic perceptions (if the name "Lori" tastes like a pencil eraser today, it will taste like a pencil eraser next month--or at least it did for one woman), they rarely agreed with one another (a ringing doorbell may sound scarlet to one, but purple with yellow flashes to another). One interesting exception has been that for more than a century, nearly all synesthetics have agreed that the letter "o" is white, and most say "i" is pale gray or white and "u" is yellow to light brown. This accord holds only for the three vowels, and nobody knows what it means.
Nobody really knows either what another accord among some synesthetics means. Tests made with newly available, high-tech equipment indicate that the blood flow in their brains is peculiar indeed. Generally, the greater the blood flow in some section of the brain, the greater the neuronal activity in that section. While one subject reported a synesthetic experience, overall blood flow in his brain increased, but it decreased markedly in the left hemisphere of his brain. More sensitive tests with six different subjects showed a less surprising pattern, with sound (for example) triggering increased blood flow in those regions usually associated with color perception.
The most interesting question may be why synesthesia is so often letter-based rather than sound-based (the woman who thought "Lori" tasted like a pencil eraser knew that "Laurie" had a lemony taste, for example). Synesthetics may have something to teach us about how learning interacts with our basic sensory equipment--as well as about how fresh reds, blues, and yellows really smell.
