Some people experience red as both a color and a scent. Some people can taste a spicy curry sauce when they hear a specific melody. Some people can both see and hear, and even taste, a silent object just by reading the word: “desk.”
Synesthesia is a condition that describes how senses blend to create a fuller sense of a color, object, taste or feeling. The word synesthesia means literally to join (syn) perceptions (thesia). The symptoms of this condition vary dramatically. For some people, an orchestra playing Tchaikovsky’s "Swan Lake" may suggest a very strong taste of vanilla, whereas some with synesthesia may hear "Swan Lake" and just see colors of green and blue.
Such people, who may experience senses differently than most people do, are termed synesthetes. There are vastly different opinions as to how rare the condition is; some neurologists place it as high as one out of two hundred people experiencing it. It is known, however, that more women than men experience synesthesia. There is a genetic component to synesthesia, and most researchers believe it is carried through a dominant X chromosome, and so it is quite inheritable.
Common types of synesthesia involve numbers and letters relating to particular colors. When asked what color is the number “J,” or what number is “yellow,” a synesthete would not hesitate to answer automatically and without thinking about it. It is believed, then, that when a certain kind of stimulus is presented to the synesthete, neuronal firings and synapses that cover more than one system are activated. This is referred to as “cross wiring” of the brain, as signals cross between two or more synaptic neuronal pathways.
For example, when hearing the word “book,” the brain of the subject may be activated in both visual and olfactory centers. The person reading the word “book” may instantly think of the color green and may smell roses or chocolate. Each person with synesthesia will have different interpretations, but their specific and individual interpretations will remain consistent over time. If one synesthete senses “book” as green, another may sense it as “chocolate pudding.” The different interpretations will still be present even when they are tested months, and, in some cases years, later.
There are many fascinating aspects of synesthesia. Many of those who have the condition are thought to be exceptionally creative. Some leading artists, such as Vasily Kandinsky, and some notable scientists, such as physicist Richard Feynman, have been reported to be synesthetes. Many who have synesthesia are also left-handed, although most people who are left-handed do not report having the condition. When given neurological tests, it is found that people with synesthesia are normal in their neurological functioning, but also average to above-average in intelligence.
Also, some people report that mind-altering hallucinogens can produce the effect of synesthesia among people who had never tasted “purple,” smelled the letter "W" or seen the scent of a tall pine tree. Studying the genetic and biological bases, and especially their fascinating sensations for those with synesthesia, will likely lave many people hungering for the taste of pure blue sky.