Synesthesia - Hearing Colors and Tasting Shapes

The word synesthesia means "to perceive together" in Greek. It is the name of a certain sensory condition in which a stimulus directed to affect one sense actually affects another that is somewhat unrelated. A synesthete might, for example, taste shapes, smell emotion, see sounds, conceptualize abstract ideas (such as math) as occupying the space around them in projecting shapes. The most common form of synethesia is the ability to see sounds.

Synesthesia, once thought to be a mental illness, is now looking to have a very identifiable biological and genetic root. Recorded research of this condition dates back to the 19th century; however, the behaviorism movement caused it to be tossed aside until the 1970's. Researchers have conducted tests over a course of generations in which proclaimed synesthetes are given a word and asked to describe the color that they associate with that word. Ninety-percent of participants consistently correlate the same colors with each word while non-synesthete participants are only consistant with their answers twenty percent of the time.

Today, researchers have imaging techniques that enable them to trace the brain activity of a synesthete. With the use of MRIs, scientists are able to observe the significantly increased activity in the visual areas of the brain of those who report "colored hearing" compared to those who do not have this condition. Something is obviously occurring biologically, but what is causing this?

Many theories have been formed in an attempt to explain this phenomenon. A century ago, researchers believed synesthesia was a result of "crossed wires" in the brain. Today, there are competing theories, for example, some scientists believe that synesthesia is caused by a genetically driven excess of neural connections in the brain. Another theory says that all humans are born with neural connections that allow synesthesia but that most lose this connection as we grow. Others have come up with a "feed backward" theory which claims that there is a disruption in the process by which our brains filter initial information from multi-sensory areas into information that we perceive as the appropriate sense for that particular situation. Another possibility that has been considered is that existing connections become temporarily altered from time to time in synesthetes; in the same way that our neural activity can be altered by hallucinogenic drugs.

Research pertaining to synesthesia further bridges the gap between "hard" and "soft" sciences; gaining respect for the field of psychology. Carpinter's article provides a history of research that has been done on the subject and theories that are being researched currently. This article demonstrates that synesthesia is not only a fascinating condition on its own, but learning about its causes and affects might help us understand the workings of the nervous system, cognition, genetics.