Introduction

Synesthesia is a unique experience in which "one sensation involuntarily conjures up another" that affects ten out of every million people (Cytowic 6). Synesthesia is most commonly manifested in the synesthete's association of certain numbers or letters of the alphabet with specific colors or of certain sounds or types of music with specific colors or shapes. Synesthetes always associate the same color with the same letter, number, or sound. For example, twos are always red, or Q's are always lavender to a particular person who experiences synesthesia. However, not all synesthetes agree on what color each letter, number, or sound is. Synesthesia is not a metaphorical description. Rather, it is a description of what the synesthete senses as reality.

Background and History of Synesthesia

Although a remarkable and involuntary experience, synesthesia affects healthy people of normal intelligence. Because its occurrence is rare, synesthesia has often been viewed as a dysfunctional trait or an indication of abnormally high intelligence. Most often, synesthesia does occur in people who are of average or above-average intelligence. Due to the subjecteve nature of synesthetic perceptions, many people are skeptical of its legitimacy. However, one must keep in mind that pain, headaches, and dizzy spells are of the same subjective nature as synesthesia, yet are readily accepted as legitimate by the general public and neurologists alike.

In 1710 the first medical reference to synesthesia was made by Thomas Woolhouse, an English opthalmologist. Woolhouse discussed the situation of a blind man who expereienced colored visions upon hearing certain sounds. Although neurologists did not approach the subject of synesthesia for quite a long time, synesthesia caught great interest within the scientific and artistic communities during the nineteenth century. It was around this time that "The issue that Synesthesia is a product of the brain (like all sensation), rather than a product of the imagination, was settled at the turn of the century," (Cytowic 9).

Sir Isaac Newton took great interest in color and its relation to sound and actually attempted to create mathematical formulas to link the frequencies of sound waves with their analogous wavelength of light. Although his formulas never worked out, Newton's work inspired generations of scientists, artists, and philosophers to study color.

Two of the first books to discuss synesthesia were published in French in 1890 and in German in 1927. The books were titled Colored Hearing and Colored Hearing and the Synesthetic Factor of Experience, respectively.

Diagnosing Synesthesia

There are four factors which may lead to a diagnosis of synesthesia.

1. Synesthetic experiences are insuppressible and involuntary. As children, synesthetes often do not realize that their perceptions are any different from anyone else's perceptions. One synesthete described his experience of synesthetic images as such: "...the shapes [the subject visualizes upon hearing sounds] are not distinct from hearing -- they are part of what hearing is," (Cytowic 76).

2. Synesthetic percepts are generic, rather than complicated scenes.

3. The synesthete consistently associates the same color with the same sound or letter or number.

4. The synesthete is convinced that what he experiences is real. "Synaesthetic percepts are perceived by the synaesthete as projected externally. In visual forms the synaesthetic percept is felt to be close to he face, while in kinaesthetic forms it is felt to occupy the space immediately surrounding the body," (Dann 6).

(Cytowic 77).

Process of Synesthesia in the Brain

Scientists are still searching for a complete explanation of how and why synesthesia occurs.

According to Richard Cytowic, M.D., "...parts of the brain get disconnected from one another (as they do in release hallucinations), causing normal processes of the limbic sysem to be released, bared to consciousness, and experienced as Syneshesia. In other words, a stimulus causes a rebalancing of regional metabolism."

Conclusions

Although it is a rare phenomenon, synesthesia is an intriguing subject. Many discoveries about the relationship between the senses, especially between color vision and sound, have been made over the past few centuries. However, synesthesia remains mysterious. Scientists and philosophers have yet to understand exactly why individual synesthetes perceive such unique color patterns and what exactly causes synesthesia to occur.

Links

The Synesthetic Experience

American Synesthesia Association

Synesthesia: Phenomenology and Neuropsychology

The International Synaesthesia Association

Other References

Ackerman, Diane. A Natural History of the Senses. Random House: New York, 1990.

Cytowic, Richard E., M.D. The Man Who Tasted Shapes. MIT Press: Cambridge, 1999.

Dann, Kevin T. Bright Colors Falsely Seen: Synesthesia and the Search for Transcendental Knowledge. Yale Press: New Haven, 1998.

Duffy, Patricia Lynne. Blue Cats and Chartreuse Kittens: How Synesthetes Color Their Worlds. Times Books: New York, 2001.