Synesthesia

1871

Gustav Theodor Fechner (1801–1887)

Synesthesia is a condition in which the senses flow into each other, like a house without interior walls. It occurs when a person has an experience in one sense that is accompanied by an involuntary experience in one of the other senses. Reported synesthetic experiences involve sound-color, smell-color, and movement-sound. Some synesthetes, or people affected with synesthesia, experience a day of the week as a person or as a color; the possibilities are numerous. One classic case reported by neuroscientist Richard Cytowic involved a friend who experienced flavor as shape and commented about a meal, “There aren’t enough points on the chicken! It is too round.” The most commonly reported synesthesia is number-color (or letter-color)—for example, the number seven is experienced as red.

The earliest research on synesthesia was conducted by the German philosopher Gustav Fechner. His study, published in 1871, included seventy-three synesthetes who all experienced letters as colors. In 1880, the scientist Francis Galton reported that it appears to run in families, a supposition strongly supported by recent research, including studies by Ramachandran and Hubbard (2001) and Grossenbacher and Lovelace (2001). Interest in synesthesia was strong among early psychologists, such as Alfred Binet and Théodore Flournoy, then waned for a number of years, but it has shown resurgence since the 1980s.

Synesthesia is relatively rare: estimates of its occurrence range from one in two thousand to one in two hundred people, and it is found more frequently among artists, poets, musicians, and novelists. As neuroscientist V. S. Ramachandran noted about this connection, “One thing these groups of people have in common is a remarkable facility for linking two seemingly unrelated realms in order to highlight a hidden deep similarity.”

One hypothesis about the cause of synesthesia is that it is due to crosswiring in the brain. For example, the most common synesthesia, number-color, may reflect such crosswiring between two adjacent areas—one that processes number shapes and one that deals with colors. Many prominent neuroscientists believe that further research on synesthesia will greatly expand our understanding of brain functions and human consciousness.

SEE ALSO Psychical Discharges (1941), Neuroplasticity (1948)

An illustration of Russian composer Alexander Scriabin’s key–color association.