Synesthesia, or “joined perception,” is a condition in which sensations from one sense are simultaneously perceived by one or more additional senses. Those who have this condition, called synesthetes, can hear, smell, or taste in colors or shapes. Synesthesia is estimated to occur in anywhere from 1 in 20,000 people to 1 in 200. One of the most common forms of synesthesia involves seeing letters, digits, and words in unique colors. This is grapheme-color synesthesia. The word “grapheme” means a unit (as a letter or digraph—a single sound) of a writing system.
Synesthetes with this condition almost always see a certain color in response to a specific letter, digit, or word. For example, these synesthetes could see the word “library” as brown, the number “2” as orange, or the letter “f” as bright green. These perceptions are specific to each individual, and different synesthetes experience the same number in completely different colors—one person may see the digit “8” as green while others may see it as yellow or blue. Grapheme-color synesthesia, however, does not translate across meaning. The written word “five” is blue but the actual number “5” may be olive green, and “3” may be red but “three” is bright yellow. Plus synesthetes report seeing both the synesthetic color and the color it is printed in (“five” is both blue, the printed color, and bright red, the synesthetic color).
Since digits, letters, and words take on unique colors, synesthetes report having an unusually good memory for passwords, phone numbers, and addresses. However, sometimes they run into issues if colors clash (for example, within a name) or are the same. Colors seem to be stronger when there is a high contrast in printed letters against the background. Color distribution shows some regularities: shorter figures seem to be lighter, in general, than taller ones; the numbers zero and one are often black or white; and the letter “A” is seen as red by 43 percent of synesthetes. A grapheme can also have a gender or character: “L” is an intelligent blue woman and “4” is an ornery chartreuse little boy. When deciding if a name is male or female, synesthetes will answer more slowly if they feel the name is composed of male-like letters.
Functional brain imaging studies show that synesthetic color activates the central visual areas of the brain thought to be involved in color perception. It has been proven that grapheme-color synesthetes seem to have thicker areas of gray matter in certain areas of the brain as well. Additionally, people with synesthesia require only one-third the stimulation of their visual cortex to experience transient flashes of light compared to subjects without synesthesia. It is also known that synesthetes lose their synesthetic perceptions if they experience brain damage. The exact neural mechanism by which colors are automatically linked to alphanumeric characters is still not known. One theory is that synesthesia might result from some kind of cross-wiring between digit and letter processing areas and neighboring color processing areas.
This type of synesthesia is the most widely studied form and research has documented its reality. Synesthetes are not people with overactive imaginations who take metaphorical speech too literally. Two groups of synesthetes with grapheme-color synesthesia have been identified: “projector” synesthetes and “association” synesthetes. “Projector” synesthetes see synesthetic color appearing directly in front of their eyes as if on a projection screen. “Association” synesthetes see the colors in their “mind’s eye” and not outside their bodies.
Synesthetic colors are perceived in the same way that real colors are perceived by those people who do not experience synesthesia. A variety of traditional visual perception tasks show this:
1.When given the task of saying the color of ink a word is printed in as quickly as possible, responses are fast if the synesthetic color matches the ink color and slow if there is a mismatch. This seems to indicate that the synesthete needs to resolve a conflict over which color name to use and demonstrates that synesthesia is automatic.
2.Searching for a “2” among “5”s is difficult due to the visual similarity until color is used. A synesthete has less difficulty because he or she already differentiates using color, so the digits stand out.
3.Arrays of equally spaced letters and digits organize themselves into distinct rows or columns for synesthetes depending on whether they are the same synesthetic color. This is similar to the perceptual grouping nonsynesthetes experience with real colors.
Carolyn Johnson Atwater
See also: Auditory-Tactile Synesthesia; Color Perception; Lexical-Gustatory Synesthesia; Mirror-Touch Synesthesia; Synesthesia; Visual System
Chudler, Eric H. (2016). Synesthesia. Retrieved from https://faculty.washington.edu/chudler/syne.html
Palmeri, Thomas J., Randolph B. Blake, & Ren Marois. (2006). What is synesthesia? Scientific American. Retrieved from http://www.scientificamerican.com/article/what-is-synesthesia/
Than, Ker. (2005). Rare but real: People who feel, taste and hear color. Livescience.com. Retrieved from http://www.livescience.com/169-rare-real-people-feel-taste-hear-color.html