Types of Synesthesia

While synesthesia is a combing of the senses, the condition cannot just be described as a paired association of these distinct senses. The five basic senses can be broken down into even more dimensions. For example, some synesthetes in the vision domain may experience color, some may experience shapes, and some may experience movement. Also, the synesthetic experiences may be triggered by stimuli that are not solely sensory, such as shapes, words, letters and numbers (Ward, 2007). Consequently, it is difficult to estimate just how many different types of synesthesia exist. Yet, there are many common forms that can be identified rather easily.

Researchers have formed a way of indicating the type of synesthesia in using the notation: x → y, where “x” is the trigger experience (also called the inducer) and “y” is the “concurrent” (or additional sensory experienced simultaneously).

Grapheme → color

This is the most common form of synesthesia. Individual letters of the alphabet and numbers are collectively called “graphemes”; So, for people with grapheme → color synesthesia, these individual letters of the alphabet and numbers each have an assigned, perceived color.

Sound → color

For sound → color synesthetic individuals, specific tones or sounds elicit synesthetic colors. This type of synesthesia can be broken down into two different categories. One is called the “narrow band” sound → color synesthesia and the other “broad band” sound → color synesthesia. In the “narrow band” sound → color synesthesia (which is more commonly known as music → color synesthesia) musical stimuli, such as key or timbre, produces specific color experiences. For these synesthetes, a particular note may draw out a particular color, or a certain instrument may produce its own unique color experience. For “broad band” sound → color synesthetes, any type of sound in the environment can produce synesthetic colors. A car horn, an alarm clock, or even a dog’s bark could elicit these colorful visual experiences for people with “broad band” sound → color synesthesia (Ward et al, 2006).

Number Form Synesthesia

People with this type of the condition have mental maps of the numeric system. This map involuntarily and automatically appears to number form synesthetes when thinking of numbers (Sagiva et al, 2005)…. Studies have shown that people who experience number form have quicker reaction times in response to saying which of two numbers is larger when arranged in a manner consistent with their mapped number form (Sagiva et al, 2005). This suggests that the number forms are not a recall from learned childhood experiences, but that they are automatically evoked (Sagiva et al, 2005). This ability can be a hindrance however, when numbers are not in line with the way number form synesthetes perceive them.

Spatial Sequence Synesthesia

Spatial-sequence synesthesia is the form of synesthesia in which years, days of the week, months of the year, in addition to numbers, have a specific spatial placement (Krakower, 2004). If asking a spatial-sequence synesthete where a specific number or month lies, he or she perceives a precise location in space, in which that unit lies, usually in relation to the body. Some may perceive lines, circles or spirals in their spatial form, while others have specific patterns that cannot be understood by others (Ward, 2007).

Ordinal-Linguistic Personification

This type of synesthesia is when personalities are evoked synesthetically from the ordered sequences (Simner & Holenstein, 2007). For many synesthetes with OLP, numbers have distinct and fixed personalities. Researcher Mary Calkins presented case study reports in 1893 from individuals who experienced Ordinal-Linguistic Personification. Calkins describes the case of a person whom felt that “T’s are generally crabbed, ungenerous creatures. “U” is a soulless sort of thing. 4 is honest, but … 3 I cannot trust… 9 is dark, a gentleman, tall and graceful, but politic under his suavity” (Calkins,1893).

Lexical → Gustatory

This is one of the rarest forms of synesthesia, in which individual words and spoken language phonemes produce sensations of taste in the mouth (Than, 2006). Many synesthetes with lexical → gustatory can taste a word even before they speak it. Or, when recognizing unfamiliar objects, they can often taste the word before they say it (Than, 2006). One lexical → gustatory synesthete, James Wannerton, reported that his nephew is toffee flavored, his granny tastes of condensed milk, and his next door neighbors are a “mixture of yogurt, jelly beans, and a subtle hint of a waxy substance” (Elliott, 2003).

Related Article



Calkins, M. W. (1893).A statistical study of pseudo-chromesthesia and of mental-forms. American Journal of Psychology. 5:, 439-464.

Elliott, J. (2003). I can taste my words. BBC News, online.

Sagiva, N., Simnerb, J., Collins, J., Butterworth, B., & Ward, J. (2005). What is the relationship between synaesthesia. Elsevier. 2006, 114–128.

Simner , J., & Holenstein, E. (2007). Ordinal linguistic personification as a variant of synesthesia. Journal of Cognitive Neuroscience. 19, 694-703.

Than, K. (2006, November 22). New insight into people who taste words. Live Science, Retrieved March 29, 2009, from http://www.livescience.com/health/061122_word_tastes.html

Ward, J. (2007). Synesthesia research. Retrieved March 28, 2009, from University of Sussex Web site: http://www.syn.sussex.ac.uk/

Ward, J., Huckstep, B., & Tsakanikos, E. (2006). Sound-colour synaesthesia: to what extent does it use cross-modal mechanisms common to us all?. Cortex. 42, 264-280.

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