What sorts of synesthesia exist?
In theory, there can be as many types of synesthesia as there are sensory modality pairings. Some estimate upwards of thirty-five or so different subtypes, such as taste-hearing (hearing a sound produces a taste) and sound-touch (feeling an object produces a sound). Some of these subtypes, however, are far more common than the others. The most common subtypes are color-graphemic, in which letters and/or numbers (and occasionally shapes), produce colors and simple patterns, and color-auditory, in which auditory input, including voices, music, and random noise, produces colors, textures, and shapes. Within these broad categories are many permutations, from those who only experience color in digits to those who have vibrant associations with whole words. For more information on the type and frequency of synesthesia, please see Sean Day’s Synesthesia website, which contains his own documentation of synesthetic phenomena. The synesthetic percepts (what the synesthete experiences as the resu
