Synesthesia is broadly defined as the experience of involuntary sensory crossactivation in which the presentation of a particular stimulus elicits a secondary sensory-perceptual experience (Barnett et al., 2008). Although this phenomenon can be acquired or transient due to trauma or drugs, there is a congenital or developmental form that shows familial patterns. Synesthesia can occur between any 2 sensory modalities, but the most common and best-studied forms of synesthesia involve the association of color with linguistic stimuli such as letters, numbers, or words, or with music ('colored hearing,' 'colored music'; Baron-Cohen et al., 1996). Other less common forms include the induction of tastes by words, the induction of touch by vision, the induction of shapes by tastes, and the personification of numbers (Barnett et al., 2008). [from
OMIM]