Synaesthesia is the confusion or conflation of sensory modalities, where one sense is experienced or described in terms of another as in Charles Baudelaire’s simile “perfumes sweet as oboes, green as prairies.” Synaesthesia captures an already existing tendency in language to blend the senses as in “sweet melody,“ ”velvety voice,” or “loud colors,” and psychologists have conducted studies that show our shared experience of weak audiovisual associations between low pitch and darker colors, or high pitch and lighter colors. In a strictly neurological sense, synaesthesia is a perceptual condition in which the stimulation of one sensory system (for example, hearing) triggers sensations in another sensory system (for example, vision). Cross-sensory associations form one-to-one correspondences that are stable, delicately nuanced, and highly individual. For instance, a synaesthete may experience the timbre of violins as lime green, or the pitch A as burgundy. Synaesthetic associations occur as involuntary, automatic, and emotional responses to sensory stimuli. They persist throughout life and often aid memory: some synaesthetes reliably remember historical dates thanks to their color-to-number associations. The prevalence of synaesthesia has been contested over time, with varying ratios of synaesthetes to nonsynaesthetes of 1 in 2,000, 1 in 100 for colored letters and numbers in recent studies, and even 1 in 23 for all types of synaesthesia.