A person with synesthesia might feel the flavor of food on her fingertips, sense the letter J as shimmering magenta or the number 5 as emerald green, hear and taste a spouse’s voice as buttery golden brown. Synesthetes rarely talk about their peculiar sensory gift—believing either that everyone else senses the world exactly as they do, or that no one else does. Yet synesthesia occurs in one in twenty people, and is even more common among artists.
In 1980, Richard Cytowic was having dinner at a friend's house, when his host exclaimed, "Oh, dear, there aren't enough points on the chicken." With that casual comment began Cytowic's journey into the condition known as synesthesia.The ten people in one million who are synesthetes are born into a world where one sensation (such as sound) conjures up one or more others (such as taste or color). Although scientists have known about synesthesia for two hundred years, until now the condition has remained a mystery.
For decades, scientists who heard about synesthesia hearing colors, tasting words, seeing colored pain just shrugged their shoulders or rolled their eyes. Now, as irrefutable evidence mounts that some healthy brains really do this, we are forced to ask how this squares with some cherished conceptions of neuroscience. These include binding, modularity, functionalism, blindsight, and consciousness. The good news is that when old theoretical structures fall, new light may flood in. Far from a mere curiosity, synesthesia illuminates a wide swath of mental life.