Synesthesia

Synesthesia is a neurological phenomenon in which stimulation of one sense—like hearing a sound—causes a simultaneous perception in another sense—like seeing a color. It is estimated that around 4 percent of the population experiences synesthesia. It is not fully understood, but it is believed to involve increased connections between the brain's perceptual areas. Synesthesia has been used for centuries as a creative tool in art, music, and literature. It has also been studied for potential therapeutic applications, including helping to improve memory and attention, and there is ongoing research into its applications for pain relief.