In the 19th century, they called it “colored hearing”—letters and words, when spoken, took on mental weight and shimmered with color in the mind’s eye. For Miss C., who was interviewed in 1892, “n” was nut-brown, “w” a pinkish heliotrope, and her own initial, “c” a vivid lemon yellow, “the brightest color of all.”

Miss C. had no explanation for her peculiarity. In fact, until she was approached by the students of Wellesley College psychology professor Mary Calkins, she hadn’t even thought of it as a peculiarity. She just assumed everybody saw letters in color. There was a theory at the time that colored hearing might be the result of associations learned in childhood. Maybe Miss C. had once played with