Synesthesia was first referenced in 1710, describing a blind man who perceived sound-induced colored visions. At some point during its history, synesthetes were seen as mentally defective or artistically gifted. For most, it was an embarrassment and for some it still is. Doctors and researchers were the only ones to publicly describe their symptoms for many years. Presently, those who experience synesthesia do not see it as an obstacle or something that hinders their functioning but some believe that they may be mentally ill.
Synesthesia can combine any or all five of the senses.
The most common combination is found with sight and sound, which is also referred to as colored hearing. For synesthetes with colored hearing, sound causes them to see moving colors and shapes that are externally projected. As described by one synesthete, letters, numbers, names, and simply words in general cause her to see a flash of colors. She also said that the letter does not appear in color but rather there is a flash of color. The letters do not evoke the same color for everyone.