Synesthesia

Synesthesia (n.): a concomitant sensation, especially a subjective sensation or image of a sense (as of color) other than the one (as of sound) being stimulated; the condition marked by the experience of such sensations.

Synesthesia comes from the Greek words syn, meaning "with, together," and aisthesis, meaning "sensation." Synesthesia is the medical condition of someone experiencing two sensations when most others experience one. Some synesthetes (a synesthete is someone with synesthesia) hear as well as feel a texture, or taste as well as see a color. Also, some synesthetes see color when they hear a certain consonant sound, or always see a letter in a certain color. Synesthesia is likely hereditary, but is not transmitted all of the time.

Synesthesia occurs when sensory regions in the brain have increased communications. When two areas of the brain that deal with the senses, e.g. hearing and seeing, have increased communications, if one of those areas is stimulated, then  it stimulates the other area. For example, if the area that deals with hearing is stimulated by say music, the area that deals with sight will also be stimulated and the synesthete will perceive a color going along with the music. As well as being hereditary, synesthesia can also be caused by drugs, sensory depredation  and/or brain damage.

Bibliography

Brang, David. "Survival of the Synesthesia Gene: Why Do People Hear Colors and Taste Words?" PLOS Biology. 22 November 2011. PLOS. 26 March 2013. <http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001205>

Day, Sean A. "Synesthesia." Daysyn.com. 20 March 2013. Day, Sean A. 26 March 2013. <http://www.daysyn.com/index.html>

Imagine. "Hearing in Color." Imagine March/April 2013: 4-5.