Synesthetes, or people who experience the phenomenon of synesthesia, have "cross-linked" senses, such that a stimulus in one sense modality may cause a sensation in another. This paper presents a brief history of this interesting phenomenon, from the synesthetic motifs of the Pythagoreans to more recent neurobiological studies elucidating the mechanisms behind how the typically distinct five senses can become inextricably entwined.
"Colorful Noises and Tasty Words: A Historical Examination of the Phenomenon of Synesthesia,"
Sound Neuroscience: An Undergraduate Neuroscience Journal: Vol. 1
, Article 10.
Available at: http://soundideas.pugetsound.edu/soundneuroscience/vol1/iss1/10