SYNESTHESIA (literally, “feeling to- gether”)

An experience in which two senses respond when only one is stimulated; also called crossed perception.About 5 to 10 per cent of the general population are said to experience this dramatic interaction of the senses. Synesthesia is also experienced by individuals under the influence of hallucinogens such as mescaline and LSD, and occasionally by patients undergoing epileptic seizures. In the most common type, called chromesthesia, sounds, and sometimes tastes, odors and sensations of heat and cold or pain, are experienced as colors. This is not merely a verbal association of colors with sounds or other sensory experiences. Rather, the perception of color actually accompanies these sensations; the individual really sees a definite color when he hears a particular sound. Langfeld (1914) investigated a case of chromesthesia twice within a period of seven years and found highly consistent sound- color relationships: the musical note “c” was always experienced as red, “f” as pink, and “g” as clear blue.Other investigations have uncovered the following relationships in color hearing: (a) quickening the tempo or raising the pitch increases the brightness of the image; (b) syncopated music produces jagged lines; harmonious rpusic, flowing and graceful lines; (c) different musical instruments produce different colored lights; and (d) increasing the volume of sound increases the size of the images. In most cases the music has to be actually present, but in some instances the act of recalling music can itself produce colored images. (Karwoski and Odbert, 1938)The mechanism that lies behind these experiences is still unknown. Some investigators, however, have suggested that synesthesia is a vestige of an early stage of development in which the infant or young animal does not distinguish between specific sights, sounds and tactile sensations, but only between such general dimensions as light or dark, bright or dull, smooth or rough. This theory gains some support from common expressions such as “brown taste,” “loud colors,” and “dark sounds.”