While most of us experience the world through orderly senses, for some people, two or more senses mix together. This phenomenon is called synesteshia. People with synesthesia often see letters and words as colored. Ther also may feel or taste sounds or hear or taste shapes: a musical note that tastes like pickles, a taste of chicken that feels "round", or the sound of a guitar that feels like a soft touch on a person`s leg.One aspect of the phenomenon is that different people do not have the same experience. For example, letters do not produce the same color for everyone.
The Biological Basis of Synesthesia
Some scientists believe that synesthesia results from "crossed-wiring" in the brain.
They hypothesize that in synesthetes, neurons and synapses that are "supposed" to be contained within one sensory system cross to another sensory system. It is unclear why this might happen but some researchers believe that these
crossed connections are present in everyone at birth, and 
only later are the connections refined.
In some studies, infants respond to sensory stimuli in a way that researchers think may involve synesthetic perceptions.
It is hypothesized by these researchers that many children have crossed connections and later lose them. Adult synesthetesmay have simply retained these crossed connections.
