What Is Synesthesia?


Synesthesia (or sometimes synaesthesia) is the term given to a complex set of cognitive phenomena, in which stimulus to the senses elicits a simultaneous response in one or more other senses. In other words, a person with synesthesia, on perceiving sound, may also experience sensations of taste, color, smell, etc. in addition to the perceived sounds. The word "synesthesia" comes from the Greek syn, meaning "union," and aesthesis, meaning "sensation". A person with synesthesia is called a synesthete.

 There are many different forms of synesthesia, and some kinds are more common than others. The most common form of synesthesia involves perceiving written letters (graphemes) as being of a specific color, regardless of the ink in which they are printed. So, for instance, one person may always see the letter "A" as red. Estimates of the number of people with this form of synesthesia ranges from 1 in 300 to 1 in 20,000. Many people also associate a sound with color, especially spoken sounds (phonemes.) The ways synesthesia can be expressed is practically endless, however. Touch, taste and smell can all be involved. A friend of mine says that she can't stand spicy foods because when she eats them, she feels pinpricks against her skin, but she loves strawberries and other fruits because when she tastes them it feels like she is brushing against silk.

Synesthesia is said to be found in as many as 1 in 200 people or as few people as 1 in 2,000. The majority of reported synesthesia cases appear to be female, with a tendency also towards left-handedness or ambidexterity. Synesthesia is believed to be an inherited trait carried on the X chromosome, which may explain why it is more common in women. A mother can give an X chromosome carrying the synesthesia genes to either a son or daughter, but a father can only pass it on to a daughter, because a son recieves only a Y chromosome from his father. This means that the chance of receiving an X chromosome carrying the genes is twice as high for a female as it is for a male.

Research is currently being conducted to discover exactly how synesthesia works and developes. It seems to be something synesthetes are born with, as synesthesia has been observed in children as young as three years old. Synesthesia seems to be a cross-linking of senses, with sensory information travelling different pathways in the brain than it does in non-synesthetes. Recently a number of articles have been published on the subject, and it is becoming a hot topic in neurology circles.