Friday, April 13, 2007

The Seventh Sense


From childhood, we are taught that the human body has five senses. I'm sure we can all recite them: sight, hearing, touch, taste, and smell. This list has remained unchanged since the time of Aristotle. To most people, a "sixth sense" refers either to one outside the realm of the scientific, or one that simply does not exist in most humans.
However, ask a neurologist how many senses the human body has, and you might get a surprising answer. Many identify nine or more senses- some listing as many as twenty-one. The first category of senses is the "special" senses, including the familiar sight, hearing, taste, and smell. The second category is made up of the somatic senses, which we usually lump under "touch"- including our perception of pressure, heat, and pain. The third category, however, is not nearly as well-known. These are the interoceptive senses- those that deal with data originating in the body itself.
It is fairly obvious what happens to a person when a sense fails. Many members of society are missing one or more senses. It is common knowledge that blindness is the absence of sight. Deafness, of hearing. Everyone knows what it's like to lose taste and smell as well; this loss accompanies every head cold. But what happens when the body loses knowledge of itself is a far stranger occurrence.

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