WHY ARE SOME PEOPLE LEFT HANDED?
Handedness is a word that means you have a tendency or preference to use either your left hand or your right hand more frequently than the other. The hand a person comes to prefer is determined, in part, by heredity.
The exact mechanisms by which the genes affect handedness are still unknown. We do know, however, that two right handed persons can have a left handed child, or that two left handed parents can have a right handed child.
About 75 percent of the human population is strongly right handed and approximately 90 percent is predominantly right handed. Among the remaining 10 percent, a great deal of variability exists, with some people being strong left handed and with some other people being left handed for some activities but right handed for others.
Scientific studies conducted during the early 1980s suggest that differences in left and right handers in patterns of brain organization may be associated with differences in skills, aptitudes and perhaps even personalities. In the large majority of right handers about 99 percent speech is controlled by the left side of the brain. The right hemisphere of the brain is usually specialized for recognizing and remembering factors and understanding relationships in space.
In left handers, the pattern of brain organization is unpredictable. About 65 to 70 percent of left handers have speech controlled by the left hemisphere of the brain, as is the case for right handers, but in 30 to 35 percent of left handers, speech is controlled by the right hemisphere of the brain.
In some left handers, both hemispheres of the brain are capable of controlling speech.
Among some of the famous left handers of the past are American statesman Benjamin Franklin, British author and mathematician Lewis Carroll and the great Italian artist Leonardo da Vinci.
Sometimes a physical injury may be involved in determining whether a person is left or right handed. During the birth process, the region of the brain controlling the hand is sometimes damaged, so that a child who would have been right handed without such damage becomes left handed.
Social pressures have had a considerable effect on handedness. A few decades ago in the United States, using the left hand for writing was strongly discouraged and only two percent of the population wrote with the left hand. Today in Taiwan, only one percent of the population writes with the left hand because left handedness is socially condemned.
The French word for "left " is "gauche," a word also commonly used to mean "awkward." Left handers are, of course, no more awkward than right handers. Any awkwardness or psychological disturbances observed in left handers in the past could well be attributed to the problems that were created for them by an intolerant society.
In recent years society has become tolerant. In American schools, no student inclined to be left handed is forced to use only his right hand.