The left brain hemisphere is indebted for the functions of the brain which is associated with reading and writing. Some people with dyslexia have a dominant right hemisphere, which, apart from dyslexia, can lead to acquired left-handedness.
The first research attempting to link dyslexia with the dominant brain hemisphere was performed by Orton in 1937. From this year, research is continuing in this area. About 85% of people with right-hand dominance have the dominant left hemisphere, which is in charge of speaking, however, most of those whose left hand is dominant also have the left hemisphere as dominant.
Between the dominance of the arm and the dominance of the brain hemisphere there is high association. It has been observed that in children with undeterminated hand dominance, a greater number of dyslexics are observed. In addition to dyslexia, left-handed children often have difficulty learning.
We should also mention the studies carried out by Gotestam on homosexuals. He questioned the dominance of the hand, the existence of dyslexia, the interests of music, art, and creativity. Analysis have shown that 13.9% of homosexuals are left-handed, 8.6% have dyslexia. Issues related to creativity pointed to a high level of activities in the field of music and painting. Brown and associates examined children with right hemisphere injuries and children with left hemisphere injuries. They also examined the correlation of the injured hemisphere with dyslexia and hyperactive behavior. The results of their research show that children with injuries to the left hemisphere manifest poor performance of the actions involving the right side of the body and often have dyslexia. Children with right hemisphere damage manifest significantly less performing exercises involving the left side of the body and hyperactive behavior.
From this, researchers concluded that developmental dyslexia may be caused by mild left hemisphere dysfunction, and developmental hyperactivity may be caused by right hemisphere dysfunction.