The Cognitive Functioning of Right Handed vs. Left Handed People is compared in A Monitor on Psychology article by Monitor Staff writer Michael Price, (Volume 40, No. 1 December 2009).
Michael Price explains in this article that right handed people have a left hemisphere dominant brain while left handed people have a right hemisphere dominant brain. In most people the dominant brain side specializes strongly in speech and language, while the other side specializes in processing images and emotions. This specialization is present in 95% of right handed people, but only about 20% of left handed people have brains that divide up cognitive functions so rigidly. Within each group, some people have a strongly lateralized brain, while others have more symmetrical brains. The article refers to a study by Michael Corballis, Ph.D., a psychologist at the University of Aukland in New Zealand. Dr. Corballis states that there is an advantage in the lateral specialization.