Why Do People Have Dominant Hands?
Although there is no consensus why people have dominant hands, there seems to be no shortage of theories regarding how handedness comes about. There are four recognized types of handedness.
The majority of the world's population is right handed. The next most common is left handedness, which as much as 10% of the population is thought to be. Mixed handedness is when some individuals will use their right hand for one activity, like writing, and their left for tennis. Finally, there is ambidexterity, which is very rare. Being truly ambidextrous means that both hands are used equally for all activities. The flip side of ambidexterity is ambilevous or ambisinister in which an individual is equally poor when using either hand.
One theory that is just starting to flesh itself out says that dominant hands is a result of both hands working together. This is called bilateral coordination. It's a process in which both hands are working together to accomplish a task. What you have is a worker hand, thought of traditionally as the dominant hand, that will perform the fine motor task. Your non-dominant hand is thought of as the helper hand and performs gross motor skills, like stabilizing an object.
When talking about dominant hands, the most commonly accepted theory is division of labor. This refers to the hemispheres of the brain and how information is processed and divided between the hemispheres and fine motor skills in the hands, eyes, feet, and ears. It's generally known that speaking and communication activities in right handed people are performed in the left hemisphere of the brain. The major argument against this theory holds that what's true of right handed people should be opposite for left handed people. In other words, left-handed people should process language in the right hemisphere of their brain. That is not entirely true, which makes this theory flawed.
In 2007, scientists looking for a left handedness gene found LRRTM1. This gene gives some credibility to the thought that having dominant hands might be genetic. This theory is also just being tested for validity because the gene carries other traits as well. However there is still only about a 1 in 4 chance of having a left handed child if both parents are left handed.
Having dominant hands might not seem like such an important thing when you're writing a check for the groceries, but the implications go pretty deep. Scientists believe that there is a relationship between learning and handedness. Finding answers to dominant hands could unlock seemingly unrelated issues like dyslexia and stuttering.
Written by Kris Roudebush
