What Causes Hand Dominance?

Hand dominance is the phenomenon that occurs when one hand is preferred over the other for fine motor skills task. It has been estimated that 85 to 90% of the world’s population is right handed. A select few individuals are known to be ambidextrous, which means they have the ability to handle fine motor skills tasks equally as well with either hand. While there has been much speculation as to what causes people to use one hand over the other, there have been no firm conclusions drawn.

Among the most common theories to explain this phenomenon is that the left side of the brain controls much of the communications functioning and therefore would be natural to control the hand an individual uses to write. The left side of the brain controls the right side of the body.

A number of questions must be answered before this can become a generally accepted theory on hand dominance. For example, if the left side of the brain is so critical in language and therefore controls the dominant hand, why is the entire population not right handed?

Some dominance also appears to be genetically determined, to a certain extent. Even if both parents are left handed, however, there is still only a one in four chance that their child will also be left handed. While that rate is higher than that of the general population, it falls far short of totally explaining the cause.

The environment can also play a role in choosing dominant hands. Desks and other writing materials are normally geared to make it more convenient for those who are right handed. This could help explain why there is so much variance among those who have left handed parents.

Further, it is possible to learn to be ambidextrous. Those who have lost a limb often have to do this, and others simply look at becoming ambidextrous as a goal to achieve. Motor skills can improve with practice, both on the preferred and non-preferred sides. In the end, hand dominance may be a product not only of biology, genetics and environment, but also choice.