Handedness is a very complicating, multifactorial trait. How handedness is determined, advantages to specific hands, and ambidexterity are topics of research. Handedness is found to be indirectly related to genetics in that certain genes influence the brain. The brain hemispheres contribute to the bias toward or away from right handedness. Genetics, neuroscience, and environmental factors all play a role.
Ambidexterity is recently given a negative stigma as some research supports that it affects the asymmetry of the brain by making the hemispheres compete. This further causes developmental deficits. With this risk, I do not think it is important to encourage ambidexterity through games or sports. There does not seem to be a solid link in disadvantages between left and right handedness, other than that right handedness is more common.
Handedness is a seemingly simple idea that becomes very complex when going into the in-depth ideas of genes and learned traits. Do you ever wonder why you are right or left handed? Or maybe even wish you could use both hands with the same dominance and be ambidextrous? This paper will discuss some research behind these different ideas of handedness to support whether it is genetic or learned, and which behavior is the most advantageous, if any. Whether or not one can learn to be ambidextrous, how to learn, or should learn to do so will be discovered by the studies of the brain, genetics, and learned traits.
These questions are all very controversial due to the highly complicated nature of our genes working together and the traits we acquire through models and practice. The hypothesis behind these topics is that handedness is a genetic trait with a very complicated background, but one can also learn and adapt to become ambidextrous. This learned behavior may not be beneficial to the brain function.
Materials and Methods
Scientific articles and blogs are read and applied to support or reject the idea of genetic handedness and advantages of either hand or ambidexterity. These articles weigh both sides of the idea and discuss the complicated details behind the research. Lots of research has been done on this idea, but not all is replicated and confirmed. Research on the benefits or disadvantages of ambidexterity is very hard to find, which may be contributed to the small population of people who are ambidextrous. As stated, this topic is very controversial and still in debate.
After many studies, handedness is now considered to be a multifactorial trait due to its many determining factors instead of one single gene. It may be determined by a mix of environment and genetic influences. If it had been a monogenic trait, left handedness would no longer exist due to the vast domination of right handedness. There is thought to be at least 40 genes that contribute to handedness and maybe 60 more undiscovered (Ocklenburg, Beste, Güntürkün, 2013).
The human body is thought to be designed with left and right symmetry in some cases, but not when it comes to the brain. Handedness seems to develop out of this realm and have an asymmetrical linkage. A gene that provides this information is PCSK6. It aids in the determination of left and right asymmetry in bilaterians.
In a study of mice, a mutation in this gene causes normal asymmetry to affect organs to grow on the incorrect side of the body. This proposes an idea of how this gene is linked to the molecular means of the asymmetry hypothesized in handedness of a developing human (Ocklenburg et al., 2013). Right handedness is thought to be controlled by the left brain, as is the trait of language. A study shows that mutations in the PCSK6 gene caused a reading disability. This leads to the idea that language in humans may have evolved through gestures of handedness. Studying this gene and others results that 25% of handedness is currently estimated to be influenced by genes. The idea is really that the gene determines whether or not the default right handedness will be expressed (Ocklenburg et al., 2013).
This is saying that there is no gene that influences for left handedness, but a bias away from the right-handed gene causes left handedness to occur by chance. “Another finding that supports the assumption that handedness is to some extent genetically determined is the fact that identical twins are more likely to be concordant for hand preference than non-identical twins” (Ocklenburg et al., 2013).
There seems to be a relationship between the strength of the side of handedness and degree the language dominates the contralateral side of the brain in healthy people. This language lateralization study determines that a strong right-handed person will be language dominate in the left hemisphere of the brain as the left hemisphere is connected to the use of the right hand. The same goes for the left hand with the right hemisphere of the brain. Not all of these studies have been replicated but bring about how brain lateralization correlates with handedness (Knecht et al., 2000).
A study in school age children shows that the number of participants with right handedness increases with age. This supports two hypotheses. One is that environmental factors influence in handedness, as right handedness dominates the population. The other is that these participants are still maturing as the brain develops, up until the age of 30 (Scharoun & Bryden, 2014).
Studies have shown that ambidextrous desire has decreased because of the risk of developmental conditions and issues with memory retrieval and logical reasoning. These studies support that it may be advantageous to train the nondominant hand when needed for a certain skill, but not to the point of making the hemispheres of the brain compete, as they were not developed to work that way (Corballis, n.d.).
As discussed above, handedness correlates with hemispheres of the brain. There is thought to be a connection between this, ambidexterity and the learning deficits that seem to come along with it. The lateralization in the brain of a right-handed person is different than that of an ambidextrous person causing association with disorders such as ADHD. This is supported by a study of grade school children and their performance in school, language, and behavior. It shows deficits in these categories of ambidextrous children (Bryner, 2010).
The population of the world is dominated by right-handed people at 90%, left-handed at 9%, and ambidextrous at about 1%. Hand preference is seemingly determining to what degree a person prefers their right or left hand. A right-handed individual prefers their dominant hand more strongly than does a left-handed individual due to the bias away from right handedness present in the left-handed subject. A person whose genetic makeup has a less bias toward right handedness may see someone else using their left hand and reinforce the use of it. The genes do not directly affect handedness but are important in the determination of the brain development. Brain development is related to handedness through the asymmetry of hemispheres as described above. This is an example of how handedness begins with heredity, but as with many things in life, we learn by watching others and idolizing. Many of our innate traits are solidified by learned traits or even modified to an extent.
The twin study and many gene studies support the hypothesis that handedness is inherited, but also is influenced by many other factors including more genes and environmental factors. I think it is very important to realize that being able to use both hands does not make you ambidextrous as this is using both hands equally, causing the brain hemispheres to become more symmetrical. When a person breaks an arm and is forced to use their non-dominant hand, during this time period they are not ambidextrous.
Having the ability to use the other hand, but not to the extent of the dominant hand does not make a person ambidextrous. The brain is a complex organ that controls our entire body. I think that it was made with asymmetry to aid in our function as human beings. A person can learn to become ambidextrous, but studies support that it is disadvantageous to their brain function. As with many learned traits, time and practice can change most things.
Ambidexterity would be easier learnt at a young age as this is when handedness is thought to be decided, before the brain completely matures. I do not think we should train all people to use both hands, as I believe the brain was meant for us to use one hand for dominance. I do not think being left or right handed is better either way, right handedness is just more common. This makes items such as scissors and ball gloves less interchangeable for the left handers, which may be a slight disadvantage. We could develop a sport or game to train kids’ dominance in both hands, but I do not think we should.
The brain is designed in such an intricate way to amazingly power our complicated body, and I think ambidexterity is trying to change this system we were born with. I would not want to be ambidextrous. I have had times I was required to use my non-dominant hand and was just fine doing so. I prefer to just depend on my right side, as this is all I have ever known, and learning about the functional deficits of ambidexterity confirms this opinion. As explained by this paper, the complexity of this topic does not simplify. In my opinion, it comes down to a matter of each person deciding their stance. Personally, I would not want to be ambidextrous because I am satisfied with my right hand and like to be a part of the larger population without the risk of developmental issues.
With all of this research and discussion, unfortunately a straight answer is not given. Many of these studies have not been replicated, there is only a small amount completed in healthy individuals, there are not many complete studies of genes and neuronal relationships for this trait, there are many undiscovered genes thought to influence handedness, and the multifactorial trait is just complicating. This is frustrating, but also the reason I love the always engaging, never perfect world of science and discovery. There are always new things to learn and new ideas to contemplate!
Bryner, J. (2010, January 25). Ambidextrous Children May Have More Problems in School. Retrieved September 21, 2018, from https://www.livescience.com/8044-ambidextrous-children-problems-school.html
Corballis, M. (n.d.). Can Training to Become Ambidextrous Improve Brain Function? Retrieved September 21, 2018, from https://www.scientificamerican.com/article/can-training-to-become-ambidextrous-improve-brain-function/
Knecht, S., Dräger, B., Deppe, M., Bobe, L., Lohmann, H., Flöel, A., Ringelstein, E.-B., & Henningsen, H. (2000). Handedness and hemispheric language dominance in healthy humans. Brain, 123(12), 2512–2518. https://doi.org/10.1093/brain/123.12.2512
Ocklenburg, S., Beste, C., & Güntürkün, O. (2013). Handedness: A neurogenetic shift of perspective. Neuroscience & Biobehavioral Reviews, 37(10), 2788-2793. doi:10.1016/j.neubiorev.2013.09.014
Scharoun, S. M., & Bryden, P. J. (2014). Hand preference, performance abilities, and hand selection in children. Frontiers in Psychology, 5, 1-15. http://doi.org/10.3389/fpsyg.2014.00082