The Brain and Lefties: What is the Connection?

            For as long as I could remember, I was just like my elementary and middle school classmates. We played the same games, enjoyed the same songs and laughed at the same jokes but it was not until I walked in the classroom on the first day of high school did I know I was different. My difference did not have to do with my clothes or the kind of backpack I decided to wear that day but simply with the hand I had chosen to write with: my left hand. I scanned the classroom for a left-handed desk, but to no avail. I was forced to sit uncomfortably at a desk fit for a right-handed person, just like I often find myself doing to this day. From then on, I became more aware of the scientific reports claiming that people that write with their left hands thought differently than those who wrote with their right hands by using different sides of the brains, but how?  To my knowledge, everyone’s brain functioned similarly in how they control body temperature, blood pressure, heart rate and breathing and how they are separated into two hemispheres. It was shocking to learn that how a person thinks is simply controlled by what hand he/she writes with, but the real question is how?

            To fully understand why a left-handed person might utilize the right side of their brains and a right-handed person, their left side, it is important to know how the brain works as a whole. The human brain typically weighs 3 lbs and is the source of the cognitive, conscious mind [1] and is made up of three main parts, the cerebrum, cerebellum and the brain stem. The cerebrum is the largest part of the brain and because of its size, it is split up into four lobes: frontal, parietal, occipital and temporal [2]. The frontal lobe is associated with emotion and reasoning, the parietal is associated with movement and perception of stimuli, the occipital lobe is associated with vision and the temporal lobe deals with memory and speech [2]. The second part of the brain, the cerebellum, is associated with balance while the brain stem is responsible for the basic life functions such as breathing [2]. The most interesting thing about the human brain is how although it is seemingly one entity, but in actuality divided into two hemispheres, the left and right hemispheres, respectively. These two hemispheres are linked by a large, bunch of nerves called the corpus callosum [3]. Because of the presence of the corpus callosum, scientists knew that the two hemispheres did not act separately, but instead had very distinctive characteristics.

            The term “brain lateralization” refers to the fact that the two hemispheres of the human brain may look similar but each hemisphere has functional specializations [4] where there are functions whose neural mechanisms are located on a specific hemisphere of the brain. The left hemisphere consists of sequential, analytical and logical functions while the right hemisphere has more holistic and visual functions [3]. Some scientists have proven that both sides of the brain deal with language and mathematics skills but in differing ways. The left hemisphere processes more of the grammar side of learning a language while the right hemisphere deals with understanding the context of a language, in mathematics; the left hemisphere is associated with counting and measuring while the right hemisphere is more associated with shapes and motion [3]. Paul Broca, a French neurobiologist, was the first to make a connection between ones dominant hand- whether it is left or right- to the side of the brain that the person most utilizes [4]. Broca’s original theory was that left-handed people must have a brain that is the mirror image of the brain of right-handed people [5].  Evidence today shows that Broca’s theory was not true that in fact, 95% of right handed people and 75% of left handed people have language processing in the left side of the brain [4][5]. Just in the way that people have a dominant hand, they have a dominant side of the brain in which they use.  According to an article from Associated Content, “handedness is generally the outward manifestation of brain hemisphere dominance” [6] and in the dominant hemisphere is usually opposite the hand that one writes with. In this sense, left handed people use the right hemisphere of the brain in thinking meaning that left handed people are supposed to be more creative and free thinking.  As a leftie myself, I can attest that I lack creativity and that I also tend to think more in a logical and more linear manner, both left brained functions. Could I just be an exception? Maybe so, but could I be one of the many people “who [is] forced to live in a world where linear sequential thinking is the norm and is, in fact, demanded of [me]?” [6].

            For centuries, the left hand has had a negative stigma to it. In many European languages, “right” is the synonym for correctness, justice and authority while the Latin word sinistral, the root for the word sinister, means pertaining to or facing the left or “left” [7].  Only in recent decades has the population of lefties been increasing and now about 10% of Americans are lefties. From studies on the brain, we now know that the left and right hemispheres are responsible for certain functions and because of these studies it is obvious to connect the dominant hand to the opposite, dominant side of the brain. But it is also helpful to think about how a society in which a leftie might live in can affect how he/she thinks by enabling that person to strike a balance between the two sides of the brain. Although there is a dominant side of the brain that people use to think, “ the personality that wins out is the one that is associated with the dominant hemisphere but the other is always lurking” [6]. This concept is something worth thinking about, and the side of the brain you use is ultimately up to you. 

[1] http://en.wikipedia.org/wiki/Human_brain

[2] http://serendip.brynmawr.edu/bb/kinser/Structure1.html

[3] http://en.wikipedia.org/wiki/Cerebral_hemispheres

[4] http://www.indiana.edu/~primate/brain.html

[5] http://www.jstor.org/view/00029556/ap050415/05a00110/2?frame=noframe&userID=a56ad1a7@brynmawr.edu/01c054500a0050b907&dpi=3&config=jstor

[6] http://www.associatedcontent.com/article/275061/in_two_minds_left_and_right_handed.html

[7] http://en.wikipedia.org/wiki/Left-handed