The Brain and Lefties: What is the Connection?

Kendra's picture

            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



Comments

Renu Mann's picture

asymmetry indeed

I'm left-handed too, and this article piqued some thoughts:

Never depressed, but I can agree to the 'lost' aura that surrounds me when I'm mentally caged (during long periods of stress, eg. exams) -there is a visual stress syndrome called the Irlen Syndrome, claiming modified biochemical processes in the eye and associated pathway. Theoretically for these people, "inappropriate light", photons in a particular wavelength, can alter brain perception and can continue overtime, simply unknowingly (environmental factor).

Perhaps this is contributed by Psychovisual Linear Light, that can alter image brightness. This light has a low chroma value (close to white light), something like when you're blinded by the sun. Now consider the opposite, like prolonged exposure to darkness and activation of rods in the eye. Low intensity light (night vision) causes greater sensitivity in rod photoreceptors, so nocturnalism or night owls could be affecting biochemical pathways?

“[Irlen Syndrome] is more prevalent in people who suffer from fluorescent light-sensitive migraines. My research also indicates that people with a familial history of migraine and left-handed people are more prone to it.”

Could it be that the reason left-handed people are more 'hollistic' is the same reason there is more sensitivity to certain light in Irlen Syndrome? Only the pineal gland detects material impulse of light and from here it enters your conscience mind to form an image. This gland is the sole combination brain structure (controlling both left and right), located on the midline.

Reminds me of circadian hormones, where light restriction could cause melatonin inhibition or confusion, triggering light sensitivities. Melatonin is converted from serotonin (linked to depression) in the pineal gland. From here we get into the fun stuff, like lucid dreams (induced by writing down dreams upon waking, if you still remember them), DMT (produced by the pineal gland as well), m-state elements, delta wave deep meditation, and emotion control which is linked to this area.

If left-handedness in extreme assumption and simplification, affects (but is not limited to) visual perception perhaps through hypersensitive rods (horizontal cell involvement?), one can try and unearth the connection between it, and specifically, right-sided pineal functions. Imaginably, done by using research from several neurological disorders (including Irlen's) which are more frequent in left-handed individuals in comparison to the general population.

I thoroughly entertain the idea of what Descartes believed, "seat of the soul". Cheers!

Javed mahetar's picture

Your Article

The thing you have discribed sounds good in my right hemisphere but have you ever think that it's not your left hand the thinks but actually brain.

Serendip Visitor's picture

left handed

Interesting read.

I'm a left hander myself. I use my left hand for certain things (writing, holding knifes and forks etc) yet use my right hand for other things such as throwing a ball and holding a bat. I also snowboard left-footed yet kick a ball right footed. So I'm sort of mixed up haha.

I'm right brain dominant, as growing up I was always really into art and drawing. And to this day I create my own music. I just feel that creating is something that I have to do as it makes me feel content and without it I end up feeling really unsettled and I almost get a 'lost' feeling and can get depressed.

The funny thing however is that I'm still very much a logical person, and posses alot of the 'left brained' traits too. I'm actually studying engineering at university aswell. The one thing I've noticed though is that I have a very different style of learning compared to the others in my course. The others can look at a math equation and understand it. I generally find I have to visualize it to understand it. I also sometimes have abstract approaches to things, that don't always seem to make any logical sense, but somehow end up being right / who end up working for me.

Agnes  Scott's picture

I have many question as a left handed person .

I'm left handed,I read and play music,write poetry
just wrote my first play. I fine that it is very hard to relax
however I make my self, my mind is going all the time, I dream
when I sleep,and things I dream come true. some times I write
them down . I have been told I have a gift for seeing things
before they happen. been that way from a child.
I was
a foster child from the age of two that I can remember.
when I was 12 years old I saw a vision of a white robe trimed
In gold at the foot of my bed, with a white light around it
so bright it was almost blinding. I use to pray for God
to take this Grift away from me. Now I except it have for many
years being left hand In a right handed world, is deep.

A. Scott

Paul Grobstein's picture

diversity, handedness, and the brain

It is indeed worth noticing that handedness is one of the (many) ways humans differ from one another. And that there is a brain "handedness" (assymetry) as well (probably lots of them). The two sometimes correlate but sometimes don't. So maybe there is still more human diversity? Maybe its missed in the interests of "linear sequential thinking"? Are there really good observations suggesting that the percentage of left handers is increasing? If so, an instance of human evolution in progress?

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