Ambidextrous Brains: How Handedness Affects the Brain

 

Being truly ambidextrous means that an individual is able to use both their right and left hand equally well. The ability to do simple tasks such as throwing a ball, signing a check, or buttoning a shirt with either hand could save time. While this may sound advantageous, being ambidextrous can actually inhibit specialization of the brain. Keep reading below as Jacquelyn Brown explains how this perceived advantage may actually be a complication.

ambidextrous

Ambidextrous

Right-Handed World

I have a very distinct childhood memory of being more or less forced to be right handed. I was coloring at my kitchen table and holding a crayon in my left hand, my mother walked into the room and simply took the crayon from my left hand and placed it on my right. She then encouraged me to continue coloring. This type of behavior was continually encouraged as I began to learn to write my name, and all though my grade school career.

ambidextrous

Ambidextrous

Forced Right-Handedness

Although I still hold a small grudge against my mother and my early grade school teachers, being forced to be right-handed has not negatively impacted my life. Forced righties, like myself, were not developmentally behind or subjected to playing any “brain catch-up” early in childhood. This is because of the brain’s plasticity.

Neuroplasticity is your brain’s amazing ability to alter its synapses and pathways through environmental and behavioral experiences. When you are a child, your brain has a high affinity for change, and thus certain biological predispositions can be more easily altered. So, when my mom took the crayon out of my left hand and placed it on my right, she was encouraging a change in my behavior. My brain recognized this was able to strengthen synapses associated with right-hand motor movements as I repeated this behavior. Natural righties would have experienced this synaptic strengthening similarly, the only difference is that they already had an innate preference to use their right hand.

My personal anecdote is not uncommon. We live in a right handed world, and I’m sure my mother was just trying to assimilate me into it. In fact, many righty-converted children still use their left hands for important tasks. For instance, many innate tasks such as feeding one’s self are often still done by the left hand. How a young child plays can also be telling of their hand preference. Personally, I noticed that when I hula hoop my hoop swings to the right (clockwise), whereas my friends, who are naturally righties, all swing their hoops to the left (counter-clockwise). This behavior is not something that would be actively monitored, or even noticed, by a parent or teacher trying to persuade right-handedness.

These innate and behavioral preferences for a left-handedness cannot be confused for being ambidextrous, but rather it is referred to as being “mixed handed.”

Mixed Handedness is Not Ambidexterity

ambidextrous

ambidextrous

Mixed handedness is seen in more individuals than just converted lefties. Most people who play an instrument such as guitar, piano, or percussion are proficiently mixed-handed. This is almost always only observed in tasks that mimic motor skills that would be used while playing an instrument.

In these specific instrumental examples, each hand is learning a separate set of skills, and often, the non-dominant hand is playing dexterity catch up. This is also why skills unrelated to the instrument are still more difficult to perform with the non-dominant hand. Think about the process the brain must go through to inhibit the use of what the brain sees as the dominant hand, and then train the non-dominant hand to do its job. While over time this process becomes almost automatic, it still has to use more energy than just using the dominant hand. Essentially, the brain needs the context of playing the instrument in order to perform a mixed-handed behavior.

Various studies have been done on how beneficial playing an instrument is for your brain. That being said, how different is mixed handedness versus being ambidextrous? What about this difference could potentially make ambidexterity disadvantageous?

The reasoning lies in the structure of your brain and the functions of its hemispheres.

Two Brains Inside Your Head?

The brain has two hemispheres, that each specialize to govern specific tasks. The right hemisphere of the brain controls the left side of the body, and is associated with mainly spatial perception tasks, face recognition, and understanding music. The left hemisphere controls the right side of the body, and is associated with more computational tasks such as math and logic. The specialization of each side of the brain is important because it allows for maximizing neural processing.

Handedness can correlate to what function each hemisphere specializes in, which allows the brain to be almost anatomically symmetrical, but functionally asymmetrical. Functional asymmetry, or lateralization, allows for each hemisphere to work in tandem when processing the world around us.

Language Lateralization

One of the best examples of brain lateralization is language. Both hemispheres are used in language processing and production, but not to the same degree. Most commonly, when referring to language lateralization, two important brain regions are noted. These two regions are Broca’s area and Wernicke’s area. Broca’s brain area that is involved in producing speech, whereas Wernicke’s area is involved in comprehension of speech. Activity in these areas of the brain are also associate with the production and comprehension of written language as well.

ambidextrous

ambidextrous

As mentioned before, the brain is almost anatomically symmetrical, so each hemisphere has the anatomical ability to compartmentalize language into the regions described as Broca’s and Wernicke’s areas. Due to this, after lateralization occurs through development, the hemisphere that did not specialize has subsequent association cortexes. These areas are found at the anatomical mirror image, but do not function identically. Instead, they are described to “color” language.

Coloring language is essentially the nuances, tone of voice, and emotion that is conveyed by speaking. The association area related to Wernicke’s area would be able to detect the emotion and tone of voice in someone else’s speech, and production of emotion and tone of voice would be governed by the associated area to Broca’s area.

Want to read more about different parts of the brain?

Alright, this may seem interesting, but how is it related to handedness?  As previous described, there is a correlation between handedness and hemisphere lateralization. Staying with the language example, it has been observed that language is almost always held in the left hemisphere, accounting that roughly 90% of the world’s population is right handed, it seems that this is a strong correlation. Inversely, left handedness and right hemisphere language lateralization is observed, but not in every case.

Ambidextrous Brains and Disorders

Being truly ambidextrous could be most easily observed as the identical nature of motor patterns used when writing. These patterns would more than likely be equally as strong. You would think that more connections and stronger connections between various areas of the brain would be a good thing, right? Unfortunately, no.

As each hand is competent at performing the same tasks to the same quality level, this makes the brain more symmetrical; as proven by the little differentiation between hemispheres seen in brain scans of ambidextrous individuals. This lack of asymmetry is tied to heightened risk of ADHD, language problems, and subsequently poor performance in school.

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ambidextrous

Ambidextrous

These varying difficulties are hypothesized to be due to the brain’s hemispheres competing with each other. Scholastic tasks, such as reading and writing, which are associated with Wernicke’s and Broca’s areas, are learned more slowly. This is because both sides of the brain are being fed the same sensory information. One hemisphere is not permitted to continue to develop and surpass the other in this specific area. Thus, these degrees of lateralization are unable to occur. Language, facial recognition, and other visual skills are being competitively processed as well, but nuances of these tasks suffer.

Differentiation of the hemispheres is more common, and evolutionarily successful due to the low percentage of ambidextrous people compared to right handed individuals. This percentage breaks down into 90% of the population being right handed, 9% being left handed, and only 1% being truly ambidextrous. This concludes that being ambidextrous is not evolutionarily advantageous. Persistence of this favor for handed dominance correlation with brain lateralization is an important aspect of understanding handedness. Specialization of the hemispheres is what the brain is programmed to do, and not allowing for that to take place is a key factor in understanding ambidextrous cases of atypical brain behavior.

Do you have any questions? Leave me a comment below! 🙂

Jacquelyn is currently an undergraduate student at the University of Pittsburgh. She is studying both Neuroscience and Psychology, and earning a minor in Chemistry. Jacquelyn is particularly interested in neuromuscular research and neurobiological diseases related to aging, and hopes to apply her passions to future functional neuroscience research.