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Critical Analysis of Left Brain Vs. Right Brain Dominance

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    In pop psychology, references are often made to the supposed differences between left-brained (analytical) and right-brained (creative) people. In reality, the human brain is divided at the longitudinal fissure into two cerebral hemispheres, which are equal in function and nearly identical in structure. Therefore, both sides contribute to all types of human decision making, from the logical to the imaginative. While scientists are still exploring the possibility of modularity in brain development and function, this sample cognitive science essay describes how lateralization studies have yielded no support for the left-versus-right theory in either the female or male brain.    

    Are brain hemispheres lateralized?

    According to science writer Carl Zimmer, the left and right sides work in tandem, regardless of lateralization. While the left hemisphere is more focused on the sounds of word formation, the right side detects intonations and feelings conveyed in a given word (Zimmer).

    For instance, if a woman says to her friend that she "really likes the look of that light-brown, flared, polyester leisure suit with the orange, wide-collar, button-up shirt," the friend will draw upon the left half of his brain to identify the words, but utilize his right hemisphere to determine whether she's being sincere or sarcastic.

    When brain injury occurs, functions of that area can often be taken up by adjacent parts within the same or opposite hemisphere. If pathway damage occurs between one area and another, alternative routes of communication will often pick up the slack, though perhaps not with the utmost efficiency.

    Only if a person undergoes the removal of one cerebral hemisphere or the other might he or she be considered a strictly right or left-brained individual (Goswami).

    One function in which lateralization is most evident is the matter of right-handedness versus left-handedness, which often correlates to opposite-hemisphere dominance. For instance, the vast majority (95 percent) of right-handed people have language dominance in the left hemisphere, though only 18.8 percent of left-handed people have things wired the other way around; a further 19.8 percent of lefties have language functions on both sides (Taylor and Taylor).

    How lateralization was discovered 

    In 1861, French surgeon Pierre Paul Broca made one of the earliest discoveries of brain lateralization while examining the brain of a speech-impaired male, who was nicknamed after the only word he could pronounce: "tan." It was found that the patient—who suffered aphasia—had a syphilitic lesion in the speech-making frontal lobe of his left cerebral hemisphere; a condition subsequently termed "expressive aphasia."

    Later that century, German physician Karl Wernicke explored the possible correlation to brain health and linguistic deficits. Through examinations of the left posterior, he found that language problems were caused by superior temporal gyrus. Wernicke coined the phrase "receptive aphasia" to describe this syndrome. 

    Though seminal, the studies of Broca and Wernicke were done on the brains of live and dead subjects, which raised concerns about the safety of such research. Over the next century, however, advances in technology allowed physicians to study patients brains via magnetic resonance imaging (MRI) and positron emission tomography (PET), where images are captured noninvasively to study, diagnose, and treat conditions of the brain and other areas of the body.

    Brain mapping

    The 1940s witnessed the development of brain mapping, which helped lower the possibility of side effects during brain surgery. The technique was developed by neurosurgeon Wilder Penfield and neurologist Herbert Jasper, who used electrical currents to stimulate parts of the motor and sensory cortices of the brain. Through these tests, they discovered that stimulation on one side of the brain triggers reactions on the other half of the body. 

    Patients with severe epilepsy

    In the 1960s, researchers Michael Gazzaniga and Roger Wolcott Sperry conducted studies on patients suffering severe epilepsy, in which the two halves of the brain fail to communicate due to a split in the corpus callosum. Upon examining different cognitive processes in affected individuals, it was found that the brain's right side was capable of minor language formation, but without any sense of grammar (Kandel et al.)

    Hemisphere specialization: What each side does best

    The two areas of the brain linked to speech—the frontal dominant hemisphere (Broca's area) and the superior temporal gyrus (Wernick's area)—are connected by a tract of white matter known as the arcuate fasciculus, which coordinates neurons in both areas in the co-formation of language. When it comes to language functions, prosodic parts of speech (stress, tone, intonation) are usually lateralized on the brain's right side.

    The left side, however, accounts for all other language functions (grammar, meaning) in nine out of 10 right-handed individuals; as well as some lefties, many of whom are bilateral.

    In most individuals, the processes of visualization, hearing, creativity, and perception are largely bilateral, though believed by some to be stronger on the right half of the brain (Beaumont). The right hemisphere is more readily linked with depressive thoughts, such as pessimism, sorrow, and self-deprecation. By contrast, the left side is often linked to positive mental processes such as enjoyment and decisiveness. Unique and unusual experiences are processed more on the right half of the brain, while predicted and planned situations tend to be handled on the left.

    Lateralization in other species

    In the non-human brain, hemisphere specialization is also evident among various types of species, for which the left brain deals with routine experiences while the right side handles unexpected situations. The difference between regular activity (nesting, foraging, feeding, burrowing) and escaping dangerous situations (steep hills, big predators) reflects the differences between left and right-hemisphere specialization among animals.

    Comparisons between scientifically lateralized and non-lateralized chicks indicate that lateralization is down to evolutionary necessity. In one study, chicks were lateralized via light exposure to their eggs before hatching. When examined in a lab setting with non-lateralized chicks, both groups performed equally well at picking up pebbles, though the lateralized chicks used only one eye. But when it came to picking up food and looking out for predators simultaneously, the lateralized chicks outperformed their non-lateralized counterparts, who also started to wear out sooner (Rogers).

    Evolution of the left-brain/right-brain theory

    The popular conception of the left-brained/right-brained theory grew out of widespread exaggerations and misunderstandings of the work of Broca, Wernick, Gazzaniga, Sperry, and other pioneers in lateralization research. As a concept, the theory gained traction with the public at large during the last quarter of the 20th century, when common folks began fancying themselves as being either right-brained (creative, subjective, emotional) or left-brained (analytical, objective, stoic).

    Though it was never green-lighted by science, the theory has since become a common theme in lifestyles magazines and on television talk shows. All across the Internet, numerous tests are offered that claim to identify whether a subject is a left or right-brained individual.

    Does hemisphere specialization support the theory?

    When Sperry cut the corpus callosum in patients with severe epilepsy, studies of the now split-brained patients indicated that objects processed in the right hemisphere were unidentifiable, but that objects processed on the left side could easily be identified. When Sperry won the 1981 Nobel Prize in Physiology and Medicine, the theory that speech is thoroughly controlled by the left hemisphere gained popular traction.

    However, subsequent studies would reassert the idea that speech formation is a somewhat bilateral process, despite the left-sided leanings of most right-handed individuals. Further research has indicated that mathematical skills are linked to both halves of the brain. The conclusion today in neuroscience is that the two hemispheres—linked through the corpus callosum—work in coordination with one another on a vast range of functions. 

    In a 2013 lateralization study of 1,000 subjects aged 7–29 at the University of Utah, it was found that both the right and left hemispheres are equally active at processing thoughts and feelings, regardless of whether the activity was slightly higher in certain brain regions among some of the participants (Preidt).

    Why the left-brain/right-brain myth persists

    With the whole left-brained/right-brained theory largely discredited, one might wonder why it still remains a widely favored concept in pop psychology. While a lot of people are likely unaware that the theory has been debunked, others could simply be holding onto the concept in a figurative sense, because they like it as a metaphor for why people behave in certain ways and thrive in specific areas. 

    Linking talents to hemispheres

    The left-brained/right-brained theory holds that the two hemispheres each trigger distinct processes that are linked to specific talents. 

    The left side is commonly thought to be linked to critical thinking, rational mindedness, and objectivity; which therefore makes left-brained people more stoic, pragmatic, and adept in fields like math, science, and technology. In essence, the left side of the brain is associated with qualities that are considered masculine.

    The right side is generally believed to nurture sentimental thinking, emotional mindedness, and subjectivity; which in turn makes right-brained people more intuitive, impulsive, and prone to talents such as acting, art, and poetry. Basically, the right side of the brain is associated with qualities that are considered feminine.

    What can be gained from the theory? 

    Aside from serving as a historical curiosity for students exploring the evolution of brain studies, the left-brained/right-brained theory can get a person thinking about the beneficial qualities associated with each side. This sample was provided by Ultius, a global leader in matching customers with freelance writers. For help with writing essays similar to this one, learn more about the services our writers provide. 

    Works Cited

    Zimmer, Carl. "The Big Similarities & Quirky Differences Between Our Left and Right Brains." Discover Magazine. Kalmbach Publishing Co. 15 April. 2009. Web. 29 Aug. 2015. 

    Goswami , Usha. "Neuroscience and education: from research to practice?" Nature Reviews Neuroscience 7. London: Macmillan Publishers Ltd., 2006. 406-413. Print.

    Taylor, Insep, and M. Martin Taylor. Psycholinguistics: Learning and using Language. Lincolnshire: Anybook Ltd., 1990. 362. Print.

    Kandel, Eric R., James H. Schwartz, and Thomas M. Jessell. Principles of Neural Science, 4th ed. New York: McGraw–Hill, 2000. 1182. Print.

    Beaumont, J. Graham. Introduction to Neuropsychology, Second Edition. New York: The Guilford Press, 2008. Chapter 7. Print.

    Rogers, Lesley J. "Light input and the reversal of functional lateralization in the chicken brain." Behavioural Brain Research. Elsevier: Amsterdam, 1990. 211-221. Print.

    Preidt, Robert. "Study Challenges Theory About Left Brain/Right Brain Behavior." Health Day. 15 Aug. 2013. Web. 29 Aug. 2015.

     
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