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Can drawing a duck define a person's hemispheric dominance?

Can drawing a duck define a person's hemispheric dominance?



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When I was on 7th grade, our math teacher asked every one of us to draw a duck. In the class of 34 students, a large portion of the students drew a left-facing duck.

The teacher said that it's a simple test to figure out if a person is either right or left-brain dominant. So the people who drew a duck facing to left is a right-brainer, and vice versa. Apparently this Duck-test was quite popular in middle school.

Some even say, people who often draw a duck who faces left side is a left brain (instead of right). Although some says it's just muscle memory/ tendency.

My question is- is this mini test legit? Can you get a glimpse of someone's brain dominance by drawing a duck?


What is the dominant hemisphere in the first place? I found the following definition (source: Medical Dictionary):

[The] dominant hemisphere [is] [t]he left half of the brain in almost all right-handed people and 85% of left-handed people. This is the hemisphere concerned with language and logical thought and containing the motor areas for voluntary use of the right side of the body. In 15% of left-handed people, the right hemisphere is dominant and subserves speech.

Now, your ducks facing left or right hardly seem to reflect either language, logic, motor lateralization or handedness. Instead, often questionnaires or inventories are used, for example to tease out whether a person is logical, rational and verbal (left-sided); or emotional, manipulative/spatial and creative (right-sided). However, the meaning, relevance, and possible use of hemispheric dominance is debated.

Note that brain lateralization is certainly true for a number of functions, including speech and motor control, but the more dramatic examples of brain lateralization should be interpreted with caution, and I quote from Corballis (1980):

Since ancient times, right and left have been associated with different fundamental classifications, including male and female, good and evil, day and night, straight and crooked. [… ] Interpretations of cerebral asymmetry that emphasize a fundamental duality in cognitive processing between the two sides of the brain, or that locate consciousness in the left side only, are probably modern manifestations of the age-old mythology of left and right.

Reference
- Corballis, American Psychologist (1980); 35(3): 284-95


What Is the Theory of Right Brain Left Brain?

The concept of right brain and left brain thinking developed from the research in the late 1960s of an American psychobiologist Roger W. Sperry. He discovered that the human brain has two very different ways of thinking.

  • The right brain is visual and processes information in an intuitive and simultaneous way. It looks first at the whole picture and then the details.
  • The left brain is verbal and processes information in an analytical and sequential way. It looks first at the pieces and then puts them together to get the whole.

Sperry was awarded a Nobel Prize in 1981 for his research. As fun as the right brain left brain theory is to think about, it has since been labeled as one of the great myths of the brain. In reality, both hemispheres of our brain work together for a variety of tasks, including creative and logical thinking.


Handedness: What Does It Say About Your Brain Structure?

Left-handedness, as a relatively uncommon phenomenon, never fails to fascinate people. There is a common perception that left-handed people are more talented and artistic. To what extent these assumptions are correct, and what your preferred use of right or left hand can tell you about your brain structure?

Handedness represents the better performance or preference of using one hand, i.e., the dominant hand. Right-handedness is the most common type observed in 70–95% of the world population, followed by left-handedness, and then a very rare type of mixed handedness and ambidexterity. Although this is an important physiological feature in humans, it seems that the origins of handedness are not well understood.

While many scientists assume that genetics is the main determinant of handedness, others disagree and believe that other factors also play an important role. They believe that variations in handedness are related to some behavioral and anatomical measures. For instance, although just 10% of humans are left-handed, these individuals tend to be over-represented in artistic professions, have better mathematical abilities, and have a lower predisposition to diseases such as arthritis and ulcers. On the other hand, there is an increased prevalence of some health issues, including cardiovascular disease, dyslexia, asthma, multiple sclerosis, and others.

In addition to strict (constant) handedness, there is something called mixed, i.e., inconsistent handedness. Some scientists believe that mixed-handed individuals are of poorer mental and physical health, with lower cognitive parameters and higher rates of dyslexia and attention deficit hyperactivity disorder (ADHD). Mixed-handedness (a change in hand preference depending on the task) has been associated with greater atrophy of the hippocampus and amygdala, brain structures that are strongly associated with dementia and cognitive aging. Also, non-right handers (mixed or left-handed) are at higher risk of neurodevelopmental disorders, including autism, epilepsy, and schizophrenia.

Handedness reflects the structure of our brain, more specifically its asymmetry. The functional differences in the right and left brain hemispheres are believed to underline the phenomenon of hand dominance. Handedness is probably the most obvious manifestation of the fact that our brain functions in an asymmetric manner. While the left hemisphere controls right-handedness, i.e., the dominant right hand, the right hemisphere controls dominant left-handedness. The left hemisphere is also specialized for language and logic in most people, while right hemisphere specialization is related to intuition and creativity. Asymmetry of the brain and handedness become detectable very early, even during fetal development. Ultrasound examinations have revealed that even at the 10 th week of gestation, most fetuses move their right arm more often than the left one, while from the 15 th week the majority of fetuses suck the right thumb. This is believed to be predictive of future handedness. In line with this is the leftward enlargement of brain structure (seen in the first trimester of pregnancy), which plays an important role in neurological development.

Studies have linked handedness with differences observed in language lateralization. More precisely, right-handed individuals are characterized by left hemisphere control of language, while left-handers have shown right hemisphere dominance in language or bilateral speech representation. One interesting study questioned whether early childhood handedness can influence language development. The authors assessed the handedness of infants aged 6 to 18 months at each month and then again when they were toddlers (from 18 to 24 months). They found that constant use of the right hand during infancy was associated with having superior (advanced) language skills at 24 months old. On the other side, children who were not lateralized in infancy and became right or left handed as toddlers had the average expected language scores for their age.

There are also differences in the lateralization of visual areas of the brain between right and left-handed individuals. In right-handers, there is much higher activation of the right fusiform face area (the area responsible for face visualization) and the extrastriate body area (responsible for body visualization). Meanwhile, in left-handers, these areas are equally activated across both brain hemispheres.

Some researchers believe that brain volume may correlate with handedness, although the data on this subject remains controversial. One group of researchers reported that left-handed individuals had a larger brain, while another study found no difference in brain size between the right- and left-handers. As some findings indicate, left-handers are more prone to nighttime awakenings due to sleep disorders caused by periodic limb movements. It seems that left-handed individuals are more likely to experience limb movements while asleep compared to right-handers.

Since handedness has been associated with prenatal hormonal exposure, it could influence the risk of carcinogenesis later in life. Scientists investigated the impact of handedness on brain tumors, both malignant and benign ones. One study examined the associations between glioma, meningioma, and acoustic neuroma with self-reported handedness. Left-handers or ambidextrous (with equal use of both hands) individuals were at reduced risk of glioma (the most common malignant brain tumor) when compared with the right-handers. This relationship was similar for both genders. However, another very recent study found no such association. This large case-control study (which included more than 1000 glioma cases and healthy controls) reported no association between handedness and glioma risk after adjustment for age, gender, and race.

Although the brains of left-handers and right-handers differ in their structures, the available literature shows no noteworthy differences in intelligence as measured by IQ score. Nevertheless, these brain structure differences seem to reflect the more diverse and creative processing of language and emotions by left-handers than by right-handed individuals. This may explain why a greater proportion of left-handers are professional musicians, even in those cases when the musical instruments are designed for right-handers (for example, violins). Similarly, the gift for mathematics seems to be more common in the left-handed populace.

It is obvious that right and left-handers differ not only in hand preference but also in brain structure. This further reflects the ability to perform different tasks and achieve success in different professions. Although there is a clear link between non-right handedness and developmental disorders, there is no association between brain carcinogenesis and the dominance of one hand. It seems that handedness can be predicted in early childhood, even during fetal development, but further investigations are needed to elucidate the origins of our preference to use one hand or the other.

Cherbuin, N., Sachdev, P.S., Anstey, K.J. (2011). Mixed-handedness is associated with greater age-related decline in volumes of the hippocampus and amygdala: the PATH through life study. Brain and Behavior. 1(2): 125-134. doi:10.1002/brb3.24

Corballis, M.C. (2014). Left brain, right brain: facts and fantasies. PLoS Biology. 12(1):e1001767. doi:10.1371/journal.pbio.1001767

Nelson, E.L., Campbell, J.M., Michel, G.F. (2014). Early handedness in infancy predicts language ability in toddlers. Developmental Psychology. 50(3): 809-814. doi:10.1037/a0033803

Li, M., Wang, J., Liu, F., Chen, H., Lu, F., Wu, G., Yu, C., Chen, H. (2015). Handedness- and brain size-related efficiency differences in small-world brain networks: a resting-state functional magnetic resonance imaging study. Brain Connectivity. 5(4): 259-265. doi:10.1089/brain.2014.0291


Right-Brain Hemisphere

The hemisphere of the brain that neurologically controls the left side of the body and is thought to control spatial tasks, musical and artistic endeavors, body control and awareness, and creativity and imagination.

In normal human adults, each hemisphere of the brain, working in concert with the other, performs certain types of functions more efficiently than the other. While the left-brain hemisphere is dominant in the areas of language and logic, the right-brain hemisphere is the center of nonverbal, intuitive, holistic modes of thinking. Each hemisphere mostly receives perceptions from and controls the activities of the opposite side of the body. Scientists have been aware of the specialized functioning of the hemispheres&mdashalso known as lateralization&mdashfor over one hundred years, having discovered that language skills are controlled by the left side of the brain in approximately 95 percent of right-handed people and about two thirds of left-handed individuals. In the nineteenth century, however, this discovery led to the assumption that all higher reasoning ability resided in the left-brain hemisphere, which was thus regarded as dominant overall. The right brain hemisphere was thought to possess only lower-level capabilities and was considered subordinate to the left.

Research conducted in the 1950s and 1960s established that the two hemispheres of a normally functioning brain&mdashconnected by the corpus callosum, a thick cable of nerves&mdashoperate in a complementary fashion with both hemispheres involved in higher cognitive functioning. The primary difference between them was found to involve the mode rather than the level of thinking. A research group under the direction of Roger Sperry at the California Institute of Technology observed and tested patients who had undergone a surgical procedure in which the corpus callosumwas severed to control epileptic seizures. In this procedure, the two hemispheres of the brain, which normally have a strong tendency to work together, were uncoupled, and each side of the brain remained ignorant of information received by the other. Thus, right-handed people had no trouble writing, which is usually governed by the left-brain hemisphere in righthanders, but were unable to draw, as the left brain was cut off from the spatial capacity of the right. When a special apparatus was used to present the image of a spoon only to a split-brain patient's left hemisphere, the subject could name it readily, but when the same image was presented to the right-brain hemisphere, the subject could not, although they were still aware of what it was.

Research on both split-brain and normal subjects since the 1960s has confirmed that both hemispheres of the brain use high-level cognitive modes. That of the left brain is verbal and analytic, while right brain thought processes are rapid, complex, whole-pattern, spatial, and specialized for visualimagery and musical ability. The right temporal lobe, in particular, governs visual and auditory imagery. People in whom this area is damaged have difficulty recognizing familiar melodies, faces, and pictures, and learning to identify new ones. The right brain hemisphere also appears to have special links to emotion. Right-brain damage interferes with both the ability to produce and interpret expressions of emotion. Damage to the front part of the right-brain hemisphere renders people unable to act on or express strong emotions. If the damage is further back in the brain, the person can express emotion but not recognize it in other people or in pictures.

Other general characteristics of right-brain thought processes include the tendency to synthesize rather than analyze, and to relate to things in a concrete rather than a symbolic fashion. Where left-brain thinking tends to represent wholes by abstraction (using one piece of information to represent something larger), the right brain is more likely to interpret data through analogies ó &mdashseeing relationships between wholes. Right-brain functioning is nontemporal, nonrational, holistic, and intuitive, relying on leaps of insight, hunches, or visual images. Discoveries about the right- and left-brain hemispheres have led some researchers and educators to advocate educational reforms that would allow right-brain modes of thought a greater place in the current educational system, which reflects society's overall tendency to reward the verbal, analytical left-brain skills. As split-brain researcher Roger Sperry notes, our educational system "tends to neglect the nonverbal form of intellect. What it comes down to is that modern society discriminates against the right hemisphere." The artistic, creative right brain is relegated to the "minor" subjects of art and music, but the main programs of study do not, as a rule, focus on developing the right-brain skills of imagination, creativity, or visualization.


Psycholinguistics/Hemispheric Lateralization of Language

Hemispheric lateralization refers to the distinction between functions of the right and left hemispheres of the brain. If one hemisphere is more heavily involved in a specific function, it is often referred to as being dominant (Bear et al., 2007). Lateralization is of interest with regards to language, as it is believed that language is a heavily lateralized function: certain aspects of language are found to be localized in the left hemisphere, while others are found in the right, with the left hemisphere most often dominant. This was initially proposed by early lesion-deficit models and studies with split-brain patients, and has been shown in more recent years through tests like the Wada test and imaging studies. There have been studies which show that there are anatomic asymmetries located near and around the regions associated with language, and each hemisphere has shown to play its own but separate role in the production and comprehension of speech. The hemispheric lateralization of language functions has been suggested to be associated with both handedness, sex, bilingualism, sign-language, and a variance amongst cultures. It has also been proposed that a reorganization occurs following brain injury that involves a shifting of lateralized function, as long as the injury occurs early in life.

Jean Baptiste Bouillaud and Simon Alexandre Ernest Aubertin Edit

French physician Jean Baptiste Bouillaud (1796-1881) was one of the earliest proponents of hemispheric language lateralization. On February 21, 1825, Bouillaud presented a paper to the Royal Academy of Medicine in France which suggested that, because so many human tasks are performed using the right hand (such as writing), the left hemisphere might be the in control of that hand. This observation implies that language, at the core of writing, would be localized in the left hemisphere. It was already known at this time that motor function was primarily controlled by the hemisphere ipsilateral to the side of the body through lesion studies. Bouillaud also proposed that speech is localized in the frontal lobes, a theory that was carried on by Bouillaud’s son-in-law Simon Alexandre Ernest Aubertin (1825-1893), who went on to work with famed French neurologist Paul Broca in 1861. Together, Aubertin and Broca examined a patient with a left frontal lobe lesion who had lost nearly all ability to speak this case and several others similar to it became the basis behind the earliest theories of language lateralization.

Paul Broca Edit

French neurologist Paul Broca (1824-1880) is often credited as being the first to expound upon this theory of language lateralization. In 1861, a 51-year-old patient named Leborgne came to Broca Leborgne was almost completely unable to speak and suffered from cellulitis of the right leg. Leborgne was able to comprehend language but was mostly unable to produce it. He responded to almost everything with the word “tan” and thus came to be known as Tan. Broca theorized that Tan must have a lesion of the left frontal lobe, and this theory was confirmed in autopsy when Tan died later that year (Bear et al., 2007). In 1863, Broca published a paper in which he described eight cases of patients with damage to the left frontal lobe, all of whom had lost their ability to produce language, and included evidence of right frontal lesions having little effect on articulate speech (Bear et al., 2007). These findings led Broca to propose, in 1864, that the expression of language is controlled by a specific hemisphere, most often the left (Bear et al., 2007). “On parle avec hemisphere gauche,” Broca concluded (Purves et al., 2008)- we speak with the left hemisphere.

Carl Wernicke Edit

German anatomist Carl Wernicke (1848-1904) is also known as an early supporter of the theory of language lateralization. In 1874, Wernicke found an area in the temporal lobe of the left hemisphere, distinct from that which Broca had described, which disrupted language capabilities (Bear et al., 2007). He then went on to provide the earliest map of left hemisphere language organization and processing.

Lesion Studies Edit

A good deal of what we know about language lateralization comes from studying the loss of language abilities following brain injury (Bear et al., 2007). Aphasia, the partial or complete loss of language abilities occurring after brain damage, is the source of much of the information on this subject (Bear et al., 2007). As shown in the studies of Bouillaud, Aubertin, Broca and Wernicke described above, lesion studies combined with autopsy reports can tell us a a lot about the localization of language, which ultimately has supplied information on lateralization. Lesion studies have shown that, not only is the left cerebral hemisphere most often dominant for language, but also that the right hemisphere generally is not, as lesions in the right hemisphere rarely disturb speech and language function (Bear et al., 2007).

The dangers of using lesion studies are, of course, that they may overemphasize the relevance of particular localized areas and their associated functions. The connection between brain regions and behaviours is not always simple, and is often based on a larger network of connections. This is shown in the fact that the severity of an individual’s aphasia is often related to the amount of tissue damaged around the lesion itself (Bear et al., 2007). It is also known that there is a difference in the severity of the deficit depending on whether the area was removed surgically, or was caused by stroke. This is the case because strokes affect both the cortex and the subcortical structures this is due to the location of the middle cerebral artery, which supplies blood to the areas associated with language, as well as involvement of the basal ganglia, and is often the cause of stroke. As such, surgically produced lesions tend to have milder effects than those resulting from stroke (Bear et al., 2007).

Split Brain Studies Edit

Studies of patients who have had commissurotomies (split-brain patients) have provided significant information about language lateralization. Commissurotomy is a surgical procedure in which the hemispheres are disconnected by cutting the corpus callosum, the massive bundle of 200 million axons connecting the right and left hemisphere (Bear et al., 2007). Following this procedure, almost all communication between the hemispheres is lost, and each hemisphere then acts independently of the other. What is striking about split-brain patients with regards to the study of language lateralization is that a word may be presented to the right hemisphere of a patient whose left hemisphere is dominant, and when the patient is asked to name the word they will say that nothing is there. This is because, although the right hemisphere “saw” the word, it is the left hemisphere which “speaks.” If that same word is presented to the left hemisphere, the patient is able to verbalize the response (Bear et al., 2007). As such, split-brain patients have presented substantial evidence that language function is generally lateralized in the left hemisphere.

Wada test Edit

The Wada test was created by Juhn Wada at the Montreal Neurological Institute in 1949, and was designed specifically to study lateralization. A fast-acting barbiturate such as sodium amytal is injected into the carotid artery on one side (although current procedures prefer to use a catheter which is inserted into the femoral artery), and is then transported to the cerebral hemisphere on the opposite side. It then serves to anaesthetize that side of the brain for approximately 10 minutes, after which it begins to wear off and the functions which were disrupted by the anaesthetic gradually return, often displaying aphasic errors (Bear et al., 2007 Wada and Rasmussen, 1960). During the time in which the patient is anaesthetized, he or she is assessed on their ability to use language. If the left hemisphere is anaesthetized and is the dominant hemisphere, the patient loses all ability to speak, whereas if the left hemisphere is anaesthetized but the right hemisphere is dominant, the patient will continue to speak throughout the procedure (Bear et al., 2007).

In a study published in 1977, Brenda Milner used the Wada test to demonstrate that 98% of right-handed people and 70% of left-handed people have a dominant left hemisphere with regards to language and speech function. Her results also showed that 2% of right-handed people have a dominant right hemisphere, which is the same percentage of patients that display aphasia following a lesion to the right hemisphere (Branch et al., 1964).

This procedure is also used prior to brain surgery in order to determine the dominant hemisphere, so as to avoid removal of an area associated with speech and language.

Functional transcranial Doppler ultrasonography Edit

Functional transcranial Doppler ultrasonography (fTCD) is a non-invasive method for examining event-related changes in cerebral blood flow velocity in the middle cerebral arteries(Knecht et al., 1998). This technique can reliably assess which hemisphere is dominant and to what extent, which regards to language lateralization. Studies using fTCD have shown a linear relationship between handedness and language (Knecht et al., 2000).

Electrical stimulation, TMS and Imaging Edit

Electrical stimulation was pioneered by Wilder Penfield and his colleagues at the Montreal Neurological Institute in the 1930s, and helped to identify certain lateralized areas associated with speech and language. Electrical stimulation is the application of an electrical current directly to the cortical tissue of a patient who is conscious. Penfield found that stimulating the left frontal or temporal regions of the left hemisphere with an electrical current accelerated the production of speech. He also found that stimulation can cause inhibition in complex functions like language, as applying a current to the areas associated with speech production in the left hemisphere while the patient is engaged in speech serves to disrupt this behaviour (Penfield, 1963). This procedure is performed during surgery while the skull is removed, and as such it is not a commonly used method of assessment.

Transcranial Magnetic Stimulation (TMS) is a non-invasive procedure, often combined in studies with MRI, which has helped to map the regions associated with speech, showing lateralization to be dominant in the left hemisphere. TMS has also shown that, following brain injury, it is more likely that it is the tissue surrounding the lesion that acts in a compensatory way rather than the opposite hemisphere providing compensation. The major drawback of TMS is, of course, the fact that the magnetic stimulation must pass through the scalp, skull, and meninges before stimulating the brain region of choice.

Imaging studies have proven to be incredibly useful in determining lateralization of language abilities. Functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have been able to show the complex circuitry associated with speech and language they have also proven to be consistent with the findings from previous lesion studies, as well as Penfield’s electric stimulation (Bear et al., 2007). There has been some controversy regarding bilateral activation shown in fMRI studies, the reasons unknown, however it has been suggested that perhaps the right hemisphere is involved in aspects of speech that are not measured by such tests as the Wada procedure (Bear et al., 2007). A significant finding is that fMRI results during developmental years show activation during speech and the use of language mainly in the left hemisphere, providing further evidence in support of left hemisphere dominance (Bear et al., 2007).

The perisylvian cortex of the left hemisphere is involved in language production and comprehension, which is why it is often referred to as dominant, or said to "speak" (Ojemann, G. A., 1991 Purves et al., 2008). Roger Sperry and his colleagues’ split-brain studies have shown that the left hemisphere is also responsible for lexical and syntactic language (grammatical rules, sentence structure), writing and speech (Purves at al., 2008). Other aspects of language which are thought to be governed in most people by the left hemisphere include audition of language-related sounds, recognition of letters and words, phonetics and semantics.

The right hemisphere, though generally not dominant in terms of linguistic ability, has its role in the use of language. Split-brain studies present evidence that, despite the right hemisphere having no “speech,” it is still able to understand language through the auditory system. It also has a small amount of reading ability and word recognition. Lesion studies of patients who have right hemisphere lesions show a reduction in verbal fluency and deficits in the understanding and use of prosody. Patients who have had their right hemisphere surgically removed (hemispherectomy) show no aphasia, but do show less obvious deficiencies in areas such as verbal selection and understanding of metaphor. It has thus been concluded that the right hemisphere is most often responsible for the prosodic and emotional elements of speech and language (Purves et al., 2008).

The structural differences between the right and left hemisphere may play a role in the lateralization of language. In the nineteenth century, anatomists observed that the left hemisphere’s Sylvian fissure (lateral sulcus) is longer and less steep than that of the right (Bear et al., 2007). In 1980, Graham Ratcliffe and his colleagues used evidence of this asymmetry of the Sylvian fissure, shown in carotid angiogram, combined with results of Wada testing, and found that individuals with speech regions located in the left hemisphere had a mean difference of 27 degrees in the angle of the blood vessels leaving the posterior end of the Sylvian fissure, while those with language located in the right hemisphere had a mean angle of zero degrees.

] In the 1960s, Norman Geschwind and his colleagues at Harvard Medical School found that the planum temporale, the superior portion of the temporal lobe, is larger in the left hemisphere in almost two thirds of humans (Geschwind & Levitsky, 1968), an observation which was later confirmed with MRI (Bear et al., 2007 Purves et al., 2008). This asymmetry exists even in the brain of the human fetus (Bear et al., 2007). The correlation of this asymmetry with the left hemisphere’s language dominance is refuted by many due to the fact that 67% of people show this structural asymmetry, while 97% show left hemispheric dominance. Another problem which exists in examining asymmetry of the planum temporale is how the anterior and posterior borders of this region are defined, and the fact that investigators differ in this definition. This is especially a problem when the transverse gyrus of Heschl, used to mark the anterior of the planum temporale, appear in double (which is not unusual). There are differing opinions as to whether or not the second transverse gyrus should be defined as being within the planum temporale, or outside of it (Beardon, A. A., 1997).

Handedness Edit

The correlation between handedness and hemispheric lateralization is described in the results of the Wada test, described above. The majority of the population is right handed (approximately 90%), and the Wada test results propose that 93% of people’s left hemisphere is dominant for language (Bear et al., 2007). A linear relationship between handedness and langage has been shown using fTCD in a study done by Knecht et al. (2008) their findings show an 27% incidence for right hemisphere dominance in their group of left-handers, a finding consistent with the notion of there being a linear relationship between handedness and incidence of right hemisphere dominance in left-handers (Knecht et al., 2000). This study used a word generation task, and admits that perhaps a measurement of prosody or other such suspected right hemisphere functions may have a different relationship with handedness (Knecht et al., 2000). It is also true that correlation does not necessarily imply causation, and it is also suggested that there is no direct relationship between handedness and language at all, as the majority of left-handers also have their language lateralized in the left hemisphere (Purves et al., 2008). It is, however, a physical example of functional asymmetry, and it is certainly possible that a more substantial connection between handedness and language will be found.

Gender Differences Edit

The tendency for women to score higher than men on language-related tasks is perhaps the result of the fact that women also tend to have a larger corpus callosum than men, indicating more neural connections between the right and left hemispheres. fMRI studies show that women have more bilateral activation than men when performing rhyming tasks, and PET studies show that women have more bilateral activation than men during reading tasks. Perhaps the bilateral activation implies the use of what are thought to be right hemisphere language abilities, such as prosody and intonation. Research has also shown that women have a greater ability to recover from left hemisphere brain damage the evidence provided by the imaging studies in combination with the results of recovery following injury have led to the controversial suggestion that language is more unilateral in men than in women.

Sign Language and Bilingualism Edit

Sign language has shown to be lateralized in the left hemisphere of the brain, in the left frontal and temporal lobes. This is known through the use of lesion studies, in which the patients had left hemisphere lesions in the areas associated with language which impaired their ability to sign, while right hemisphere lesions in the same areas show no linguistic deficit (Hickock et al., 1998). Lesions in the right hemisphere of signers did, however, show a limited use of spatial information encoded iconically (which is when the sign is similar-looking to its referent). This is in keeping with the belief that visuo-spatial ability is a right hemisphere function and suggests that the role of the right hemisphere in sign language is in the non-linguistic features of sign language.

Bilingualism is thought to be an overlapping of populations of neurons corresponding to each language, all of which are located in the frontal and temporal regions of the left hemisphere associated with speech comprehension and speech production.

Culture and Language Lateralization Edit

When thinking of language there is a tendency to focus on that language in which you think, however it has been proposed that lateralization of language functions can vary from culture to culture. Asian languages show more bilateral activation during speech than European languages, likely because Asian languages employ a far greater use of right hemisphere abilities, for example prosody, and the use of spatial processing for the more “pictorial” Chinese characters Native American languages also show a good deal of bilateral activity.

Studies have been done following brain injury to determine the level of recovery of language and speech ability, and whether or not recovery is based on lateralized function. Bryan Woods and Hans-Leukas Teuber looked at patients with prenatal and early postnatal brain injury located in either the right or left hemisphere and drew several conclusions. First, if the injury occurs very early, language ability may survive even after left hemisphere brain damage. Second, they found that an appropriation of language regions by the right hemisphere is responsible for the survival of these abilities, but because of this there is a tendency for visuo-spatial ability to be diminished. Third, right hemisphere lesions have the same effect in prenatal and early postnatal patients as they do in adults. Brenda Milner and Ted Rasmussen used the Wada test to determine that early brain injury can cause either left, right or bilateral speech dominance, and that those who retained left hemisphere dominance had damage that was not in either the anterior (Broca’s) or posterior (Wernicke’s) speech zone. Those whose dominance shifted to the right hemisphere most often had damage to these areas. Milner and Rasmussen also found that brain damage which occurs after the age of 5 does not cause a shift in lateralization but rather reorganizes within the hemisphere, potentially employing surrounding areas to take responsibility for some aspects of speech.

In patients who have had hemispherectomy of the left hemisphere, the right hemisphere can often gain considerable language ability. When performed in adulthood, speech comprehension is usually retained (though speech production suffers severe deficits) reading capability is small, and there is usually no writing capability at all.

1. In terms of hemispheric lateralization and split-brain patients (individuals which have had commissurotomies), if the word “pencil” was presented to the right field of vision of a split-brain patient and he/she was asked to report what they had seen, the patient would respond:

a) by selecting a pencil with the contralateral hand b) by saying the word “pencil” c) by saying “nothing is there” d) by selecting a pencil with the ipsilateral hand

2. The left hemisphere is responsible for all aspects of syntax, except parsing. True or false?

3. What is the structural evidence given to explain the fact that women tend to score higher than men on language-related tasks? What implications might this have on gender differences in patients with aphasia?

4. What 3 conclusions did Bryan Woods and Hans-Leukas Teuber draw regarding the reorganization of language ability following brain injury? Would there be differences in such reorganization in people who are hearing impaired?

5. Through what anatomical system is the right hemisphere able to understand language? What happens to language ability following a removal of the right hemisphere? In what ways do individuals who have had their right hemisphere removed differ from split-brain patients?

6. What were the symptoms of the patient “Tan” which, when presented to neurologist Paul Broca in 1861, propelled Broca to his theory regarding hemispheric language lateralization? Based on current methods of assessment, would Broca's theory still be considered valid today? Why or why not?

7. Which type of study would be best used in order to assess anatomical asymmetry and why?

8. Which type of study is most useful in assessing the connection between hemispheric language lateralization and handedness, and why?

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Bear, M. F., Connors, B. W., Paradiso, M. A. (2007). Neuroscience: Exploring the Brain, 3rd edition. Lippincott Williams & Wilkins: USA.

Branch, C., Milner, B., Rasmussen, T. (1964). Intracarotid Sodium Amytal for the Lateralization of Cerebral Speech Dominance. Journal of Neurosurgery, Vol. 21, No. 5, pp 399-405.

Clower, W. T., Finger, S. (2001). Discovering Trepanation: The Contribution of Paul Broca. Neurosurgery, Vol. 49, No. 6, pp 1417-1426.

Geschwind, N., Levitsky, W. (1968). Human Brain: Left-Right Asymmetries in Temporal Speech Region. Science, New Series, Vol. 161, No. 3837, pp. 186-187.

Hickok, G., Bellugi, U., Klima, E. S. (1998). The neural organization of language: evidence from sign language aphasia. Trends in Cognitive Sciences, Vol. 2, No. 4, pp 129-136.

Jay, T. B. (2003). The Psychology of Language. Prentice Hall: New Jersey, USA.

Knecht, S., Deppe, M., Ebner, A., Henningsen, H., Huber, T., Jokeit, H, Ringelstein, E.-B. (1998). Noninvasive Determination of Language Lateralization by Functional Transcranial Doppler Sonography : A Comparison With the Wada Test. Stroke, Vol. 29, pp 82-86.

Knecht, S., Deppe, M., Drager, B., Bobe, L., Lohmann, H., Ringelstein, E.-B., Henningsen, H. (2000). Language lateralization in healthy right-handers. Brain, Vol. 123, pp 74-81.

Kolb, B., Whishaw, I. Q. (2009). Fundamentals of Human Neuropsychology, 6th edition. Worth Publishers: USA.

Ojemann, G. A. (1991). Cortical Organization of Language. The Journal of Neuroscience, Vol. 7, pp 2281-2287.

Penfield, W. (1963). The Brain's Record of Auditory and Visual Experience. Brain, Vol. 86, No. 4, pp. 595-696.

Purves, D., Augustine, G. J., Fitzpatrick, D., Hall, W. C., LaMantia, A., McNamara, J. O., White, L. E. (2008). Neuroscience, 4th edition. Sinauer Associates, Inc.: Massachusetts, USA.

Wada, J., Rasmussen, T. (1960). Intracarotid Injection of Sodium Amytal for the Lateralization of Cerebral Speech Dominance Experimental and Clinical Observations. Journal of Neurosurgery, Vol. 17, No. 2.


Testing for Mixed Dominance

Testing for mixed dominance is no too complicated. To test their dominant eye, give your child something to look through with one eye like a microscope, kaleidoscope, or a paper towel roll. The eye they use to look through the object is, in most cases, their dominant eye. To test their legs, roll a ball toward their midline and have them kick it back. As long as the ball really rolled toward the center line of their body, they will kick with their dominant leg.

To test their dominant ear, watch which ear they turn toward a noise they are struggling to hear or hand them a phone and see which ear they put the phone up to. With hands, a good place to start is by watching what hand they write with. However, it doesn’t hurt to test out dominance through throwing, catching or another motor activity because hand dominance can also change between activities in mixed dominance if the child was ever encouraged to use a different hand than what was normal for them. Our hope is that dominance shows up on all the limbs on the same side. If it doesn’t, don’t fret. There things you can do to help.


Can drawing a duck define a person's hemispheric dominance? - Psychology

Experiment Module: What Split Brains Tell Us About Language

Communication between the two hemispheres of the brain is made possible by the bundles of axons, or commissures, that connect them. The largest of these bundles, known as the corpus callosum, consists of about 200 million axons running from one hemisphere to the other.

In the 1950s, American neuroscientist Roger Sperry and his team discovered that curiously enough, severing the corpus callosum in the brain of a cat or monkey had no notable effects on the animal&rsquos behaviour. Only some special experimental protocols revealed that these animals were actually sometimes behaving as if they had two brains.

This absence of major deficits in animals with a severed corpus callosum gave neurosurgeons the idea of performing this operation on certain patients whose frequent, severe epileptic attacks were ruining their lives. In some of these patients, the epileptic focus was located in only one hemisphere, so this operation could successfully prevent the attacks from propagating to the other hemisphere. Having had this operation, these “split-brain” individuals could go back to enjoying their lives as with the animals in Sperry’s experiments, their day-to-day behaviour was practically unaffected by the separation of their brains into two halves.

The renowned American neuropsychologist Michael Gazzaniga, who began his career working with Roger Sperry, has developed several devices for analyzing functional differences between the two hemispheres in split-brain patients. The idea behind these devices is to deliver stimuli in such a way that they reach only one hemisphere, and then to observe how this hemisphere manages to process these stimuli on its own.

To study language, Gazzaniga asked his subjects to focus on a point at the centre of a screen. He then projected images, words, and phrases onto the screen, to the left or right of this point. By flashing these items quickly enough that the subjects&rsquo eyes had no time to move, Gazzaniga was able to “talk” to just one of the hemispheres at a time. Information projected in the subjects&rsquo left visual field was received by the right hemisphere, while information projected in the right visual field was received by the left.

The subjects could easily repeat numbers or words or describe images projected in their right visual field, because the left hemisphere, which received and processed this information, is the dominant hemisphere for language. Similarly, when asked to close their eyes and feel an object with their right hand, they could describe the object readily.

But when the visual stimuli were projected in the subjects&rsquo left visual field or when they were asked to feel objects with their left hand, their performance was quite different: they could not describe the stimuli or objects concerned. In fact, for the visual stimuli, they even said that they hadn&rsquot seen anything at all!

Though the right hemisphere does have some serious gaps in its language-processing abilities, it is not completely devoid of them. It can read and understand numbers, letters, and short statements, so long as the individual does not have to demonstrate this understanding verbally.

For example, if the name of an object is projected so that a subject with a severed corpus callosum sees it with the right hemisphere only, he will say that he doesn&rsquot see anything, because the severed connection has in fact prevented his left hemisphere, which is dominant for language, from doing so. But if the experimenter then asks the subject to use his left hand to choose a card with a drawing of the object whose name he saw, or to identify this object by feeling it with his left hand, he will have no problem in performing the task. Thus the right hemisphere cannot express itself in complex sentences, but it clearly can recognize words.

In another experiment, a photo of a naked man was presented to the right hemisphere of a female split-brain patient. When asked about the nature of the photo, she began to laugh and explained that she didn&rsquot know why she was laughing, but that maybe it was because of the machine that was projecting the images.

Certain experiments that Gazzaniga conducted with split-brain patients also led him to develop the concept of the “left-hemisphere interpreter”. In one of these classic experiments, the split-brain patient had to point with his two hands at pictures of two objects corresponding to two images that he had seen on the divided screen (one with each of his two separated hemispheres). In the test shown here, the patient&rsquos left hand is pointing at the card with a picture of a snow shovel, because the right hemisphere, which controls this hand, has seen the projected image of a winter scene. Meanwhile, his right hand is pointing at the card with a picture of a chicken, because his left hemisphere has seen the image of a chicken&rsquos foot.

But when the patient is asked to explain why his left hand is pointing at the shovel, his talking hemisphere—the left one—has no access to the information seen by the right, and so instead interprets his behaviour by responding that the reason is that you use a shovel to clean out the chicken house! Experiments like this show just how ready the brain is to provide language-based explanations for behaviour.

Gazzaniga&rsquos experiments thus helped to demonstrate the lateralization of language as well as other functional differences between the left and right hemispheres.


Debunking neuromyths

All neuromyths have their origins in real scientific knowledge. However, for one reason or another, people distort the information or only look at one very specific aspect of the research. Next, we’ll debunk the three most common neuromyths.

1. Humans only use 10% of their brains

This is probably the most widespread neuromyth of all, repeated by educators, parapsychologists, and advertising companies, among other people. The myth suggests that humans only use 10% of their brain, but that you can increase that percentage with certain training or learning techniques. It implies that the other 90% of your brain is basically unused.

The grain of truth in this neuromyth is that the brain is a powerful organ and, because of the way it works, it never operates at 100%. That doesn’t mean that you can’t improve your abilities. The improvements, however, happen by strengthening connections, creating new networks, and improving brain health. It isn’t a question of “space”.

If your brain was 100% activated, it would require an enormous amount of energy. It would also trigger every kind of behavior all at the same time. The brain works by activating different zones that connect to each other in order to trigger certain behaviors or cognitive processes.

Scientists have also seen that when you sleep, your brain still shows some level of activity. So, you do use 100% of your brain, but not all at the same time.

2. You can learn better if you follow your “learning style”

Another widespread belief is that students learn better when the presentation of the information coincides with their learning style. People usually identify three different styles: auditory, kinesthetic, and visual. According to this belief, you should teach each student differently, catering to their learning style. Some schools have even gone so far as to label children with the first letter or their learning style.

Given the pervasiveness of this belief, you might be surprised that there’s no scientific evidence to support it. Nor have any studies shown that people learn better when they receive information through a specific channel. On the contrary, the research that has been done on the subject is notably deficient.

Nevertheless, it’s certainly true that each individual brain is the result of distinct experiences and biology. Thus, it makes sense that each individual has a preference when it comes to the learning process. But is that better?

What we do know for sure is that when your brain receives several stimuli that aren’t integrated in a sensorial way, it can cause confusion. In that case, your brain has to draw on more resources to absorb and process the information. When the information is rich and covers several sensory channels, on the other hand, the learning experience is stronger.

3. The hemispheres of the brain are independent and determine your personality

This popular myth argues that each brain hemisphere is responsible for certain processes and that they work independently. Another part of this myth is that one side of the brain is always dominant and that that determines certain personality traits.

According to this idea, the right hemisphere is responsible for more comprehensive thinking. It’s more artistic, sensorial, and carefree. The left brain, on the other hand, is analytic, responsible, accurate, structured, and logical.

Scientific research has shown that these ideas about the right and left brain are patently untrue. It turns out that both hemispheres receive and process all kinds of information. However, there are certain functions that tend to happen more in areas of the brain that are on one side of the brain or the other. Nevertheless, these areas process information in an interconnected way, unless there’s some kind of brain disorder at play.

In addition, although being right or left-handed implies the domination of one hemisphere, this has nothing to do with people’s personalities or the way they process information. Right or left-handed, each person’s skills and abilities are determined by experience and other hereditary factors.


INTEGRATING THE TWO HEMISPHERES OF THE BRAIN

The ancient Egyptians were the first to notice that the left brain tends to control the right side of the body, while the right brain tends to control left side of the body. Although the two hemispheres are almost identical in terms of structure and function both hemispheres to a completely different way and are associated with various functions and activities. This is known as specialization and lateralization. Lateralization is evident if we consider the phenomenon of people prefer to use the right hand or left or preference to the left or right ear. However, the preference of the individual to use the left or right hand writing is not a sufficient indicator for the localization of brain function.

Imagine looking down through the top of your head to the cortex of your brain. You will notice that it is made of two halves called hemispheres: one left side, other than the right. Left and right side of the brain is associated with a complex network of nerve fibers called the corpus callosum. This neurological bridge is responsible for the transfer of information between the left and right hemisphere, allowing the brain to function as a whole.

Many studies have shown that most individuals tend to dominate the left brain side, mostly because traditional methods of learning, which leads to incomplete development of the right. One of the factors that affect the processing of information is whether the individual has a tendency to dominance left or right brain hemisphere. Traditional teaching methods are based on repetitive memorization and learning, learning theories and rules and their reproduction without solutions and practical application. The traditional style of learning supports dominance left brain hemisphere and for individuals of which use the same processing information or possessing logical and analytical skills. By contrast a number of individuals who tend to dominate the right brain hemisphere will experience barriers in the traditional educational system, because they process the information holistic, intuitive, or through the right hemisphere.

There are a range of options and opportunities that can promote progressive learning style or more holistic approach will focus to the individual needs and self expressing and which will encourages mental agility, critical and creative thinking, coming up with new solutions and their practical application. Among them: an interactive group work, presentation of visual information, a storm of ideas, association with images, use of computers, use of imagination and research techniques, humor, role playing, simulations, and learning music and drawing which positively acts of emotional state.

To cite one example, children receive the task, report book. If you have a choice between: to write a report to present the report to draw a scene from the book, to design a poster to play a scene from the book, or to create a different end of the book, you will notice a fascinating phenomenon that every child gravitates to its neurological advantages. Those who tend to right hemisphere dominant choose to draw, play or create, while they tend to the left dominant hemisphere choose to speak or write.

The concept of diversity implies that each individual is unique, and that everyone has a different learning style. It says that the individual who tends to left or right brain dominance is useful to develop the other hemisphere. Of great importance is the possibility that the two hemispheres would operate in tandem, rather than independently, the possibility of integrating them. Integration leads to the ability to tune in unpredictable situations and new challenges.

Also, much of the research for the development of both sides of the brain in children showed that less used connections between left and right.

Research psychologists US Army Institute of behavioral and social sciences, Fort Benning and the Institute in Melbourne, Australia, have shown, however, that the ability of subjects like mathematics is strongest when both hemispheres working together.

Children brain twice more active than adult

Techniques using the right hemisphere are based on turning work into play, using the art presented. Information is representing as organized in space, using colors, signs, symbols. It is this approach made revolution in the learning process.

Running any kind of cross-lateral exercises and balance exercises tend to increase connections in the brain. Increasing hemispheric integration can improve creativity and general emotional and physical awareness.

The use of the abacus (ancient calculating machine) with VAK methodology (visual, auditory and cinematographic receiving and storage of information) and mathematics allows the use of both sides of the brain and their coordination, which made the development and progress of the entire brain capacity and proper mental formation. When children practice the visual abacus, they actually develop their imagination and which is a function of the right hemisphere of the brain. Combining this with some words spoken in rhythm and rhyme begins to activate functions and left hemisphere. Regular exercise of 15 minutes this way actually provides a very useful and effective exercise (training) of the brain and causes and implement many new qualities in the child. One of the most important are: visualization and concentration which is supported by listening skills and photographic memory, speed, accuracy.

According to experts in the field of brain development in children in the first years of life, the neurons in our brain form new connections with admirable rate of 700-1000 connections per second – at a pace that is not repeated in life. In the early development of the child’s brain is twice as active as compared to the brains of adult animals and experiences of this period is determined by the capacity of the brain. The brain, integration means that certain areas with their unique features, become connected to each other through synaptic connections. These integrated connections allow more complex functions to occur such as awareness, empathy, intuition and moral.

If children are encouraged to learn to be ambidexter, or to use both hands equally, it will promote synchronization and hemispheric integration and full growth of the brain. Studies have shown that individuals who are ambidexter, on average more determined in solving difficult tasks and are more emotionally resilient and adaptive.

According to the words of Dr. Dan Siegel (Dr. Dan Siegel), author of many books on child development, we need to help children build reflective intra and inter personal relations. The brain is a social organ of the body. When he experienced reflective relations creates elasticity. Elasticity is the ability to meet challenges, to examine the positive and encourage creative ideas that will take us forward together.

Logical and creative hemisphere

The theory of right brain / left brain comes from the work of Roger C. Sperry (Roger W. Sperry) who was awarded the Nobel Prize in 1981. According to this theory left hemisphere is responsible for analytical thinking, facts, logic, science, words and verbal expression, critical thinking, numerical skills, writing, while the right hemisphere is responsible for awareness of art, musical awareness, creativity, visualization, memory, intuition , feelings and holistic thinking.

Frequent broad generalizations popular psychology contributed to the distinctive labels as “logical” for left hemisphere and “creative” to the right hemisphere. These labels are not supported by studies of lateralization. Recent research suggests that the brain is not a dichotomy as it was considered, but that the two hemispheres are mutually related. Both hemispheres cooperate with alternating shift of responsibility, depending on the task. This is called dominance hemispheres. In the broadest sense hemispheric dominance is changed every 90 minutes. You can easily observe this phenomenon if you notice which nostril is open.

@ Author Copyright – Children’s Academy “Brainobrain Europe”


Left brain vs. right brain: Fact and fiction

The two hemispheres or sides of the brain — the left and the right — have slightly different jobs. But can one side be dominant and does this affect personality?

Some people believe that a person is either left-brained or right-brained and that this determines the way they think and behave.

In this article, we explore the truth and fallacy behind this claim. Read on to learn more about the functions and characteristics of the left and right brain.

Share on Pinterest A person’s brain activity can vary, depending on what they are doing.

The brain is a complex and hardworking organ. It is made up of as many as 100 billion neurons or brain cells but only weighs 3 pounds.

It is an energy-intensive organ, making up around 2 percent of a person’s weight but using a huge 20 percent of the body’s energy.

The left and right sides of the brain are connected by a great number of nerve fibers. In a healthy brain, the two sides communicate with one another.

The two sides do not necessarily have to communicate, though. If a person has an injury that separates the two brain hemispheres, they are still able to function relatively normally.

According to the left brain vs. right brain belief, everyone has one side of their brain that is dominant and determines their personality, thoughts, and behavior.

Because people can be left-handed or right-handed, the idea that people can be left-brained and right-brained is tempting.

Left-brained people are said to be more:

  • analytical
  • logical
  • detail- and fact-oriented
  • numerical
  • likely to think in words

Right-brained people are said to be more:

  • creative
  • free-thinking
  • able to see the big picture
  • intuitive
  • likely to visualize more than think in words

Recent research suggests that the left brain vs. right brain theory is not correct.

A 2013 study looked at 3-D pictures of over 1,000 people’s brains. They measured the activity of the left and right hemispheres, using an MRI scanner.

Their results show that a person uses both hemispheres of their brain and that there does not seem to be a dominant side.

However, a person’s brain activity does differ, depending on what task they are doing.

For example, a study in PLoS Biology says that the language centers in the brain are in the left hemisphere, while the right hemisphere is specialized for emotion and nonverbal communication.

Contributions towards this ‘brain lateralization’ research won Roger W. Sperry the Nobel Prize in 1960. However, popular cultural exaggeration of these findings led to the development of beliefs of left brain and right brain personalities.

Although people do not fall neatly into the categories of left-brained or right-brained, there are some differences in what the left and right hemispheres do.

Differences in the left and right brain hemisphere function exist in:

This is the domain of the right brain, in both humans and also in non-human primates. Emotions are expressed and recognized in others by the right brain.

The left brain is more active in speech production than the right. In most people, the two main language areas, known as Broca’s area and Wernicke’s area, are found in the left hemisphere.

Sign language

Visually based languages are also the domain of the left brain. People who are deaf show speech-like brain activity when watching sign language.

Left- and right-handed people use the left and right brain differently. For example, a left-handed person uses their right brain for manual tasks and vice versa.

Handedness is inbuilt, and it can even be detected while the baby is in the womb. Some babies prefer to suck their left or right thumb from as early as 15 weeks.

The two brain hemispheres also differ in what they pay attention to.

The left side of the brain is more involved with attention to the internal world. The right side is more interested in attending to the external world.

Recent brain imaging studies have shown no differences between males and females in terms of their brain lateralization.

The side of the brain used in each activity is not the same for every person. The side of the brain that gets used for certain activities may be influenced by whether a person is left- or right-handed.

A 2014 study notes that up to 99 percent of right-handed individuals have the language centers in the left of the brain. But so do about 70 percent of left-handed individuals.

Hemispheric dominance varies from person to person and with different activities. More research is needed for science to fully understand all of the factors that affect this.

The theory that a person is either left-brained or right-brained is not supported by scientific research.

Some people may find the theory does align with their aptitudes. However, they should not rely on it as a scientifically accurate way to understand the brain.

The left brain vs. right brain personality belief may have lasted for so long because, in reality, brain activity is not symmetrical, and it does vary from person to person.


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