How does being left handed affect the brain

Are Left-Handed People Smarter?

The notion that lefties are smarter than righties has been floating around for some time.

While some studies have suggested there may be a link between left-handedness and a higher IQ, others have shown that right-handed people may actually have the edge.

Here’s what the research says when it comes to lefties and IQ.

Left-handed people, also known as “lefties” and “southpaws,” make up about 10 percent of the population.

Famous left-handed people

Some famous lefties include great minds, such as:

philosopher Aristotle
French emperor Napoleon Bonaparte
baseball legend Babe Ruth
Renaissance artist Leonardo DaVinci
former president Barack Obama

Microsoft founder Bill Gates

Historically, left-handed people have been viewed and treated as outcasts. In the Middle Ages, left-handed people feared being accused of witchcraft.

As recently as the early 20th century, many educators in the United States forced left-handers to “retrain” their natural tendencies in order to become right-handed.

Scientists also used to think that left-handedness was due to minor brain damage in early development.

These myths have been debunked over the years, and some have asserted that being left-handed is actually associated with higher intelligence.

While the claim is intriguing, medical literature reveals inconclusive results.

The belief that handedness is associated with intelligence has been around for centuries.

Research seems to support both sides of the argument. Here’s what studies have shown in favor and against the idea that left-handedness has anything to do with intelligence.

Are right-handed people smarter?

A 2010 study in the Journal of the International Neuropsychological Society revealed that strong right-handers seemed to perform slightly better on cognitive tests when compared to left-handers.

A 2015 study in Neuroscience & Biobehavioral Reviews looked at five meta-analyses that included data on more than 16,000 individuals. They found no difference in IQ levels among left- and right-handed people, but left-handers appeared to be more likely to have an intellectual disability.

However, this study indicated that people who were intellectually gifted or following typical development were also just as likely to be left-handed.

A study in Neuroscience and Biobehavioral Reviews looked at 18 studies measuring the full IQ scores of more than 20,000 participants.

Although data suggested that right-handed people had slightly higher IQ scores compared to left-handers, the scientists noted that intelligence differences between right and left-handed people were negligible overall.

Are left-handed people smarter?

Other studies have found lefties seem to have the upper hand when it comes to smarts.

A 2007 study in the Journal of the Indian Academy of Applied Psychology found that, out of 150 subjects, left-handed participants were significantly more likely to perform better on an intelligence test than right-handed people. Right-handers also took more time to complete the test.

Another study in the journal Brain in 2019 revealed that there are genetic differences between left-handers and right-handers.

Examining data on about 400,000 people, scientists discovered that the left and right hemispheres of the brain were better connected and more coordinated in regions involving language in left-handed people.

These traits suggest that left-handed individuals may have superior verbal skills.

Handedness, or hand preference, is the tendency to be more comfortable and skilled when using one hand over the other to perform tasks.

While right-handedness and left-handedness are well-known, there are also some less common variations, including:

Mixed-handedness: favor different hands depending on the task
Ambidextrousness: can perform tasks equally with either hand

Influences on handedness

Scientists believe your hand preference is a complex characteristic that’s influenced by many factors, including:

genetics
environment
random chance

Hand preference develops before birth and becomes more obvious during early childhood and throughout one’s life.

Researchers believe hand preference may have to do with the developmental differences between the right and left hemispheres of the brain. The right hemisphere controls movement on the left side of the body, while the left hemisphere controls movement on the right side of the body.

Recent studies have also suggested that multiple genes, maybe even close to 40, are related to hand preference.

Children of left-handed parents are more likely to be left-handed than children of right-handed parents. But because lefties are comparatively rare, most children of left-handed parents are right-handed.

Cultural influences, environment, and prenatal exposures may also play a role in determining handedness.

Intelligence can be defined in many different ways.

In psychology, for instance, intelligence may be described as possessing one or a combination of the following attributes:

a higher ability level, such as abstract reasoning, problem-solving, or decision-making
ability to learn
emotional knowledge
creativity
adaptation

There are different theories of intelligence and ways to measure it, including the well-known intelligence quotient (IQ) tests.

While certain exams can provide useful information, they aren’t the only way to assess intelligence or validate this complex label.

Some research has shown lefties may be more likely to develop certain conditions, including:

Parkinson’s disease
schizophrenia
breast cancer
post-traumatic stress disorder (PTSD)
learning disabilities, such as dyslexia

But other studies reveal lefties might have the advantage in certain areas.

Research shows left-handed people may have a lower risk of developing ulcers and arthritis. They may also recover more quickly from strokes.

An older article in the American Journal of Psychology suggests that left-handed people may be better at divergent thinking, a thought process used to generate creative ideas.

The southpaw advantage

Studies have also suggested that lefties excel athletically, sometimes dubbed the “southpaw advantage.”

While only about 10 percent of the general population consists of left-handed people, they are overrepresented in some elite sports.

Hand preference is highly subjective and personal. Most people determine their handedness during childhood, sometimes with the help of a parent or caregiver.

But if you’re not sure if you’re a leftie or a righty, ask yourself this question: Which hand do you perform most activities with, not just writing?

If you happen to use one hand for about half of the activities and the other for the other half, you may be mixed-handed.

While there are curious differences between lefties and righties, a higher intelligence level probably isn’t one of them.

Many studies show mixed results when examining this complicated link, leading researchers to conclude that left-handed people are no smarter than their right-handed counterparts.

Your Left-Handed Brain · Frontiers for Young Minds

Abstract

While most people prefer to use their right hand to brush their teeth, throw a ball, or hold a tennis racket, left-handers prefer to use their left hand. This is the case for around 10% of all people. There was a time (not so long ago) when left-handers were stigmatized (see Glossary) in Western (and other) communities: it was considered a bad sign if you were left-handed, and left-handed children were often forced to write with their right hand. This is nonsensical: there is nothing wrong with being left-handed, and trying to write with the non-preferred hand is frustrating for almost everybody. As a matter of fact, science can learn from left-handers, and in this paper, we discuss how this may be the case. We review why some people are left-handed and others are not, how left-handers’ brains differ from right-handers’, and why scientists study left-handedness in the first place.

Why are You Left-Handed?

Despite many years of research, the reason why one person turns out to be a left-hander and another does not remains a mystery. Handedness is partly heritable (see Glossary): left-handed parents tend to have more left-handed children than right-handed parents do. Studies that compared identical twins to fraternal twins (see Glossary) show that the heritability is around 25% [1], which suggests a genetic contribution to hand preference. Note, however, that if handedness is only 25% heritable, then the majority of the factors contributing to left-handedness is not straightforwardly genetic. A much debated influence is the level of the hormone testosterone in utero (in the womb) while an unborn child (fetus) is developing. Another possibility is that handedness is influenced by random (“chance”) processes that occur during the early development of an unborn child, when it is still very small. Regarding the heritable factors, researchers have found several genes which may be involved in handedness. Interestingly, it seems that there is not one gene which contributes to determining whether people are left-handed or not. Most likely, different genetic influences are involved.

Of course, children learn from their caregivers, so one may expect that if one of the parents is left-handed, the child might become left-handed just by imitation. One reason why this cannot be the full story is that hand preference can already be observed before birth. Fetuses like to move around, and one can predict a child’s hand preference reasonably well by looking at which arm and hand they prefer to move before birth, as can be seen with ultrasound scanning [2]. This observation of fetal handedness is at odds with the finding that some children seem to switch their hand preference, at least up to the age of 2 [3, 4]. Perhaps some people are left- or right-handed at birth, whereas others develop their preference later on, during the first years of life.

Are you confused about what makes a person left-handed or not? So are we! Whatever the exact causes may be, this is not a simple story, but a very complex interplay of genes, environment, and chance. Let us leave this topic for now, and have a look at the left-handed brain.

Is the Left-Handed Brain Different?

Sometimes, people are amazed to hear that the brains of left-handers are different from those of right-handers. But it is clear that they should differ in some respects: left-handers use their hands (and feet) differently than right-handers do, and they do this often over the course of a lifetime. It is only natural that the parts of the brain that control movements should be different in left-handers and right-handers (Figure 1). Compare this to skilled musicians: they practice fine movements a lot, and this influences their brains¹. To study exactly how the brains of left- and right-handers differ, we need to look at brain lateralization.

Figure 1 - Brain activation when participants imagined performing common hand actions.
Left- and right-handed participants imagined performing actions such as throwing or writing. It is striking that in left-handers (yellow), only areas of the right side of the brain were activated, whereas it was the opposite in right-handers (blue). Left-handers thus imagine themselves writing with their left hand, which is mainly controlled by the right hemisphere, and vice versa for right-handers. Picture from Willems et al [8].

Brain lateralization refers to the fact that the left and right sides of the brain are not the same. The two sides differ in their anatomy, and also in what they do. By the way, lateralization is also found in the rest of the body: the two arms look slightly different, and are capable of doing different things; the heart is lateralized to one side of the body cavity, etc. Left-handers are distinct from right-handers in that they tend to have less lateralization in the brain. A well-known example of this is language, which is mainly a function of the left side of the brain in right-handers². Although left-sided language areas in the brain are still important in left-handers, the difference between left and right sides tends to be less strong. A similar example comes from face perception, which is rightward-lateralized in the majority of people, meaning that mainly right-sided parts of the brain are responsive to faces. Again, left-handers tend to use both left and right regions of the brain relatively often when they see a face [5].

Do Left-Handers Think Differently?

Does this mean that left-handers think differently? Well, yes and no. There have been lots of suggestions of left-handers’ increased creativity, but there is very little firm evidence on this. Increased musical abilities are another often-cited skill that left-handers might possess, but again, there is very little evidence to support this. Many claims about left-handers’ superior skills are based on lists of famous musicians that circulate on the internet. While amusing, these lists span several decades of pop music, and you will find (if you try) that for every left-handed guitarist in such lists, you could easily come up with enough right-handed guitarists to match the usual 9:1 ratio of right- and left-handers in the population. Although there is no good evidence for left-handers being more gifted than right-handers, the opposite is also true: there is no clear evidence that left-handers perform more poorly on tests of cognition. This had been suggested for a long time (see our comment above on stigma).

Left-handers may think differently in another respect, though. A potent idea is that we understand action words like “writing” by using the parts of our brains that control our own movements, as though we were writing ourselves when we see or hear the word “writing.” This idea is sometimes called “embodied cognition.” It was tested by looking at activity of the left and right motor cortex (a brain region involved in movement) in left- and right-handed people while they listened to words such as “writing” [6]. Left-handers activated the motor cortex that controls their left hand, whereas right-handers activated the motor cortex that controls their right hand – as if they were really writing, while they were only listening to the word.

On a related note, left- and right-handers differ in how they judge positive and negative attributes of things in the space around them. In one experiment, participants had to judge “Fribbles” (nonsense figures; see Figure 2) in terms of honesty and intelligence. The figures were presented on either the left or right side of a screen. Left-handers rated figures presented on the left in more positive terms, and right-handers rated figures on the right in more positive terms [7].

Figure 2 - Participants were asked to circle which of two “Fribbles” they thought was most intelligent, happy, etc.
Left-handers rated Fribbles presented on the left side of the page as more positive, whereas right-handers did the opposite. The explanation for this finding was that left-handers act most fluently with the left side of their body, and right-handers with the right side of their body. Because of this fluency difference, positive and negative attitudes are also mapped onto opposing sides of space [7, 9].

It seems that the way in which we do things with our hands influences our thinking, at least to some extent.

Why Do We Study Left-Handedness?

Left-handedness is an intriguing phenomenon in its own right. However, scientists do not study left-handedness just because it is a fun topic. Left-handedness can shed light on diverse issues that go beyond the study of hand preference per se. Here are two more examples, in addition to the research we already described:

Human uniqueness. Other primates (e.g., the great apes) do not show such a strong population bias toward using the right hand as humans do. Over the course of evolution, there must have been changes in the brain that resulted in most humans preferring to use their right hands, while at the same time maintaining a stable minority that prefers to do things with the left hand. Why was this case, and what could have been the advantages? The lateralization of language in the brain (see above) has led to speculation that early humans started to communicate with their hands first, and only developed spoken language later.
Genes that create left-right asymmetries in the brain. Identifying genes that influence hand preference may shed light on the basis of lateralization of the brain and other body functions. How this arises during development is still poorly understood, but it is a very important aspect of our biology.

Summary

Left-handers are a sizeable minority of people (at least 10%). Hand preference is partly heritable, pointing to a genetic contribution. However, the relevant genes are likely to interact with environmental and chance factors to determine the handedness of a specific person. The brains of left-handers and right-handers are somewhat different. Left-handers tend to have less lateralized brains, meaning that the two halves of the brain are less distinct than in right-handers. The study of left-handers can help us answer several important scientific questions. All of this means that left-handers have many reasons to feel special, for after all, the large majority of people are not left-handed. At the same time, bold claims about creativity and other ways in which left-handers may be super-gifted are probably not true.

Footnotes

[1] ↑ Also, individuals who are born with exceptional properties for the parts of their brains involved in movement and music perception may be predisposed to become skilled musicians.

[2] ↑ This does not mean that the right side of the brain does nothing during language comprehension. Quite the contrary, it is also active, but less so than the left side.

Glossary

Stigmatization: ↑ To disapprove of people with a certain characteristic or behavior.

Identical twins and Fraternal twins: ↑ Identical twins develop from the same fertilization and therefore share virtually all of their DNA. They differ from fraternal twins, who develop from different fertilizations and are only genetically related, like any other pair of siblings.

Heritable: ↑ A characteristic that can be inherited, because genes affect the way it develops.

Acknowledgements

We are thankful to Hélène Cochet and Jacqueline Fagard for their helpful suggestions on the developmental section.

References

[1] ↑ Medland, S. E., Duffy, D. L., Wright, M. J., Geffen, G. M., Hay, D. A., Levy, F., et al. 2009. Genetic influences on handedness: data from 25,732 Australian and Dutch twin families. Neuropsychologia 47:330–7. doi: 10.1016/j.neuropsychologia.2008.09.005

[2] ↑ Hepper, P. G. 2013. The developmental origins of laterality: fetal handedness. Dev. Psychobiol. 55:588–95. doi: 10.1002/dev.21119

[3] ↑ Cochet, H. 2012. Development of hand preference for object-directed actions and pointing gestures: a longitudinal study between 15 and 25 months of age. Dev. Psychobiol. 54:105–11. doi: 10.1002/dev.20576

[4] ↑ Fagard, J., and Lockman, J. J. (2005). The effect of task constraints on infants’ (bi)manual strategy for grasping and exploring objects. Infant Behav. Dev. 28:305–15. doi: 10.1016/j.infbeh.2005.05.005

[5] ↑ Willems, R. M., Peelen, M. V., and Hagoort, P. (2010). Cerebral lateralization of face-selective and body-selective visual areas depends on handedness. Cereb. Cortex 20:1719–25. doi: 10.1093/cercor/bhp234

[6] ↑ Willems, R. M., Hagoort, P., and Casasanto, D. 2010. Body-specific representations of action verbs: neural evidence from right- and left-handers. Psychol. Sci. 21:67–74. doi: 10.1177/0956797609354072

[7] ↑ Casasanto, D. 2009. Embodiment of abstract concepts: good and bad in right- and left-handers. J. Exp. Psychol. Gen. 138:351–67. doi: 10.1037/a0015854

[8] ↑ Willems, R. M., Toni, I., Hagoort, P., and Casasanto, D. 2009. Body-specific motor imagery of hand actions: neural evidence from right- and left-handers. Front. Hum. Neurosci. 3:39. doi: 10.3389/neuro.09.039.2009

[9] ↑ Blackman, C. 2009. Lefty or Righty? A new hold on how we think. Stanford Report. Available at: http://news.stanford.edu/news/2009/august3/lefty-decision-study-080509.html

What is the difference between the brain and behavior of right-handers and left-handers

Why left-handers and right-handers cannot be treated equally, how the leading hand decides for us who to vote for in elections, how to change the idea of good and bad with a glove in 12 minutes, is it good to be ambidextrous - these and other questions are answered by the science department of Gazeta.Ru.

Pens, scissors, cars, computer mice... All these things are designed for 85% of humanity - right-handers. In recent years, scientists have begun to pay attention to left-handers as completely different, differently thinking and living individuals. Whether you are left-handed or right-handed affects not only which hand you write with, but also how you look at the world and how you interact with it, scientists have found.

The hand votes for the mind

Researchers from the University of Chicago state that when performing habitual actions, people subconsciously choose the side that is more convenient and comfortable for them - and this is the side of the working hand. This means that if a right-handed person sees two equally attractive people in a bar, he will instinctively get to know the person on the right side. Similarly, a person will behave in a store: not seeing much difference between the two products, left-handers choose the left product, and right-handers choose the right one.

They become left-handed in the womb

The gene responsible for the formation of body symmetry in the early stages of the development of the body, along the way, controls . ..

September 13 13:59

Why do right-handers and left-handers think so differently? Study lead author Daniel Casasanto suggested that people's concept of choosing "good" and "bad" depends in part on which hand they use more often. He says that people can act much more freely with the dominant hand, so they unconsciously associate good things with it.

If this fact seems quite logical, then the following observation of scientists was quite unexpected for them. It turned out that this behavior is also transferred to the choice of candidates on ballots during voting:

the probability that right-handers will choose a candidate whose name is written on the right side of the page is 15% higher than in the case of left-handers.

This means that if a person has not fully decided on his political preferences and expects to think while already in the polling booth, chance may well play a cruel joke on him.

Treat left-handed people differently

The authors of the study did not stop at simply fixing the characteristics of people's behavior - they found out that the differences between right-handers and left-handers extend to the brain. In right-handed people, the centers responsible for creativity and a sense of happiness are located in the left hemisphere, in left-handed people, the opposite is true. This means that brain specific therapies can have the opposite effect on a person depending on their dominant hand.

The brain is its own moralist

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01 December 09:35

“Scientists have long believed that the centers responsible for happiness and anger are located in the left hemisphere,” says one of the authors of the study, Dr. Daniel Casasanto. -

It turns out that this is true only for right-handed people, and the organization of brain activity depends on which hand is leading.

Such discoveries are of great importance for the treatment of various mental disorders - for example, depression, which doctors try to relieve the patient by increasing the activity of the left hemisphere. In fact, for left-handers, such treatment can have the opposite effect, so therapy should be directed to the right hemisphere.

How to throw down the glove of the mind

As mentioned above, right-handers subconsciously associate good with the right side of space, and bad - with the left, left-handers - vice versa. To test whether this behavior can be changed, scientists from the Max Planck Institute for Psycholinguistics and the University of Pennsylvania conducted a series of unusual experiments. More information about this study can be found on the pages of the journal Psychological Science.

Scientists proved that even

A few minutes of left-handed work can change the right-hander's perception that right is good and left is bad.

In the first experiment, people were asked to choose one of two products, one of two job candidates, and to rate which of the two alien creatures depicted in the pictures is smarter than the other. Right-handed people, as expected, were much more likely to choose right-handed objects, while left-handed people were much more likely to choose left-handed objects. The scientists then tested how right-handed people thought about good and bad after they lost the ability to use their right hand: either due to some kind of injury, or with artificial restrictions on the actions of the dominant hand (the subjects put a ski glove on their hand).

"Owl" is in the genes

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It turned out that those who lost the ability to fully use the right hand, considered the left "good" - just like "natural" left-handers. The same regularity was found in healthy students who performed various motor skills tasks requiring speed and dexterity with their right hand in a bulky glove.

After 12 minutes of such "clumsy" motor activity with the dominant hand, the right-handers changed their judgments about what is right - good, and left - bad.

Scientists say that people are used to thinking that their judgments are rational and their concepts are stable. But if wearing a glove for a few minutes can completely change people's usual judgments of what is bad and what is good, then perhaps our minds are more malleable than we previously thought?

Is it good to be ambidextrous?

There is an opinion among the people that the ideal and universal embodiment of human skills in relation to right-handedness and left-handedness is ambidexterity - the same possession of the right and left hands. Scientists have destroyed this myth: it turns out that the owners of this amazing ability have a much harder time in life than ordinary right-handers and left-handers.

Scientists say that children with ambidexterity are much more likely to experience problems with languages, health, perform worse at school and are prone to attention deficit hyperactivity disorder (ADHD).

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Researchers at Imperial College London and other European institutions suggest their findings could help teachers and health workers identify children who are most at risk of developing certain problems. This study was published in the journal Pediatrics .

Every hundredth child is an ambidexter. The researchers looked at nearly 8,000 children, 87 of whom were ambidexters, and found that between the ages of 7 and 8 years old, children with two hands were twice as likely to experience difficulties with mastering their native language and problems with school performance than their right-handed peers. .

When these children reached 15–16 years of age, ambidexters were again twice as likely to develop symptoms of attention deficit hyperactivity disorder. "Two-armed" teenagers, as in earlier ages, had more problems with language than right-handers.

At the moment, little is known about what contributes to ambidexterity in children, but researchers suggest that this may be due to the work of the hemispheres, as in right-handed and left-handed people. For a more detailed understanding of the problem, the researchers propose to deepen and continue further work. The scientists also emphasize that they only found in ambidexters an increased tendency to certain disorders and problems - this does not mean that such problems occur in all ambidexters without exception.

THE BRAIN OF RIGHT AND LEFT HANDERS - WHAT IS THE DIFFERENCE?

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About 10% of the world's population is not like the rest: they are lefties. Moreover, their difference is not just a mirror one. If for right-handed people the leading right hand is most often combined with the leading right eye and the leading right ear, then for left-handers these combinations are much more diverse. Even their brains are arranged somewhat differently than those of the right-handed majority, and this, as it turned out, applies not only to the dominance of the right (and not the left) hemisphere, but also to the principles of functional organization in general.

In the Laboratory of General and Clinical Electrophysiology of the Human Brain of the Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences, under the guidance of Doctor of Biological Sciences L. A. Zhavoronkova, the character of interhemispheric asymmetry of the brain of right-handers and left-handers was studied. For this, encephalograms were taken from the subjects in different states, which recorded the bioelectrical activity of different areas of the cerebral cortex.

It turned out, for example, that in a state of calm wakefulness, the cerebral hemispheres of right-handers work more synchronously than those of left-handers, and when moving the dominant hand, the brain of right-handers is activated locally in the left (leading) hemisphere, while in left-handers it is activated in both. The encephalogram of right-handers and left-handers also changed in different ways during falling asleep.

During another experiment, the subjects first sat with their eyes closed, and when they opened them, a light signal lit up in front of them, on which they had to fix their eyes. In right-handers, the effect of this signal disrupted the synchronism in the work of the hemispheres, while in left-handers, the picture changed insignificantly.

It seems that left-handers do not have such a clear distribution of roles between the sections of the cortex of the cerebral hemispheres, and this is precisely what affects his work during the transition from one functional state to another (for example, from wakefulness to sleep). Scientists believe that the cortex and subcortical structures in right-handers mutually suppress each other to a large extent, while in left-handers, on the contrary, they are mutually activated. Both minuses and pluses of "left-handedness" follow from this. So, for example, the cortex of left-handers is less able to suppress epileptic activity, and this apparently explains the fact that among them there is a much larger percentage of epileptics than among the human population in general.

On the other hand, the functional organization of the brain of left-handed people can contribute to the development of creative abilities, and it is not surprising that there are many brilliant musicians, architects, and artists among them.

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