Lefties and righties: interesting facts and differences. Why are most people right-handed?

We live in a society dominated by right-handed people. According to statistics, approximately 85-90% of the population actively use their right hand. The handles on the doors, the speed switch in the car, the doors in the wardrobes - everything is done for the convenience of right-handed people. The minority has to adapt, a few use special devices, the majority get along just fine without them.

Why are most people right-handed? To date, there is no definite answer to this question. There are several versions explaining this phenomenon.

One version is called the asymmetry of our body. The left arm is longer than the right, the foot of the right leg is larger in size than the left. Or vice versa. This asymmetry is observed throughout the human body, and the same situation occurs inside his body. It has long been an undeniable fact that the leading hand is determined by the brain. The left hemisphere controls the right side of our body, the left side is controlled by the right hemisphere. A left-handed person has a more developed right hemisphere, a right-handed person has a more developed left hemisphere. Scientists suggest that in most cases the left hemisphere of the brain is dominant over the right. Since the left side of the brain is dominant, it means that the right side of our body is more perfect and developed. This fact may explain why most of us are right-handed. If a person has a more developed right hemisphere, then it is more convenient for him to work with the left side of the body. He is left-handed.

The next version is intrauterine development. An experiment was conducted in which the progress of women's pregnancies was monitored. Using ultrasound, unborn babies were photographed and the image was examined. If the baby was sucking or actively moving right hand, they assumed that he was right-handed. In contrast, a left-handed person used his left hand. After birth, the children confirmed the scientists’ guesses. It was concluded that at 3-4 months of intrauterine development, future left-handers experience some changes in the brain. As a result, the right hemisphere begins to dominate the left. Over time, the changes are consolidated, and the right hemisphere is now responsible for speech and writing. The left hand becomes the leading hand. If such a “restructuring” has not occurred completely, then a person can equally control both the left and right sides of the body. They are called ambidextrous; they make up only 1% of the general population.

Another possibility is genetic inheritance. Children with a dominant right hemisphere of the brain are born in families in which the mother's side was left-handed.

The left hemisphere of the brain is responsible for abstract and logical thinking, right - for spatial and figurative. The hemispheres have different energy levels; the right one has an intense metabolism and is more excitable. In the left, the energy is reduced, excitations occur less frequently and weaker. Therefore, left-handers and right-handers are completely different people in their essence. Right-handed people have higher intelligence and find it easier to find mutual language in a team, they are sociable. Left-handed people do worse at school, but they are able to distinguish the finest shades of color and hear the slightest fluctuations in sounds and intonations. These are creative people.

IN old times Children at school had their left arm tied to their body in an attempt to retrain the child to be right-handed. As a result, children lost skills in using their left hand, and the acquired experience in working with their right hand was difficult and not fully developed. Today, reputable psychologists oppose such radical measures. If it is easier for a child to control his left hand, then he should not be prevented from doing so. And despite the fact that left-handers and right-handers think and perceive the world differently, they exist perfectly with each other, and this is wonderful!

Roughly 90% of humans are right-handed, and this is one of the traits that separates us from most other primates, who don't really show any general left- or right-handed preference.

Right hand and evolution

Right-handedness is believed to play an important role in human evolution. A recent study of the earliest evidence of right-handedness in the fossil record sheds light on when and why this trait arose. Interestingly, the evidence was found not in the hands of our ancient ancestors, but in their teeth.

It has long been known that the human brain consists of two approximately identical halves. The left hemisphere controls the ability to move and speak, while the right is responsible for visual-spatial attention.

It is also well known that lateralization, that is, the predominance of certain cognitive processes in one part of the brain, is distinctive feature human and is associated with improved cognitive abilities.

Could right-handedness play a role in brain lateralization? Ancient stone tools made and used by our early ancestors give us some clues.

Using Tools

The earliest stone tools date back to 3.3 million years. They were found in the territory of modern Kenya (Africa). Stone processing required high level dexterity. Scientists know from experiments that the left hemisphere of the brain, which is responsible for planning and executing actions, is active during this process.

At the same time, people overwhelmingly rely on their right hand when we're talking about about creating tools, compared to other activities. This is most likely because the left and right hemispheres control actions on opposite sides of the body.

While this relationship is not as simple as it may seem, in most cases, right-handedness and brain lateralization go hand in hand.

Object of study

So why did scientists decide to use teeth to study right-handedness? The answer lies in the dearth of left and right hand bones in the fossil record, especially those belonging to our early ancestors.

Without matching the set of left and right hand bones, it is impossible to study differences in size and shape to determine which hand our early ancestors used to perform tasks.

The teeth, on the other hand, tend to be relatively well preserved and may even have scratches that indicate right or left hand use.

Study of Neanderthal teeth

In an earlier study, scientists noted grooves on the front side of teeth belonging to European Neanderthals. They suggested that these grooves appeared when Neanderthals held the material in one hand and pressed it between their front teeth to work with stone tools, which could sometimes damage the teeth.

In experiments in which participants used mouthguards, these actions were copied. The results showed that oblique grooves appeared on the right side of the teeth when the material was held with the left hand and struck with the right. Therefore, oblique grooves are a good indicator of the use of a particular hand.

Study of the jaw of Homo habilis

The subject of a new study - an ancient upper jaw - is the oldest evidence of right-handedness in our genus Homo. This jaw belonged to one of our earliest ancestors, Homo habilis, who wandered from Tanzania to Africa about 1.8 million years ago. The jaw was found in the Olduvai Gorge of the Serengeti Plain, which preserves some of the world's earliest archaeological artifacts.

Marks on teeth

Interestingly, almost half of all grooves were on the right side of the teeth. Right oblique grooves were particularly common on the four anterior teeth (central incisors, right second incisor, and right canine).

This led the authors to believe that most of the grooves were made by the person's right hand. They also suggested that the four front teeth with big amount right oblique grooves were most often used during material processing.

The jaw of Homo habilis has important, as it provides the oldest evidence of right-handedness in the fossil record. But it also suggests that the basic level of brain organization appeared in humans at least 1.8 million years ago.

This brain development allowed us to learn important early skills, such as making stone tools, and potentially paved the way for the development of language. So being right-handed means a lot more to us than just a preference for using one hand.

» article « Why are there right-handed people?» Where we will try to answer in detail - with illustrations, examples and explanations. By the way, we have already touched on right- and left-handed cats on the site in the article “Right- and left-footed cats and kittens.”

Why are there right-handed people? At first glance, this is a strange question - everything exists. Just like lefties, in general. But if you take a closer look... Indeed, why are people mostly right-handed? WHY - what is the reason for the dominance of the right hand? After all, there are usually no accidents in nature...

Indeed, the existence of right-handers is by no means accidental. Read on to learn more about the patterns of right-handedness.

And let's start the story with an elementary truth: there are right and left halves of the brain. They correspond to the right and left halves of the body.

Let's move on to something less known and more mysterious: the left hemisphere of the brain controls the right half of the body, and the right hemisphere controls the left.

The nerve pathways from each hemisphere cross. What's the point?? It seems that direct control: the right hemisphere - the right half of the body - is more logical. Good question, and a detailed answer will be published soon - in the article “Why bilateral symmetry?”

It is also believed that the two halves of the brain are responsible for different abilities.

Right hemisphere:

• spatial-visual perception
• creates a holistic visual picture;
• it controls rough movements,
• responsible for intuition
• for emotional perception,
• with its help we perceive music.

The left hemisphere is in charge

• semantic perception,
• speech,
• by letter,
• account,
• analytical skills,
• abstract thinking,
• it is capable of creating false statements.

And again, the question is: what is the meaning of such a division? Again, the answer has to do with the existence of right-handers.

In right-handed people, the left half of the brain is more developed, while in left-handed people, the right half is more developed. This is called "hemisphere asymmetry." The reason for the asymmetry is the features of the action, not the structure. That is, activity is primary - and only then the hemispheres become asymmetrical.

The brain, which ensures the coordination of processes in the body, must perform two tasks:

• store information about accumulated skills
• and gradually master new functions.

It so happens that the role of conservation is played by the right hemisphere, and the role of mastering new tasks is played by the left hemisphere (in right-handed people). In other words, control of any new skill is first mastered by the left hemisphere. Once its “brain support” has been polished and consolidated, the left hemisphere transfers this control to the right.

That is, when you learn to do a backflip (play the piano, drive a car, etc.), until you learn it, one hemisphere is working. And when you learn, it’s different.

It has been noticed that new semantic sounds in humans are better perceived by the right ear, and flashing written words and numbers (new concepts!) are better distinguished by the right eye. We can say: the left hemisphere is a “nursery of new functions.”

Let's prove the theory about the different functions of half-rushes on monkeys.

Chimpanzee offered to remove the hook from the lid of the box and take out the treat. So, it turns out that the hook was pulled back more often with the right hand (this is a new thing, there are no hooks in the jungle), and the food was more often taken with the left (a familiar thing, practiced over centuries).

Similar results when observing gorillas. It turned out that when taking a vertical position and starting to move on their hind limbs, these monkeys more often lean on the ground with their right hand. Walking upright is a new skill, therefore, the right hand should help you master it!

This is why people experience the phenomenon of right-handedness. We perform a huge set of actions that our ancestors did not have. Chimpanzees don't fence and gorillas don't type. All these are late evolutionary acquisitions - and, therefore, first of all, the right hand and the left half of the brain deal with them.

Why are most vertebrates not right-handed or left-handed?

Because human right-handedness is associated with a load on the left hemisphere - the processing of new skills approximately from the Paleolithic (the beginning of tools), which are not characteristic of animals.

A few important words about left-handed people

In a few percent of cases, children are born whose genetic control over various functions of the hemispheres is altered. To put it simply, their hemispheres seem to change roles. The right becomes “revolutionary” and the left becomes “oppositional”. As a result, the child becomes left-handed. Retraining him to be right-handed in this situation is not just a pedagogical mistake, but crime , since when performing functions imposed from above that are unusual for the hemispheres, children often develop severe neuroses.

So, all new features and skills are first processed by the left hemisphere and then reinforced by the right.

You may ask: “Yes, why does one hemisphere dominate, this is understandable - different tasks”

“But why RIGHT-HANDED?”

“Why not the other way around, why are it not left-handed people who dominate?”

It’s all very simple - for the same reason as the need to touch exposed wires with the right hand: the right hand is further from the heart, and if a person sticks it in some nasty thing, he is less likely to die :)

returning to different tasks hemispheres: look again at the “abilities” of the two hemispheres. And pay attention: the dominant hemisphere is responsible for “recent” skills - speech, writing, logic. And the subordinate hemisphere is for the more ancient ones - emotions, intuition.

This is how it happens...

Illustration copyright Thinkstock

Around the world, right-handers make up the majority of the population. But why? – the correspondent wondered.

We humans don't often agree on opinions, but to at least one question the majority will give the same answer - which hand is more comfortable to use. If you write with one hand, then you probably eat with it, and for most people - about 85% - this is the right hand. In addition, “there is no historical record of left-handed people being dominant anywhere,” says archaeologist Natalie Uomini of the University of Liverpool.

Lateralization in limb use—that is, a preference for the left or right arm or leg—is most often explained by features of the brain. It is known that the left hemisphere is responsible for some tasks, while others are controlled by the right. However, everything is complicated by the fact that the nerves connecting the brain to the body intersect, so that the left hemisphere is in to a greater extent controls right side bodies and vice versa. In other words, with the help of the left hemisphere of the brain we use the right hand, eye, leg, and so on.

Some scientists believe that this neurological "division of labor" has existed in the animal kingdom for half a billion years. It may have evolved because the brain processes information more efficiently when the hemispheres perform various jobs. For example, we can assume that the left half of the brain solved everyday problems, say, searching for food, while the right always remained alert in order to notice and quickly respond to unexpected changes in the environment, in particular the approach of a predator. Confirmation of this - different kinds fish, toads and birds, which are more likely to grab prey visible with the right eye.

It turns out (although it is not so easy to prove) that when our hominin ancestors (the so-called hominin tribe traditionally includes humans, chimpanzees and their extinct ancestors - Ed.) began to walk on two limbs instead of four and their hands were freed up for new job, such as tool making, they were predisposed to use their hands differently. Or, as Stephanie Braccini and her colleagues put it in an article in the Journal of Human Evolution, "the development of individual asymmetry may have begun as early as early hominins habitually adopted an upright posture while using tools or foraging for food."

In an effort to confirm their theory, Braccini and her colleagues observed chimpanzees and discovered that when standing on all fours, the monkeys used both hands equally. The asymmetry in hand preference only appears when they have to straighten up to do something - but the monkeys are equally left-handed and right-handed.

In this case, there must be some other explanation for the fact that early people, who equally often preferred one or the other hand, were replaced by modern man- almost always right-handed.

We know approximately the era when this happened: scientists, as part of an experiment, tried to independently make ancient stone tools by cutting stone with their left or right hand and then comparing the resulting objects with those that remained from early hominins. As a result, we still have little evidence in favor of the right-handedness of our ancestors, who created tools two million years ago or more.

However, stone tools found at the Koobi Fora site in Kenya were made one and a half million years ago by representatives of two species that preceded humans - Homo habilis(“skillful man”) and Homo erectus(“homo erectus”) - already allow us to talk about a tendency towards right-handedness on the scale of an entire species. By the time the species appeared Homo heidelbergensis(“Heidelberg man”) about 600 thousand years ago, right-handed people already clearly dominated prehistoric society. Thus, the nature of wear of the remaining teeth Homo heidelbergensis shows that food was usually brought to the mouth with the right hand.

So, we found out when the skew to the right began, but we didn’t find out why. There is a version that this is due to language. Just as most of us are right-handed - and the left half of the brain, as we remember, is responsible for the right side of the body - in the same way, for most people, the left hemisphere is responsible for speech. This type of asymmetry is even more common than right-handedness; it can be assumed that as language specialization of the left hemisphere developed, the right hand began to dominate simply as a side effect. This is the so-called hypothesis Homo loquens(“human speaker”): lateralization of brain functions as a whole manifested itself under the influence of a person’s ability to walk on two legs and maintain an upright posture, and the preference for the right hand arose later, as the ability to speak developed.

Thus, universal right-handedness can only be accidental side effect the brain structures of most of us. But proving this hypothesis is difficult, if not impossible, because ideally it would be necessary to conduct a series of neurological tests on our ancestors, who are long dead. It turns out that we will never know for sure what sequence of events led to our species relying so heavily on the right side of the body and, by extension, the left side of the brain.

What can you say to left-handed people? Cheer up! As the authors of a study published in 1977 by the journal Psychological Bulletin noted, there is "extremely little evidence for a suggested association between left-handedness and any handicap." Moreover, a number of studies have shown that left-handers recover faster from traumatic brain injuries. And in battle, on the side of those who are good with their left hand, the effect of surprise is on the side - which means that left-handed people have an advantage in combat sports.

All this suggests that you can always find your advantages in deviations from the norm.

Psychologists identify some qualities of left-handed children, which in most cases distinguish them from right-handers:

Left-handed children are usually much more stubborn than their right-handed peers, and their period of stubbornness is protracted.

Often such children are artistically gifted; they draw well and with pleasure, and sculpt from plasticine and clay.

Many left-handers have good musical abilities and absolute pitch.

Many of these children begin to speak later than their peers and also have difficulty pronouncing certain sounds.

Sometimes problems arise with writing, reading and mathematics.

Left-handed children are spontaneous, trusting, and easily influenced by momentary feelings and moods. Hence - tearfulness, capriciousness, susceptibility to rage and anger, persistence in fulfilling desires.

But psychologists emphasize that left-handedness is not a pathology, but an individual version of the norm.

Reasons for the differences

If the left (it is responsible for the right part of the body), then such a person is right-handed, and if the right part of the brain dominates, which is responsible for left side body, the person becomes left-handed.

Scientists have identified degrees of dominance: strongly expressed (“one hundred percent” right-handed or pronounced left-handed) and weakly expressed (there may be 1-2 signs of “left-handedness”: the dominant left eye and left ear, but the leading hand is the right).

Each hemisphere of the brain is responsible for specific human abilities.

Why is he like this

Modern science identifies four main causes of left-handedness:

Genetic feature. Right hemisphere dominance is inherited. And not only from parents to children, but also through a generation, that is, from grandparents to grandchildren, and sometimes to great-grandchildren.

Birth injuries or pregnancy pathologies latest dates, which affected the development of the child’s brain. But it will be very difficult for such children. After all, it will be equally difficult for them to use both their right and left hands. Delays in speech, mental and physical development, motor impairment. Classes according to a specific program with a neuropsychologist and speech therapist will come to the rescue.

"Forced left-handedness." Occurs most often due to injury to the right hand at an early age.

Imitation. It happens that a child simply imitates, for example, one of his left-handed parents, and as a result, left-handedness becomes a habit.

Why you can't retrain

By retraining left-handedness, we are unsuccessfully trying to remake the biological nature of the child. We can force a child to write and eat with his right hand, but we cannot change the leading hemisphere of the brain.

What problems can you encounter when retraining a little left-hander? Your baby can get a wide variety of signs of neurosis. This may include blurred vision, abdominal pain, enuresis, various sleep disorders, changes in appetite, headaches, and stuttering. These disorders can manifest themselves either individually or in combination. In addition, retraining is fraught with the fact that your child will do poorly at school and, as a result, at the institute, he will have problems at work.

Looking for confirmation

So, your child writes, draws and eats mainly with his left hand - can we call him left-handed based on these signs? If you answer yes, it will not be entirely true. After all, a real left-hander is one who not only left hand, but also the left eye and left ear are superior to the right.

Give your child a little test.

So, you have already dealt with the definition of a hand, because the baby picks up objects, writes and draws more often with his left hand. Now let’s determine which ear he uses as the dominant one. Ask him to hold the alarm clock with both hands and listen to the clock tick. See which ear he puts them to. This makes it easy to identify the leading eye. Roll a piece of paper into a tube and give it to your baby in both hands. Offer to look through this “spyglass” for various objects.

Surely the sheet will be brought exactly to the dominant eye. Pay attention to which leg is more comfortable for your baby to jump on and which leg he kicks the ball with. These tests should be done around age five because children under five can use both their right and left hands equally often.

We help you develop

The leading hand of a left-handed child must be developed from childhood. IN game form it's easier to do this. Invite your baby to press his palm tightly to the table and lift each finger off the surface in turn - let the fingers alternately look up and lie back down. And any other exercise for developing a child’s motor skills will undoubtedly be beneficial.

To make learning the alphabet easier, you should rely on creative thinking. For example, the letter “F” looks like a tasty pretzel or glasses, and “X” is a walking man, “H” is an upside-down chair. Let the child come up with other associations himself. And so with each letter. It will turn out funny and useful game. It happens that left-handed children write letters in the wrong direction when writing, that is, they “mirror” them. In such cases they will help special exercises. Choose the letters that your baby “mirrors” and write them in a row yourself, with several letters in this row written in the wrong direction, the way the child usually writes them. Let him find the “mirror” letters on his own.

Handwriting in left-handed children is slanted to the left or may not have it at all.

It is important to remember that when doing activities related to writing, the light should fall on the left for right-handers, and on the right for left-handers.

Help your left-handed child position his hand correctly when drawing and writing with his left hand. The baby’s hands should lie on the table so that the elbow of the left hand protrudes slightly beyond the edge of the table and the hand moves freely along the line, while the right hand lies on the table and holds the sheet. The left hand should be facing the table surface. The fulcrum points for it are the nail phalanges of the slightly bent little finger and ring finger, as well as the lower part of the palm.

The fountain pen is placed on the upper, nail part of the middle finger, and the nail phalanges of the thumb and index finger hold it at a distance of 1.52 cm from the end of the rod. In the process of writing, a left-handed person moves from left to right (the direction of the pen is to the left, and the movement of the hand and fingers is to the right). The left hand with the handle is located under the line. This is the most convenient way of writing, since the child does not have to twist his hand, the sample is clearly visible, and what was previously written does not become blurred. Naturally, the letters will be written slanted to the left. In this case, the notebook lies tilted to the right, the lower right corner of the page is directed towards the middle of the chest.