This is a person who is dominated by the right half of the brain.
Left-handed (left-handed) - a person preferably using the left hand. Among people, left-handers make up about 15%, that is, one in seven is left-handed.
Among the inhabitants of the Earth on all five continents of our planet, regardless of nationality and race, right-handed people prevail.
Unequal people should be divided into two unequal parts.
The majority are left-handers, people whose left hand is predominantly developed. If they were not retrained in childhood, with this hand they eat, write, wind the clock, hammer nails. Their left hand is stronger, faster, more reliable. But, the hand used to write is not an accurate indicator of left (right) handedness. For example, many left-handed people write with their right hand, using their left hand for most other tasks.
The smallest part includes ambidexters - people with equally developed arms. In fact, these are people with equally poorly developed hands. It is from their midst that subjects emerge who do not even know how to hammer in a nail and who, when trying to wash the dishes, it beats faster than it becomes clean. There are few such people, but, according to research by scientists, their number is constantly growing.
Humanity has never been entirely right-handed. The existence of left-handers has been reliably known since biblical times. After the return of the Jews from Egypt and their conquest of Palestine, the sons of the tribe of Benjamin, who later formed, together with the tribe of Judah, the kingdom of Judah, were distinguished by special militancy. In 1406 BC, 700 soldiers were selected from an army of almost twenty thousand, who knew how to throw stones from a sling with their left hand and accurately hit the target. Thus, even in those days, 3.7 percent of Jews were clearly left-handed. Considering that the diagnosis of left-handedness was hardly more accurate then than it is now, then we can assume that the ratio of left-handed and right-handed people has not changed significantly since then.
Scientists of the last century were quite well aware of the uneven development of our hands, but they took it too literally. Indeed, the muscles of the right arm are more massive, which means they have more strength. However, the coordination of muscle work depends entirely on the perfection of the command centers of the brain. It is not the right hand itself that is better developed, but the motor centers of the left hemisphere, which command it. It is more correct to speak not about the leading hand, but about the leading hemisphere of the brain.
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At the same time, one should not forget the peculiarity of the functional organization of our brain - cross-control of the muscular apparatus. Therefore, the work of the right muscles of the human body is controlled by the left hemisphere of the brain, and the work of the left muscles is controlled by the right hemisphere.
Thus, for right-handers, the left hemisphere is the leading, and for left-handers, without sufficient reason for this, the right was still considered the leading one.
How ambidextrous brains are developed is not known for certain. It is assumed that the most developed centers from any pair of command posts of the same name are randomly represented in the right or in the left hemispheres of their brain.
People have noticed their own asymmetry a long time ago. In several drawings of a prehistoric man, made about 30 thousand years ago, the hunters hold a spear or club in their right hand. This means that already at that time, most of our ancestors were right-handed. However, and until now we are absolutely unknown the reasons for the predominance of the right hand over the left. Of course, there are many guesses on this score, but now it is already obvious that most of them will have to be discarded.
In children under one and a half to two years, both hands are developed in exactly the same way. This circumstance gave rise to the idea that we create right-handedness in ourselves, raising our children accordingly. Even the ancient Greek philosopher Plato, the founder of the world's first academy, believed that through the stupidity of mothers and nannies who teach us to do everything with our right hand, we acquire this nasty habit and from harmoniously developed people, which we are born into, we turn into cripples. Even in our time, such ideas have their supporters.
It was suggested that right-handedness is brought up from the first days of a child's life and at first it is carried out by our parents unconsciously. Right-handed mothers (naturally, this applies equally to right-handed dads, grandparents) most often hold their children to the left, freeing their right hand. It was assumed that, being in this position, it is more convenient for the child to use the right hand. Thus, a constant posture at an early age should lay the foundation for right-handedness in a child.
The theories listed above do not seem convincing at present, but there are no others yet. It is only known for certain that the preferred development of one of the hands is in no way a consequence of upbringing, but is inherited. It is more convenient to trace this pattern on left-handed people.
In families where both parents are left-handed, 50 percent of children are also born left-handed;
16.7 percent of left-handed children appear in families where only one parent is left-handed;
6.3 in families of right-handed people.
It's amazing how we humans know little about ourselves. We still do not know exactly how many right-handers are on earth, and how many are left-handed. The corresponding calculations were carried out more than once, but their results rarely coincided with each other. Various scientists have estimated the number of left-handers from 1 to 30 percent.
In modern more detailed studies, figures from 5 to 20 percent are cited.
This inconsistency depends on the assessment methodology. It is important not only who the subject considers himself to be, how others evaluate him and which hand he mainly uses in everyday life, but also the results of performing special tests.
With their help, it is possible to reveal the hidden left-handers retrained in childhood. Most scientists now believe that although special training, especially started at an early age, can turn a left-handed person into a person who uses his right hand more often, retraining will not fundamentally change the features of the functional asymmetry of the brain.
To identify the leading hand, 5 … 10 special tests are used.
If, when the fingers are intertwined, the thumb of the right hand is on top, and the right hand is in the "Napoleon's pose" with the upper arms crossed on the chest, it is considered that the subject is right-handed.
In the applause test, right-handers slap the palm of their right hand against the still palm of their left.
When winding up the watch, they hold it in their left hand, and turn the crown of the winding mechanism with their right fingers.
The subject is given two pencils and, blindfolded, asked to draw two circles or squares. The leading hand drawing is much more perfect than the second drawing.
The value of these tests is in the consistency of results. The final conclusion is made on the basis of their totality.
For left-handers in diagnostic tests, everything turns out the other way around: when the fingers are intertwined, the thumb of the left hand is at the top, and in the "Napoleon's pose" the left hand.
Nothing definite can be said about ambidextrous. When performing tests to determine the dominant hand, these subjects give the most incredible discord. There are ambidextrous people who write and eat with their left hand, and wind up and gesture with their right hand.
A systematic study of motor asymmetry has revealed many surprising and still obscure details.
As already mentioned, in newborn babies, both hands are equivalent. If preferences in their use arise in the first years of life, then they are not long-term and can change many times. Only in the fifth year of life, the right hand of future right-handers gradually begins to take on all complex activities. The process of her improvement continues for a long time and ends in adulthood.
When - scientists cannot yet say.
It is assumed that in old age the opposite process occurs and the unequal value of the hands is gradually smoothed out. It is difficult to say whether this sequence is a normal process of development of functions or whether age-related brain pathology is to blame for smoothing motor asymmetry.
There is an idea that in girls and women the asymmetry of hands is less pronounced, and left-handers among them are 1.5 … 2 times less than among the stronger sex. Improving girls' brain functions takes a long time and takes place slowly.
In boys, at the age of six, many functions are performed separately by the right or left hemisphere of the brain, while in girls twice their age, brain specialization is often just beginning. Usually, the development of the left hemisphere is seriously lagging behind in comparison with the right one, and the improvement of the latter proceeds especially slowly, which determines the absence of pronounced asymmetry in girls in the first 6 … 10 years of their life.
It is especially interesting that among twins, left-handers come across much more often than among those born alone, and both twins are rarely left-handed. Usually one of the twins always becomes right-handed. If the twins are heterosexual, the boy becomes left-handed more often. Among Siamese twins, as a rule, one is right-handed, the other left-handed.
And what about the rest of the organs of our body?
Are they equally developed or, like arms, have different abilities?
In everyday life, we do not feel much difference. In leg development, for example, asymmetry is less pronounced than in arm development, and none of our lower extremities has such significant advantages as the right hand.
It is not surprising that there is still no complete clarity on this issue. Some researchers believe that the right-handed dominant leg has the left, more recent studies have shown that people with the right-handed dominant leg also becomes the right.
Lefties have not yet found a clear preference for any particular leg.
It is difficult to identify the leading leg. There are few special tests to answer this question. The nature of the asymmetry of the lower extremities is judged by how we sit cross-legged and by the relative length of the stride. It is believed that we usually throw in the leading leg and its stride is long.
Another sign is associated with this property of the leading leg - a deviation from a given direction when moving with a blindfold. Since the leading leg takes a longer stride, a person striving to walk straight, but not being able to control the direction of his movement with the help of vision, will deviate to the side opposite to the leading leg.
The systematic deviation from rectilinear movement explains why people who get lost in the forest or in high reeds and try to strictly adhere to the chosen direction, after making a large circle, eventually return to the place from which they began to move.
The functional asymmetry of the cerebral hemispheres is not limited to differences in the perfection of the muscle functions of the right and left halves of the body. It can also be found in the work of the senses. In humans, it is possible to detect the leading eye and the leading ear, the leading half of the nose and tongue.
The dominant eye in 62 percent of people is the right. If he becomes slightly blind and the person begins to use the other eye more often, the leading eye does not lose leadership.
Most people have more taste buds on the left side of the tongue, and it is more sensitive to taste stimuli than the right side.
In terms of sensitivity to olfactory stimuli, the left half of the nose is also leading. It is assumed that all olfactory information is analyzed by the right hemisphere, and the left hemisphere is completely uninterested in smells.
We easily recognize familiar objects by touch. Even a casual touch can tell a lot about them.
For right-handers, according to tactile talents, the left hand is the leading one. Its readings are more reliable. The left hand more accurately determines the temperature of the object, and the right hand understands its weight better. Asymmetry of tactile abilities occurs already in children. It was even found in six-year-old boys.
In right-handers, the right hand is slightly longer than the left, and the nail bed of the thumb is longer and wider than on the left hand.
The nose of right-handers deviates to the right, and of left-handers - to the left, the curl of hair on the head of a right-hander is twisted clockwise, and on the crown of left-handers in the opposite direction. The direction of the curl seems like a complete trifle, but for some reason so many different superstitions are associated with this feature of our hair.
Thus, most of the functions of the human body are expressed asymmetrically, and this indisputably indicates that the functions of the brain, in turn, are also unevenly distributed between the hemispheres. In other words, man is an extremely lopsided creature.
Boris Sergeev. "Mind is good.."