Left - handedness prevalence in the development and function of the left hand over the right, usually congenital. Left-handedness may be hidden when southpaw learned how to use mainly the right hand. In a critical situation that requires quick and subconscious (reflex) actions hidden left-handedness may manifest attempting to perform this action with the left hand. And this is when handling devices, instruments I so on, designed for right-handed, sometimes dangerous (parachutists, pilots, drivers and other). Sneaky left-handedness can be detected by some signs: left hand more and nails wider, with an interlacing the fingers of both hands on top of lies I finger of the left, not the right hand. Leading eye with left-handedness is left, that when the army does not allow marksmanship from the right shoulder. Children with left-handedness sometimes start to speak later than they should, otherwise develop normally and mentally and physically. Violent, with reproach and ridicule, "retraining" child-left-handed often leads to his nervousness, stuttering, etc., But to write with the right hand, many left-handed people get used to it easily.
Left-handedness is purchased (for example, after a crippling injury of the right hand); victim to save the old profession may require tools that are specifically adapted to the left hand."

Left-handedness may be congenital (sometimes hereditary and forced - due to violations of the right hand. Distinguish between left-handedness explicit and hidden; when the last man, being born left-handed, by training accustomed to use mostly the right hand. Left-handedness, as well as right-handed and equal development of both hands (ambidexterity), depends on various environmental conditions of the origin and development of man. In our environmental conditions left-handed is 3 % of the total population.
Out of 100 children at the age of 7-8 months. (the time of development grasp reflex) in three celebrated left-handedness. The percentage of left-handed in other parts of our planet varies to a large extent (for example, Australians he reaches 26%, and the residents of South Africa is even more). The asymmetry of the structure on the globe concerns not only man, but of all living creatures and plants - crowns, root system and annual rings, clearly visible on the transverse end of the trunks of trees.
Sneaky left-handedness can be identified by a larger value of the left hand do left-handers, further development of the veins in the rear of the left hand, the greater the transverse size of the nails, more Mature facial muscles on the left, the movement of hands during work.
Clenching brushes with intertwined fingers, the thumb of the left hand is on top; when apadravya more active the left hand is on top. When walking in a straight line with a blindfold left handed immediately stray from the straight line left to right and right-handers Vice versa.
The prevailing development of the left half of organisms is connected with change of a direction of movement of living beings. Left-handedness, right-handed and ambidexterity by some authors regarded as hereditary characteristics. Left-handedness may be one of the twins. In countries where a large percentage of left-handed, schools write alternating right and left hand (Australia and others).
Among left-handed often persons who write in the mirror right to left - left hand and left-to-right is right, and sometimes I write the lines vertically.
The left-handed two of speech center is one in the left, and the other in the right hemisphere, in hemorrhages in one of them there comes a more rapid compensation of speech development. Left-handed, as a rule, have left leading eye and left a leading ear, unlike right-handed. They badly hit the target when firing, if the aim with the right eye, and well shoot, if the aim with the left. The re-education through labour, physical education develops the parties to any limit, but the prevailing party in left-handed individuals is still left. In the education should not oppress baby violent regime of re-education of left-handed to right-handers. The child and without such education perfectly adapts to the environment, labour and mechanisms of instruments of production. This is considered and schools in those countries where the percentage of left-handed relatively high.
In several countries (England, Japan, China) produce the instruments of production and for left-handed.
Violent upbringing and accusations against left-handed child can sometimes cause a change of mentality, nervousness, rhythm of life, speech, stuttering. Impure speech with unclear pronunciation of the letter "p" is more common among left-handed, as well as color blindness, strabismus and Hesse epilepsy. Left-handed children often start to speak later, but not lag behind the right-handed.
Practice shows that left-handed people are accustomed to do any responsible manipulation right hand, in a critical situation can suddenly appear prevalence left. This especially applies to protective actions, as unconditional reflex makes hidden Lefty act left hand. This should be taken into account, especially in the selection of paratroopers; it is necessary to accurately establish the reliability of Lefty acquired reflex when pulling rings, parachute, the location of which is designed for the enjoyment of the right hand. When flying a plane, driving a car, at work on the control panels, designed for right-handed, quick resourcefulness and orientation, left-handed without sufficiently secured exercise of the right hand can also make mistakes.