Despite the fact that people who write with their right hand are sometimes considered left-handed people, this is not entirely true. A left-handed person is the one who has the leading or dominant left hand. In this case, the person will perform all basic actions with it, even if the school taught them to write with their right. About 10% of the population is left-handed and this explains the impressive amount of research on this topic. Take a look at what science knows about our leading hand.
Left-Handedness and Genetics
Many animals prefer one side of the body. Seven out of ten chimpanzees are right-handed but almost all kangaroos are left-handed. As for humans, preferences in the sense of the right or left hand are formed in the eighth week of pregnancy and from the thirteenth week, the fetus prefers to suck on either the right or left thumb. Children finally determine their leading hand at about the same time that they learn to speak, at the age of about four years.
Genes can affect right-handedness and left-handedness, but not much. Scientists have found at least one PCSK6 gene which is associated with the transformation of a ball from identically oriented cells into an embryo with distinguishable right and left sides. But the fact that 25% of children with both left-handed parents will act mainly with the left hand allows us to talk about the significant influence of upbringing, environment, and other non-genetic factors.
Researchers at Birmingham University found that the person’s leading hand affects how fast you understand sign language. Absolutely all people who speak sign language respond faster to the information provided by the right-hand. But if you look only at the signs in which both hands are involved, then left-handed people will be more understandable.
The Myth About Genius
The penchant of left-handed people for creativity is a myth based on a 1995 study. It showed that left-handed people scroll more options for solving the problem in their heads but this has nothing to do with creativity. As for the speed of information processing, new studies show that there is not a big difference between left-handed and right-handed people. Cognitive abilities and language development are comparable for both.
Scientists also found that 64% of men and 73% of women hold their children with their left hands. Science suggests that it is all about emotions that are processed in the right hemisphere of the brain associated with the left hand. On the other hand, the need to free the right hand for the convenience of related activities also cannot be excluded.
Do Ambidextrous People Really Exist?
People who are able to perform actions of the same complexity with the same speed and efficiency are called ambidextrous. Such people are extremely rare because there are no more than 1% of them in the world. The rest of the data regarding ambidextrous require further verification. But if you are still interested, then know that they are more likely to report bisexuality and are easily affected by the emotional influence of a group.
Given the unusual nature of the phenomenon, mankind knows surprisingly little about its causes. Statistics show that the older a person is, the more inclined they are to being ambidextrous but only because with age it becomes more difficult to cope with usual affairs with one hand.
Is it true that an ambidextrous person is better at learning? Scientists are not entirely sure, despite the existence of the theory of neuroplasticity. On the contrary, there is evidence that ambidextrous do worse with some cognitive tests than lefties and righties. Another study suggests that ambidextrous may be associated with a stronger age-related decrease in brain volume.
Pros, Cons, and Pitfalls
In 1996, researchers at Harvard Medical School found that orthopedic surgeons, librarians, and mathematicians were mostly right-handed, while lawyers and architects were more likely left-handed. A quarter of the Apollo space program astronauts mostly used their left hand, so perhaps left-handed people have an inexplicable craving for space.
Left-handed people are less prone to arthritis, ulcers and are able to recover more quickly from strokes due to a lower susceptibility of the brain to damage typical for such diseases. Left-handers are less likely to get into car accidents and generally drive more carefully. They are better suited to highly competitive conditions.
There is more disturbing evidence. When researchers from Yale University interviewed patients in a psychiatric clinic, 40% of those who were diagnosed with schizophrenia or schizoaffective disorder admitted that they wrote with their left hand. A recent study showed that left-handed people have a higher risk of cancer and more often contact primary care physicians about serve health problems. They are more often diagnosed with different sleep disorders.