Scientists have linked artificial feeding with left-handers
Once the person is right-handed or left-handed, affects the type of feeding in the first year of life, American scientists have found. Among those who were bottle-fed, left-handers was greater than among those who were breast-fed. This may be due to the hormones that are produced in breast-feeding mother and child.
The child receives nourishment in the first year of life — from a bottle or is breastfed, influences what he will be left-handed or right-handed, discovered epidemiologists at the University of Washington Philip Jewel. The study was published in the journal Laterality: Asymmetries of Body, Brain and Cognition.
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The researcher conducted a meta-analysis of seven works from Ireland, Australia, USA and other countries, covering more than 60 thousand infants born in the years 1951-2011 and their mothers.
It turned out that among children who were bottle-fed, left-handers than among those who were breast-fed.
Of course, this does not mean that artificial feeding will make the child left-handed — in the end, the tendency to use a particular hand is determined mostly genetically. However, apparently, the type of feeding can affect the expression of natural inclination.
Jewel together with the lateralization of the brain — process in which various mental functions associated with the left or right hemispheres of the brain. Laterality in humans is right up to the end of adolescence.
“I believe that breastfeeding optimizes this process,” he said.
After studying the data on children whose mothers were breast-fed, the researcher found that the number of left-handers among them every month decreased and reached a plateau for 9 months.
So, breastfeeding for one month reduced the number of left-handers compared to children who were bottle-fed, 9% within six months — by 15% within 9 months — 22%. Longer breastfeeding has not led to any difference.
Jewel believes that the first 9 months of life most critical to highlight the dominant hand of the child. In addition, he found that the twins have a chance to become left-handed higher — perhaps because they have to share mother’s milk. Among the preterm infants, which in hospitals is bottle-fed, the number of left-handers also appeared to be higher:
Perhaps, the influence of breastfeeding on the right – and left-handedness is associated with a type of power not directly but indirectly through hormonal responses that occur in the body of the mother and the child during feeding.
He does not exclude that there is some significant factor that he did not realize.
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In the end, no matter right-handed or left-handed will increase the child — the main thing that fed well. But the interrelation of interest for further study of how the brain is formed in the first years of life.
Also Jewel cites the findings of a number of other works over the last 20 years, where, in addition to the link between the type of feeding and the dominant hand, there were other correlations. Thus, children who were breastfed, intelligence is higher, head circumference — and more rarely, problems with speech than those who were bottle-fed. Also those who were breast-fed, in the future less likely to develop multiple sclerosis. Such differences presumably are attributable to biological factors, breast-feeding leads to an increase in the volume of gray matter and myelination of neurons (the formation of myelin sheaths required for the interaction of nerve cells). However, this hypothesis is disputed.
Hewel notes that over time among boys becomes more left — perhaps this is due to a reduction in the duration of the breastfeeding period. In developing countries, such as India, the trend is the opposite — where girls are weaned sooner than boys.
Ignoring such factors as breastfeeding, may lead to the wrong conclusions when assessing the changes in the number of righties and lefties, warns scientist.
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People will be left-handed or right-handed, can be determined at 18 weeks of fetal development, found in 2017, researchers from Italy. The scientists observed with the help of 4D ultrasound in 29 of the fruits in the womb at different stages — on 14,18 and 22 weeks. Analyzing the 20-minute recording hand movements of the fetus in side of the mouth, eyes and the uterus, they make predictions about what hand the child will primarily use in the future. Nine years later they found out, who from children have grown up left-handed and who is right-handed and to compare the obtained results with earlier observations. As was made after 18 weeks, the predictions were true at least 89%.
The results confirm the hypothesis that left-handedness and right-are predefined at the stage of fetal development. The accuracy of the analysis opens new perspectives for doctors preference for a particular hand is associated with abnormalities, including megalochary asymmetry, depression, schizophrenia and autism spectrum disorders. Monitoring of the fetus will allow us to identify the possibility of such deviations and to think over in advance strategy of interaction with the child.