Left-handedness Depends On The Times Of Conception And Birth
Baby boys born in the winter time are more often left-handed than those born in the summer, the study found. Experts at the University of Vienna examined 13K adults. It has been proved that 7.5% of females and 8.8% of males were left-handed.
Moreover, 8.2% of men have been born left-handed in time from February till October. But 10.5% - in tme from November till January. Apparently, seasonality is related to the hormones level that determines left-handedness probability. It’s considered that a high level of testosterone on stage of the fetal development makes people left-handed. The longer the day, the higher is testosterone. Since babies born in the winter, whole summer are being in fetal development stage, they get more of the hormone.
Revealed effect explained the situation with men that initially had more testosterone, but not with women. Even though it is possible that external factors increase hormone levels when harboring girls. Generally, testosterone can inhibit the left hemisphere development. And this is the main hemisphere for right-handers.
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