Men Born During Winters More Likely To Be Left-Handed, Study


Men born during winter months (November, December and January) are more likely to be left-handed than those born during rest of the year, according to a University of Vienna study.

For the study, psychologists surveyed 13,000 adults and found that 7.5 per cent of women and 8.8 per cent of men were left-handed. Among men, 8.2 per cent of the left-handers were born during February to October. This figure rose to 10.5 percent between November and January.

Researchers claim that the increase percentage of left-handedness in men could be related to hormonal factors. It is believed that embryo's exposure to higher levels of the male hormone testosterone in the womb increases their chances of being left-handed.

Researchers said that more daylight exposure may increase testosterone levels. Baby boys born during winters are in the embryonic stage during the spring and summer. As a result, they are more likely to be associated with increased daylight exposure and testosterone levels.

"Presumably, the relative darkness during the period November to January is not directly connected to this birth seasonality of handedness. We assume that the relative brightness during the period May to July, half a year before, is its distal cause," Lead author of the study, Ulrich Tran, said in a statement.

The effect is prominent in men than women because male brains are exposed to considerably higher testosterone levels than female brains during prenatal development. The testosterone levels are higher in the male foetus because of its own testosterone secretion than in the female foetus.

The finding is published in the scientific journal Cortex. 

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