Winter babies, especially men, born between November and January are more likely to be left handed, a new study has claimed.
Various manual tasks in everyday life require the use of the right hand or are optimised for right-handers. Around 90 per cent of the general population is right-handed, only about 10 per cent is left-handed.
The study by Ulrich Tran, Stefan Stieger, and Martin Voracek from the University of Vienna comprised two large and independent samples of nearly 13000 adults from Austria and Germany.
- Mumbai’s Haji Ali Dargah Trust to SC: Ready to give women access to sanctum sanctorum
- Samajwadi Party Crisis: 5 Quotes By Mulayam Singh Yadav At Press Conference
- Ae Dil Hai Mushkil Vs Shivaay: What Delhites Pick
- Supreme Court Directs Vijay Mallya To Fully Disclose Foreign Assets In 4 Weeks
- 5 Reasons To Watch Ae Dil Hai Mushkil
- BSP Supremo Mayawati Criticises PM Modi Over Triple Talaq: Here’s What She Said
- Google Pixel XL Phone Review: Pros, Cons And Final Verdict
- Defence Minister Manohar Parrikar Says Army donation Is Voluntary
- Rock On 2 Trailer Launch: Farhan Akhtar, Shraddha Kapoor, Prachi Desai On Their Roles
- Cyrus Mistry’s Career Timeline
- Stalker Kills Woman At Metro Station In Gurgaon: Here’s What Happened
- Bigg Boss 10 October 24 Review: Seven Contestants Nominated For Evictions
- Power Struggle In Mulayam’s Party: Here’s What People Reacted
- 1 Dead, 5 Injured In Low Intensity Explosion In Delhi’s Naya Bazaar Area
- Delhi: Naya Bazar Explosion Cctv Footage
Overall, 7.5 per cent of women and 8.8 per cent of men were left-handed.
“We were surprised to see that this imbalance was caused by more left-handed men being born specifically during November, December, and January. On a monthly average, 8.2 per cent of left-handed men were born during the period February to October. During November to January, this number rose to 10.5 per cent,” according to Ulrich Tran, lead author of the study.
“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,” said Tran.
A theory, brought forth in the 1980s by US neurologists Norman Geschwind and Albert Galaburda, posits that testosterone delays the maturation of the left brain hemisphere during embryonic development.
The left brain hemisphere is dominant among right-handers, the right brain hemisphere is dominant among left-handers. Intra-uterine testosterone levels are higher in the male foetus, because of its own testosterone secretion, than in the female foetus.
However, the testosterone level of the mother and external factors may also affect intra-uterine testosterone levels. Specifically, more daylight may increase testosterone levels, making a seasonality effect plausible.
Previous studies on the subject provided mixed and inconsistent evidence. There was no clear indication which season has an effect, and whether seasonality affects men, women or both sexes equally.
According to the current findings, there is a small, but robust and replicable, effect of birth seasonality on handedness, affecting only men.
These results are consistent with a hormonal basis of handedness, corroborating thus an old and controversial theory.