However, post-hoc exploration of their and other sets of data has shown that there is an apparent tendency for left-handedness to be more prevalent in the period March-July than in the period August-February. The present work tested this seasonal hypothesis prospectively among university students.
A meta-analysis published in 2008, based on data from more than 40,000 participants, found primarily that left-handed men had a slight tendency to have been born from March–July (in the northern hemisphere)51.
While the genetic bases of handedness are still under debate, scientists obtained indirect evidence of a hormonal mechanism promoting left-handedness among men. Men born in November, December or January are more likely of being left-handed than during the rest of the year.
Hand preference probably arises as part of the developmental process that differentiates the right and left sides of the body (called right-left asymmetry). More specifically, handedness appears to be related to differences between the right and left halves (hemispheres ) of the brain.
In a study from 1975 on 7688 children in US grades 1-6, Left handers comprised 9.6% of the sample, with 10.5% of male children and 8.7% of female children being left-handed. Handedness is often defined by one's writing hand, as it is fairly common for people to prefer to do a particular task with a particular hand.
McManus which found that the Netherlands has one of the world's highest prevalences of left-handedness at 13.23 percent. The United States isn't far behind with a rate of 13.1 percent while neighboring Canada has 12.8 percent. Elsewhere, rates of left-handedness are far lower and China is a good example.
Left-handed people are said to be good at complex reasoning, resulting in a high number of lefty Noble Prize winners, writers, artists, musicians, architects and mathematicians. According to research published in the American Journal of Psychology, lefties appear to be better at divergent thinking.
For example, if both parents are right-handed, there is a 1 in 10 chance of having a left-handed child. If the father is left-handed, the odds are 2 in 10. If the mother is left-handed, the odds rise to 3 in 10.
Left-handedness occurs in about 8% of the human population. It runs in families and an adoption study suggests a genetic rather than an environmental origin; however, monozygotic twins show substantial discordance.
In their analysis of 144 handedness and brain laterality studies—accounting for a total of nearly 1.8 million individuals—University of Oxford psychologists Marietta Papadatou-Pastou, PhD, and Maryanne Martin, PhD, found that males are about 2 percent more likely to be left-handed than females.
The "highest risk" group is said to be those who are first born to older mothers (aged 30 or over) (Bakan et aI., 1973).
Eleven percent of the population is born left-handed, and if they seem different, it's because they are! Learn six tips for raising a left-handed child.
Left-handers or lefties are often considered unlucky in many cultures, including the Indian culture. We are told to accept prasad with our right hands only, and this hand is preferred for all our rituals, tilak, yagna, etc.
If both mother and father were right-handed, the chance of their offspring being left-handed was only 7 percent. However, if one parent was left-handed, the chance of the offspring being left-handed, too, was 21.4 percent, more than three times as much as for two right-handed parents.
Researchers who study human hand preference agree that the side of the preferred hand (right versus left) is produced by biological and, most likely, genetic causes.
The “American Heritage Dictionary of the English Language” cites the conventional wisdom that the word “southpaw” originated “from the practice in baseball of arranging the diamond with the batter facing east to avoid the afternoon sun.
The Queen herself is right-handed, but this was not the case for her parents. The Queen Mother was left-handed, as was the Queen's father, King George VI, but his father King George V is believed to have made him write with his right hand.
Queen Victoria is one of the most famous historical lefties. Although she wrote with her right hand, she painted with her left, which indicates she was made to switch as a child, as was sadly common in the Victorian era.
Lefties can also use their status strategically in sports. They have an advantage in tennis, baseball and boxing, for example, because righties have a tough time predicting their less familiar moves. Lefties also have their own special day on the calendar.
If the parents are both right-handed, in dizygotic and monozygotic twins there is a 21% chance of one being left-handed. If one parent is left-handed, in DZ and MZ twins there is a 57% chance of one being left-handed. If both parents are left-handed, it is almost certain one twin will be left-handed.
On the flip side, lefties have some disadvantages too.
Some studies show that left-handed people showed an imbalance in processing emotions with their left and right hemispheres of their brain. Left-handed people have a higher risk of brain disorders like schizophrenia, dyslexia or hyperactivity disorders.
Being a leftie has a genetic component, is linked to better verbal skills and is associated with a lower risk of Parkinson's disease, according to a new study published in the journal Brain.
But handedness has its roots in the brain—right-handed people have left-hemisphere-dominant brains and vice versa—and the lefties who claim Einstein weren't all that far off. While he was certainly right-handed, autopsies suggest his brain didn't reflect the typical left-side dominance in language and speech areas.