"Left Handedness" By Allen Weiss, MD, MBA, President and CEO

Left Handedness

May 15, 2010 -Left handed people make up about 5% to 15% of the population.

They have included recent Presidents Truman, Ford, Reagan, George H.W. Bush, Clinton, and Obama. Other famous and infamous left handed people range from Joan of Arc to Jack the Ripper. (For more famous lefties: www.indiana.edu/~primate/left.html#Miscellaneous)

There is a long-standing fascination with left handedness that has “left” us with many customs and much history which most of us accept without a second thought.

  • The fourth finger on the left hand was thought to be directly connected to the heart, which is why this is now the finger for wedding rings.
  • Julius Caesar was left handed, which is why he instructed all his subjects to shake hands with their right hands—thus leaving his weapon hand unencumbered.
  • In olden times evil spirits were thought to lurk over the left shoulder. One method of ridding the evil spirit was to throw salt over the left shoulder. (Salt was a very valuable commodity, considered a form of money at the time.)
  • Napoleon Bonaparte, military general and self-proclaimed Emperor, was left handed, and therefore directed his armies to march on the right so he could keep his sword arm between himself and the advancing enemy.
  • Subsequently any area of the world settled by the French would have the “right of way” on the right side of the road.
  • Left sided driving as in England persists because in earlier times, most leaders were right handed and therefore felt more secure with their advancing potential enemies on their right.

Left handedness has been associated with evil: There are more than 100 biblical references to the right hand being used for blessings and goodness, while the left hand is associated with the devil and evil about 25 times.

There are many myths, some facts, and a few inconveniences about left handedness which may be more interesting to those of us who are left handed. We left-handed folks struggle with everything from handwriting to obtaining sports equipment. Phil Mickelson, the famous golfer is actually right-handed and plays left handed. He mirrored his father's swing as a kid. However, most right handed people never think twice about how the world has been set up for the majority of the population.

Left-handers were severely discriminated against during the 18th and 19th centuries and it was often “beaten out” of people. In adulthood, left-handers were often shunned by society, resulting in fewer marrying and reproducing. In the Middle Ages, writing with your left hand was punishable by death. As discrimination was reduced in the 20th century, the number of natural left-handers who stayed left-handed increased.

There are theories as to whether left handedness is inherited. One single gene called “right shift” directs a person to become right handed. Righties can receive a gene for this characteristic from either parent. If neither parent shares this “right shift” gene with their child, then there is a greater chance the child will be left handed. However, many left handed children are encouraged at an early age to become right handed so the expected number of left handed children based on genetics is somewhat less. If both parents are left handed, 50% of their offspring will be left handed. Two righties only have 2% chance of having a lefty. Twice as many men are left handed compared to women.

If your mother is left handed, your chances of being left handed increase. Children who had a difficult birth or low birth weight also have a higher incidence of left handedness. There is a high tendency in twins for one to be left-handed. These observations argue against genetics and more for an environmental cause for left handedness.

Another theory is that testosterone levels in early embryonic development may also play a role brain development which cause the right side of the brain to dominate. This in turn leads to the left side of the body becoming dominant.

Each half of the brain becomes specialized as a fetus develops—which makes sense, as we do not have an unlimited capacity or brain size. The part of the brain which controls hand function uses a relatively large part of the brain. Having both hands being equally dexterous would utilize a disproportionate amount of the brain's capacity, thus taking away from other potential functions. This theory explains why the majority of people are either right or left handed.

The bottom line is that there are probably multiple influences which account for which hand is dominant. It's also important to note that the brain is divided into two sides which do not function identically. Each side is responsible for the opposite half of the body. Normally the speech and language center is in the left side of the brain in right handed people. But even in left handed people the language center can be on the left side, thus making strokes in lefties slightly different than those from right-handers. (Left handed stroke victims recover faster than right handed stroke victims.)

Left-handers' brains are structured differently in a way that widens their range of abilities. Lefties are relatively more numerous among children rated as having an IQ higher than 131.

Left-handed university students are more likely to major in visually-based, as opposed to language-based subjects. One sample of 103 art students found an astounding 47% were left- or mixed-handed, according to Facts on Left Handed People.

There are other interesting advantages of being left handed, according to several sources:

  • Left-handed men are 15% richer than right-handed men for those who attended college.
  • And if they graduated from college, left-handed men are 26% richer.
  • Lefties excel in tennis where almost 40% of the top tennis pros are left-handed.
  • In baseball, lefty batters are a step closer to first base.
  • Fencers also have an advantage.

On the not so good side, left-handed people are three times more likely than right-handed people to become alcoholics, presumably due to the right side of the brain having a lower tolerance for alcohol than the left side. Left-handers usually reach puberty 4 to 5 months after right-handers

As you know by now, I'm left handed. My 3-year-old grandson (who inspired this essay) also appears to be left-handed. So is his other grandfather!

I am very happy to be in the computer age so my handwriting ability is not as critical as it was in the past. Even so, keyboards (and pianos) have a right hand prejudice with most of the action on the right side. Computer “mice” are generally right sided, as are both the auto and bike shift controls. Tools and sports equipment are generally designed for the right handed. And I still think about where to sit in a classroom or at a crowded dining table.

With it all, lefties have a nice place today in our creative world. We're seldom “left” out or “left” behind.

And “left” to our own devices, we help keep everyone else balanced!

Past Health Advice Articles

Dr. Allen Weiss is CEO & President of the NCH Healthcare System. He is board certified in Internal Medicine, Rheumatology and Geriatrics, and was in private practice in Naples, Florida from 1977 - 2000. Dr. Weiss is active in a variety of professional organizations and boards, and has been published in numerous medical journals, including the American Journal of Medicine and the Journal of Clinical Investigation.