Cure Brain health
Myths And Interesting Facts About Being Left-Handed
CureJoy Editorial Feb 7, 2018
Facts And Myths About Lefties
Facts: 10% Of Population Is Left Handed, First Seen In Mother's Womb, Listens Differently
Myths: Lefties Are Mentally Unstable, Creative, Identical Twins Have Identical Handedness
Left-handedness can be seen as early as when a baby is in its mother's womb. But can your dominant hand really determine your health, well-being, and creativity? Does being a leftie or "south paw" really make you special? Discover some fun facts about being left-handed, like whether identical twins have the same handedness and if lefties are more creative yet have a higher risk for health issues.
The internet is rife with "facts" about what makes left-handed people so special. But how much of this is myth? According to The Handedness Research Institute, research on the subject can vary quite a bit due to the multiple theories surrounding what actually determines handedness.1 However, there are some things that seem rather certain. Here's a closer look at the reality behind being left-handed.
What Causes Left-Handedness?
As you'd probably guess, left-handedness involves a consistent use of, higher skill with, and preference for the left hand over the right.2 The vast majority of the population is right-handed, which is why scientists and researchers have been fascinated to find out what makes some people left-hand dominant. They've recognized a few different possibilities, including gender (men have more chances of being lefties), genes, family history, the mother's handedness, and age of the mother (as well as high testosterone levels in the mother) when the baby is conceived.3
Fun Facts About Left-Handed People
1. About 10 Percent Of The Population Is Left-Handed
Not everyone who has a tendency to be left-handed stays that way. Cultural norms often nudge people toward being right-handed. Some traditional cultures even saw left-handedness as being deviant or unsuitable. Fortunately, these ideas have changed over time, and in Western cultures today, about 10 to 15 percent of the population is left-handed.4
2. Left-Handedness First Shows Up In The Womb
Left-handedness can be seen as early as when a baby is in its mother's womb! One study found that 85 percent of fetuses demonstrated preference for the right arm over the left already at 10 weeks of gestation. This suggests that this laterality is controlled by muscle or the spine rather than the brain as previously proposed. The researchers believe that this early motor behavior may actually go on to influence the handedness or asymmetry of the growth of the brain.5
3. Left-Handedness May Increase The Risk Of ADHD And Dyslexia
Research has uncovered a link between handedness and increased risk for certain illnesses. One study found that mixed-handedness puts a person at greater risk of developing ADHD or attention-deficit/hyperactivity disorder, dyslexia, and language-related learning difficulties. Unlike right-handed people who have one dominant hemisphere, many left-handed people have no dominant hemisphere at all – and this is what could pose a problem.6
4. Lefties Listen Differently
Being left-handed may even change how you hear the world around you! Researchers say that the left hemisphere of the brain is where language is primarily processed and rapidly changing sounds are analyzed. In one study, subjects were asked to hit a button when they heard background sounds. Researchers found that results varied depending on which hand was used to press the button. When the right hand was used, the left hemisphere was controlling it and vice versa. The sounds heard were different depending on the hand pressing the button. The right hemisphere responded to syllables and intonation (slow-changing sounds), while the left hemisphere seemed to "like" more rapidly changing ones like consonants. Motor systems could, therefore, influence what you hear.7
5. The Absence Of "Right Shift" Bias Influences Left-Handedness
One theory suggests that genes may not actually determine whether you become left-handed, but they can influence whether you express a right-handed bias. In the absence of a right shift bias, you may end up becoming left-handed or right-handed. This is a subtle but critical difference that explains why your genes and parents' left-handedness may play a role in the odds that you end up a leftie too. But it can also explain why everyone in that family doesn't end up left-handed.8 Backing this up, one study found that two left-handed parents had 30 to 40 percent left-handed offspring, while two right-handed parents were far less likely to have any kids who were lefties.9
5 Left-Handedness Myths Busted!
People have come up with a whole bunch of wild ideas about lefties – many of which aren't backed by scientific research or proof. Here are a few of those myths:
1. Lefties Are Dangerous Or Mentally Unstable
Left-handedness was once considered ungodly or sinister in some way. But we now know better. Studies that show a link between left-handedness and psychotic disorders have been misinterpreted. One study of 107 patients at an outpatient psychiatric clinic revealed that about 40 percent of those who had a schizoaffective disorder or schizophrenia were left-handed. While this research found that those with psychotic disorders do have a higher ratio of left-handedness than the normal population, it doesn't mean that every left-handed person has a psychotic disorder! In fact, mood disorders like bipolar disorder and depression reflect the same percentage of lefties as that of the general population (about 11 percent).10
2. Being Left-Handed Means You're Creative
Research has shown that left-handed people's brains are actually wired slightly differently. Studies comparing the creativity of left-handed subjects to right-handed subjects found that the southpaws demonstrated greater creativity in the test administered.11 However, this is not a guaranteed or universal phenomenon. What is more common in lefties is divergent thinking, which is considered a key ingredient for creativity. Creative innovation relies on the right hemisphere of the brain, while creative output (motor/verbal output) on the left. Divergent thinking, however, requires a full cooperation between both hemispheres for the creative process overall. Lefties with a larger corpus callosum, the portion of the brain that handles communication between both hemispheres and which enables divergent thinking, may be predisposed to be more creative.12 In short, this may improve your chances of being creative if you're a leftie, but it's certainly no guarantee.
3. Identical Twins Must Have Identical Handedness
Even monozygotic twins, the most identical of all human beings on the planet, can be different when it comes to handedness. As one study found, 23 percent of identical twins with the same set of genes did not share the same handedness.13
4. Genes Determine Left- or Right-Handedness
Your genes alone don't determine your dominant hand – but they do play a small role. For a long while, we believed that the genetic activity in the brain determines whether you are left-handed or right-handed. 14 In fact, one group of researchers believe they have isolated the actual gene responsible for handedness (LRRTM1).15 But this doesn't take into account why the identical twins in the aforementioned study don't have the same handedness in 100 percent of pairs.16
5. You Can't Change Handedness
A closer look at the statistics on left-handedness shows that overcoming handedness may be possible. Just over a century ago, just 2 percent of the population were left-handed. Compare that to today's 10 percent average. It's unlikely that percentage has really changed, but social norms have allowed more people to stick with their natural leaning.17
While it may not be socially unacceptable to be a leftie anymore, there are still some who feel or are pressured to conform to the larger population's right-handedness. As one piece of research revealed, as many as 11 percent of the 650 young adults contacted had attempted to try and change their hand preference from left to right. In addition, 8 percent confessed to feeling pressured to switch to being right-handed. Of this group, some had succeeded in switching to using their right hand. Researchers say that women may be more successful at changing their handedness; however, this needs to be backed up with more research.18
1. ↑ Research. Handedness Research Institute
2, 4, 14, 17. ↑ Medland, Sarah E., David L. Duffy, Margaret J. Wright, Gina M. Geffen, David A. Hay, Florence Levy, Catherina EM Van-Beijsterveldt et al. "Genetic influences on handedness: data from 25,732 Australian and Dutch twin families." Neuropsychologia 47, no. 2 (2009): 330-337.
3. ↑ Szaflarski, Jerzy P., Jeffrey R. Binder, Edward T. Possing, Kristen A. McKiernan, B. Douglas Ward, and Thomas A. Hammeke. "Language lateralization in left-handed and ambidextrous people fMRI data." Neurology 59, no. 2 (2002): 238-244.
5. ↑ Hepper, Peter G., Glenda R. Mccartney, and E. Alyson Shannon. "Lateralised behaviour in first trimester human foetuses." Neuropsychologia 36, no. 6 (1998): 531-534.
6. ↑ Rodriguez, Alina, Marika Kaakinen, Irma Moilanen, Anja Taanila, James J. McGough, Sandra Loo, and Marjo-Riitta Järvelin. "Mixed-handedness is linked to mental health problems in children and adolescents." Pediatrics 125, no. 2 (2010): e340-e348.
7. ↑ New Study: How People Move Affects Their Hearing. Georgetown University.
8. ↑ Annett, Marian. Handedness and brain asymmetry: The right shift theory. Psychology Press, 2002.
9. ↑ Llaurens, Violaine, Michel Raymond, and Charlotte Faurie. "Why are some people left-handed? An evolutionary perspective." Philosophical Transactions of the Royal Society B: Biological Sciences 364, no. 1519 (2009): 881-894.
10. ↑ Webb, Jadon R., Mary I. Schroeder, Christopher Chee, Deanna Dial, Rebecca Hana, Hussam Jefee, Jacob Mays, and Patrick Molitor. "Left-handedness among a community sample of psychiatric outpatients suffering from mood and psychotic disorders." SAGE Open 3, no. 4 (2013): 2158244013503166.
11. ↑ Newland, G. Anthony. "Differences between left- and right-handers on a measure of creativity." Perceptual and Motor Skills 53, no. 3 (1981): 787-792.
12. ↑ Moore, Dana W., Rafeeque A. Bhadelia, Rebecca L. Billings, Carl Fulwiler, Kenneth M. Heilman, Kenneth MJ Rood, and David A. Gansler. "Hemispheric connectivity and the visual–spatial divergent-thinking component of creativity." Brain and cognition 70, no. 3 (2009): 267-272.
13, 16. ↑ Corballis, Michael C. "Left brain, right brain: facts and fantasies." PLoS Biol 12, no. 1 (2014): e1001767.
15. ↑ Francks, Clyde, Shinji Maegawa, Juha Laurén, Brett S. Abrahams, Antonio Velayos-Baeza, Sarah E. Medland, Stefano Colella et al. "LRRTM1 on chromosome 2p12 is a maternally suppressed gene that is associated paternally with handedness and schizophrenia." Molecular psychiatry 12, no. 12 (2007): 1129-1139.
18. ↑ Porac, Clare, Stanley Coren, and Alan Searleman. "Environmental factors in hand preference formation: Evidence from attempts to switch the preferred hand." Behavior genetics 16, no. 2 (1986): 251-261.
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