As handedness is a highly heritable trait associated with various medical conditions, and because many of these conditions could have presented a Darwinian fitness challenge in ancestral populations, this indicates left-handedness may have previously been rarer than it currently is, due to natural selection.
But other research suggests that there are probably dozens of genes that play a role in determining whether we end up writing with our left hand or our right. On top of that, other studies have linked factors such as oestrogen levels and birth position to varying levels of left- and right-handedness.
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.
Special or not, lefties are born, not made: Genetics are at least partially responsible for handedness. Up until last year, it was assumed that hand preference comes from asymmetrical genes in the brain—two hands, two brain hemispheres, one is dominant.
If two parents are right-handed, their offspring has a 10% chance of being left-handed. However, if one or both parents are left-handed, the chance of their child being left-handed becomes higher at 18 to 22% and 27%, respectively.
Sex – slightly more boys than girls are left-handed. This suggests to some researchers that the male hormone testosterone has an influence on right and left-handedness. Fetal development – some researchers believe that handedness has more of an environmental influence than genetic.
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.
This is often associated with enhanced intuition, emotion, imagination and creativity. Left-handed people are also believed to be better at thinking outside the box and problem-solving, which could be a big advantage as your child approaches school age.
If both parents are left handed, about 25% of the time the child will be left handed. If none are, it's about 10%. Other factors contribute as well, it's a complex trait. But based purely on the baseline, no left handed parents, about 1/10*10 times, or 1/100 times you'll get two consecutive lefties.
Overall, individuals with ADHD had a 27.3 percent chance of being either left-handed or mixed-handed compared to 18.1 percent in the general population. So the results suggest that the effects are smaller than for the autism spectrum, but generally go in the same direction.
Being left-handed is the result of genes and environment. About 50 per cent more males than females are left-handed and 17 per cent of twins are, compared with about 10 per cent in general. The 'vanishing twin' hypothesis suggests that left-handers were originally a twin, but the right-handed foetus failed to develop.
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.
For example, left handedness determined by grip strength has been shown to be associated with poorer cognitive function [12], whereas left handedness, via self-report, has been shown to be associated with better memory and attention task performance [13].
Sometimes people who are left-handed are called many different things, “Southpaws”, "Lefties", and other simply mean names, like "Weird" or "Strange".
Handwriting is considered the most challenging daily activity for left-handed children to perform, I can confirm. My baseline orientation (writing on the line) and spatial awareness was a struggle in grade school.
Researchers have not yet found a genetic link between dyslexia and handedness and individuals with dyslexia, a learning difficulty that affects reading, writing and spelling abilities, are split 50:50 between right and left-handedness. However, there are fewer left-handed people in the world.
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.
Australia sits with about 10 per cent of the population. In many parts of the world there's still some bias against left-handers – the left hand can be considered dirty (it's usually the one that gets the job of ah, wiping, whereas the right hand is for eating, shaking hands, that sort of thing).
Lefties make up only about 10 percent of the population, but studies find that individuals who are left-handed score higher when it comes to creativity, imagination, daydreaming and intuition. They're also better at rhythm and visualization.
Browse through a list of history's most famous left-handers and you are likely to see Albert Einstein's name. You may even see people tying Einstein's genius to his left-handedness.
Our confidence intervals at a 95% confidence level show that the average IQ for a left handed person is between 117.73 and 127.19 and for a right handed person it is between 109.9 and 123.5.
Some children experience them from early stages of literacy education, while others occur at a later stage while reading texts. In comparison to right-handed people, left-handed people are 2.5-3 times more likely to have difficulty in mastering written speech -- in both writing and reading.