For many people, being left-handed means there are a lot of little, everyday inconveniences that you just learn to deal with; from scissors to desks, the world was designed for right-handed people. But there are some very weird things that go along with being left-handed, including a long history of suspicion and distrust, along with a scientifically proven tendency to develop a mental illness.
10.People With Psychotic Disorders Are More Likely To Be Left-Handed
Left-handed people have long been viewed with a certain amount of suspicion. Recently, science has shown that there might be a solid reason for that. In 2013, Yale University researcher Jadon Webb conducted a survey among patients diagnosed with different types of psychotic illnesses, including schizophrenia. Participants in the study were asked to fill out a questionnaire, which included the question about which hand they wrote with. The results were surprising. Researchers found that about 40 percent of those who were suffering from psychosis were left-handed. That's a significant percentage, considering that only about 10 percent of the population is left-handed.
Researchers believe that being left-handed involves having a sort of biomarker that might indicate a predilection toward mental illness—specifically psychosis. In studies done with other groups suffering from mental illness such as depression, there was no similar correlation. When these other groups were studied, there was a much more expected pattern where the number of left-handed sufferers was comparable to the overall percentage of left-handed people in the population.
9.Our Ancestors Also Had A Left-Handed Minority
We tend to think of right- or left-handed dominance in terms of modern things, like what hand we write with or use for the television remote. But, it turns out, early humans were favoring one or the other even 500,000 years ago. Researchers have taken a look at Neanderthal tools and have found that the vast majority of them show wear and tear consistent with right-handed use. Many of the tools were used in the cleaning of hides, which the individual would typically grip with their teeth and rake with a tool to clean. Teeth would often get scratched by the stone tool, and the direction of the scratches indicates which hand was used. In most cases, it was the right hand. There were, of course, left-handed individuals. Today, about 10 percent of the population is left-handed, which seems to be fully consistent with the researchers' findings about Neanderthals. This supports the theory that they're much more like us than has been previously thought. Even other animals that are thought to be pretty close to us on the evolutionary tree—like gorillas and chimpanzees—are only about 5 percent more likely to favor their right hands than their left hands.
8.Left-Handed Tendencies And Language
No other animal has such a huge bias against being left-handed. So why humans? It's thought that it has something to do with language. For most people, language develops in the left side of the brain—specifically, in Broca's area. This is where we not only develop ideas but translate them into a form of communication that others can understand. Since the left side of the brain controls the right side of the body, the prevalence of right-handed individuals is an outward sign of left-brain dominance.
However, it's now been discovered that, in some people, language skills happen in the right side of the brain. These individuals are subsequently left-handed. It's not just that cut-and-dried, either. The more a person favored one hand or the other, the stronger the connection was with the other side of the brain. People who use their left hand for almost everything have an extremely high chance of being right-brain language dominant. Additionally, those who have a familial history of a high rate of left-handed individuals also have a stronger right-brain language processing center, suggesting that as a species we became left-handed and right-handed when we started developing language.
7.Left-Handed Spiral Stairs
It's well known that many medieval castles have spiral staircases built as a defense measure. A spiral staircase that turns clockwise gives the defender (presumably the one backing up the stairs or coming down them) a better freedom of movement. The defender can place his left hand on the central "post" for balance and strike down with the sword in his right hand. That assumes the defenders are right-handed, which is a problem for those who aren't. So what's a left-handed lord to do?
Ferniehirst Castle in Scotland is the ancestral home of the Kerr family, which traces their family tree back to their arrival in Britain alongside William the Conqueror in 1066. They're said to have a long history of left-handedness running in the family. According to the story, many of the Kerr homes and castles—like Ferniehirst—were constructed with spiral staircases that go counterclockwise (as pictured above) instead of the traditional clockwise ones. This allowed the largely left-handed clan to maximize their defenses, making it easier for them to fight while simultaneously presenting a major challenge to anyone who tried to take their castles by force. The early lords discovered the massive advantage held by left-handed fighters, and it became tradition to train all their guards and soldiers to fight left-handed. This lead to the term "Kerr-handed" or "corrie-fisted" to describe someone who favors their left hand.
苏格兰的芬尼赫斯特城堡（ Ferniehirst Castle）是科尔（Kerr）家族祖传的居所。科尔家族的先祖随着威廉一世（William the Conqueror）在1066年来到英国。左撇子在这个家族的传承中由来已久。因此，科尔名下的房屋、城堡——比如芬尼赫斯特城堡——都采用了逆时针的左旋阶梯（如上图所示）而非传统的顺时针。大部分科尔宗族借此增强了他们的防御力，使得他们在战斗的同时更好地阻止入侵者。那些公爵们发现这些左撇子士兵在对战中占有很大的优势，因此他们开始特意训练他们的警卫和士兵们左手持剑。久而久之，左撇子就又被大家称为"科尔军队"（Kerr-handed）或者"苏格兰拳头"（corrie-fisted）。
6.Fear Of The Left-Handed Might Be Innate
History hasn't been kind to the left-handed. They were made to retrain their hands and even punished for using the "wrong" one. But now, science is suggesting that it's not just the desire to make people conform to a certain standard that has created this bias against left-handed people. According to researchers at the University of Utah, things that have to do with our left side are innately more scary. For the experiment, researchers exposed their subjects to a number of different threats, coming from either their right or left side. For example, in one case, participants were told that an earthquake had hit to the left or to the right of their city (on a map shown) and asked whether they would evacuate because of the danger of aftershocks. The earthquake to their left was seen as much scarier, and more people chose to evacuate.
Similar results were found when the threat was changed to a radioactive disaster; even though the occurrence on the right was closer, the left was viewed as more of a threat. People were also more disgusted by objects on their left, as illustrated by how far out of their way they went to avoid things like fake poop. There are a couple of different theories about why this happens, such as our brain's tendency to overcompensate for things and favor the right, as well as most of us feeling more capable of defending ourselves from threats on our stronger—right—side.