Bias against people who are left-handed includes handwriting, which is one of the biggest sources of disadvantage for left-handed people, other than for those required to work with certain machinery. About 90 percent of the world's population is right-handed, and many common articles are designed for efficient use by right-handed people, and may be inconvenient, painful, or even dangerous for left-handed people to use. These may include school desks, kitchen implements, and tools ranging from simple scissors to hazardous machinery such as power saws.
Beyond being inherently disadvantaged by a right-handed bias in the design of tools, left-handed people have been subjected to deliberate discrimination and discouragement. In certain societies, they may be considered unlucky or even malicious by the right-handed majority. Many languages still contain references to left-handedness to convey awkwardness, dishonesty, stupidity, or other undesirable qualities. In many societies, left-handed people have been historically forced as children to use their right hands for tasks which they would naturally perform with the left, such as eating or writing.
Favorable perceptions
In Tibetan tantric Buddhism, the left hand represents wisdom.
In early Roman times, the left side retained a positive connotation, as the Augures proceeded from the eastern side.
Unfavorable perceptions The unfavorable associations and connotations of the use of the left hand among cultures are varied. In some areas, in order to preserve cleanliness where sanitation was an issue, the right hand, as the dominant hand of most individuals, was/is used for eating, handling food, and social interactions. The left hand would then be used for personal hygiene, specifically after urination and defecation. Personal hygiene rules in Islam prefer this, as derived from hadith sources. These rules were imposed on all, no matter their dominant hand. Through these practices, the left hand became known as the "unclean" hand. Currently, amongst Muslims and in some societies including Nepal and India it is still customary to use the left hand for cleaning oneself with water after defecating. The right hand is commonly known in contradistinction from the left, as the hand used for eating.
In many religions, including Christianity, the right hand of God is the favored hand. For example, Jesus sits at God's right side. God's left hand, however, is the hand of judgement. The Archangel Gabriel is sometimes called "God's left hand" and sits at God's left side. Those who fall from favor with God are sent to the left, as described in Matthew 25: 32–33, in which sheep represent the righteous and goats represent the fallen: "And he shall separate them one from another, as a shepherd divideth his sheep from the goats. And he shall set the sheep on his right, but the goats on his left." In 19th-century Europe, homosexuals were referred to as "left-handed". In Protestant-majority parts of the United Kingdom, Catholics were called "left-footers", and vice versa in Catholic-majority parts of Ireland and Irish America. ;
Various innocuous activities and experiences become rude or even signs of bad luck when the left hand becomes involved. In some parts of Scotland, it is considered bad luck to meet a left-handed person at the start of a journey. In Ghana, pointing, gesturing, giving or receiving items with the left hand is considered taboo or rude. A person giving directions will put their left hand behind them and even physically strain to point with their right hand if necessary.
Forced use of the right hand Owing to cultural and social pressures, many left-handed children were forced to write and perform other activities with their right hands. This conversion can cause multiple problems in the developing left-handed child, including learning disorders, dyslexia, stuttering and other speech disorders. Shifts from left- to right-handed are more likely to be successful than right to left, although neither have a high success rate. Successful shifters are more likely to become ambidextrous than unsuccessful ones. Conversions can be successful with consistent daily practice in a variety of manual activities, but even if activity in the non-dominant left-hemisphere of the brain will increase during tasks, so too will activity in the dominant right-hemisphere. Consistent left-handers have no higher activity in these task centers than converted left-handers, so it may be inferred that "attempts to switch handedness by educational training far from weakening the functional expression of lefthandedness in higher-order motor areas of the (dominant) right hemisphere in fact enhance it".
Many Asian countries force their children to become right-handed due to cultural perceptions of bad luck associated with the left hand. In India, Pakistan, Bangladesh and Indonesia, it has traditionally been perceived as "rude" behaviour to use the left hand for eating, as the left hand is commonly used for tasks considered "unclean". In a 2007 study in Taiwan, about 59.3% of naturally left-handed children studied had been forced to convert to right-handedness. The study took into account economic status of the children's families and found that children whose parents had less education were more likely to be forced to convert. Even among children whose parents had higher levels of education, the conversion rate was 45.7%. The proportion of females in Japan subjected to forced conversion is significantly higher compared to males (95.1% to 81.0%).
Malawians state their views that "the left hand is less skilled and less powerful than the right one" as main reasons for forcing left-handers to convert. Among students, teachers and parents, 75% said the left hand should not be used to perform habitual activities, and 87.6% of these believed left-handers should be forced to switch dominant hands. Parents and close relatives are most responsible for impressing these beliefs upon their children.
In the Soviet Union, all left-handed students were forced to write with their right hand, as is the case with Vietnam.А. П. Чуприков, В. Д. Мишиев. // Латеральность населения СССР в конце 70-х и начале 80-х годов. К истории латеральной нейропсихологии и нейропсихиатрии. Хрестоматия. Донецк, 2010, 192 с.А. П. Чуприков, Е. А. Волков. // Мир леворуких. Киев. 2008.
George VI (1895–1952, British King from 1936) was naturally left-handed as a child. He was forced to write with his right hand, as was common practice at the time, but was not expected to become king, so that was not a factor.
Growing acceptance of left-handedness (late 20th century) On March 8, 1971, The Florence Times—Tri-Cities Daily reported that left-handed people "are becoming increasingly accepted and enabled to find their right (or left) place in the world". The Florence Times—Tri-Cities Daily also wrote, "we still have a long way to go before the last vestiges of discrimination against left-handedness are uprooted, however." The frequency of left-handed writing in the United States, which was only 2.1 percent in 1932, had risen to over 11 percent by 1972. According to an article by The Washington Post from August 13, 1979, a University of Chicago psychologist, Jerre Levy, said, "In 1939, 2 percent of the population wrote with the left hand. By 1946, it was up to 7 1/2 percent. In 1968, 9 percent. By 1972, 12 percent. It's leveling off, and I expect the real number of left-handers will turn out to be about 14 percent." According to the article by The Washington Post from August 13, 1979, "a University of Michigan study points out that left-handers may not be taking over the world but ... 7 percent of the men and 6 percent of the women over 40 who were interviewed were lefties, but the percentages jumped to well above 10 percent in the 18-to-39 age group." According to the article by The Washington Post of August 13, 1979, Dr. Bernard McKenna of the National Education Association said, "There was recognition by medical authorities that left-handedness was normal and that tying the hand up in a child often caused stuttering." In Japan, Tokyo psychiatrist Soichi Hakozaki coped with such deep-seated discrimination against left-handed people that he wrote The World of Left-Handers. Hakozaki reported finding situations in which women were afraid their husbands would divorce them for being left-handed. According to the aforementioned article, an official at the Japanese Embassy said that, before the war, there was discrimination against left-handers. "Children were not trained to use their left hand while eating or writing. I used to throw a baseball left-handed, but my grandparents wanted me to throw right-handed. I can throw either way. Today, in some local areas, discrimination may still remain, but on the whole, it seems to be over. There are many left-handers in Japan." In a further article in The Washington Post of December 11, 1988, Richard M. Restak wrote that left-handedness has become more accepted and people have decided to leave southpaws alone and to stop working against left-handedness. In an article by The Gadsden Times from October 3, 1993, the newspaper mentioned a five-year-old named Daniel, writing, "the advantage that little Daniel does have of going to school in the '90s is that he will be allowed to be left-hander. That wasn't always the case in years past." In a 1998 survey, 24 percent of younger-generation left-handed people reported some attempts to switch their handedness.
In 1999, Swiss researchers took 1,700 Swiss adults ages 34–74 and divided them into age groups, with the youngest being 35–44 and the oldest being 65–74. The researchers found almost twice as many people in the youngest age group considered themselves left-handed when compared to the oldest age group. In addition, the incidence of the older group switching to their right hand for writing was more than triple that of the younger group. Researchers found that among the four age groups and the prevalence of left-handedness declined from 11.9% among 35 to 44 year olds and roughly 12.5% among 45 to 54 year olds to roughly 8% among 55 to 64 year olds and 6.2% among 65 to 74 year olds. Additionally, researchers found that only 26.6% of 35 to 44 year olds switched to right-handedness for writing and roughly 73% wrote with their left hand. Among 45 to 54 year olds, roughly 52% write with their right hand and roughly 48% write with their left hand. Roughly 85% of 55 to 64 year olds wrote with their right hand and roughly 15% of 55 to 64 year olds wrote with their left hand. 88.9% of 65 to 74 year olds wrote with their right hand while 11.1% wrote with their left hand.B Galobardes, M S Bernstein, and A MorabiaDivision of Clinical Epidemiology, University Hospital of Geneva, Switzerland. [email protected] "The association between switching hand preference and the declining prevalence of left-handedness with age.", American Journal of Public Health 89, no. 12 (December 1, 1999): pp. 1873-1875.
In the early 1990s, there was controversy among researchers over whether left-handed people die earlier or whether it is due or not due to fewer left-handed people among the elderly. The debate was controversial and researchers argued that left-handedness was less common among the elderly because some left-handed people might die in accidents or injuries due to using objects made for right-handed people. Researchers also argued that left-handed people were less common among elderly people because people in the earlier 20th century often were forced to become right-handed, a practice that disappeared in the late 20th century.