Researchers into the brain once believed that handedness revealed which brain hemisphere was dominant. While some people use one hand exclusively for all tasks, others tend to swap depending on the activity; for example, some people write with their left hand but open jars with their right.
It was once believed that a right-handed person has general dominance on the right side of their body, which means their favoured foot, eye and ear are also on their right side. Many people may be right-handed but, for example, always take the first step with their left foot. Cross laterality is an ambidextrous mixture for example, being left handed but dominant in the right eye and foot. This may cause coordination difficulties.
However, some sports such as gymnastics benefit from the distribution of brain dominance. Research into cross laterality is ongoing. Since 90 per cent of the population is right-handed, left-handed people do experience some practical problems, including:.
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People who run regularly seem to be susceptible to Achilles tendonitis. Acromegaly is caused by an excess of growth hormone in adults, which causes the overgrowth of bones in the face, hands, feet and internal organs. Exercise can prevent age-related changes to muscles, bones and joints and can reverse these changes too. A person with amyloidosis produces aggregates of insoluble protein that cannot be eliminated from the body.
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Recent research suggests that children who are strongly left or right handed also have good cerebral lateralisation and typical language production. On the other hand, mixed-handedness not developing a dominant hand has been linked with atypical development of motor and language abilities.
Children with ASDs also show motor abnormalities as early as seven months of age. Current diagnoses of ASDs tend to occur relatively late, when children fail to produce and understand basic language.
Late diagnoses can limit benefits that may come from early interventions and therapies. Infant brains are incredibly flexible and the right kinds of early intervention may improve later cognitive development and mental health.
Handedness is not the only bias of our motor skills that comes from cerebral lateralisation. A majority of the population has a right hemisphere of the brain that is dominant for responding to danger. This means that we are faster at recognising threatening faces and expressions when they appear to our left side in the left visual field compared to our right side. This has been demonstrated in a range of classic psychology laboratory studies where adults are faster to judge pictures of faces expressing negative emotions presented to their left compared to those presented to their right.
Mapping the developmental paths of motor biases and cognitive abilities in children provides a novel way for us to better understand the relationship between brain organisation, brain function and behaviour. Portsmouth Climate Festival — Portsmouth, Portsmouth. Handedness, or hand preference, is the tendency to be more skilled and comfortable using one hand instead of the other for tasks such as writing and throwing a ball. Although the percentage varies by culture, in Western countries 85 to 90 percent of people are right-handed and 10 to 15 percent of people are left-handed.
Mixed-handedness preferring different hands for different tasks and ambidextrousness the ability to perform tasks equally well with either hand are uncommon. Hand preference begins to develop before birth.
It becomes increasingly apparent in early childhood and tends to be consistent throughout life. However, little is known about its biological basis. 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. The right hemisphere controls movement on the left side of the body, while the left hemisphere controls movement on the right side of the body. It was initially thought that a single gene controlled handedness. However, more recent studies suggest that multiple genes, perhaps up to 40, contribute to this trait. Each of these genes likely has a weak effect by itself, but together they play a significant role in establishing hand preference.
Studies suggest that at least some of these genes help determine the overall right-left asymmetry of the body starting in the earliest stages of development. So far, researchers have identified only a few of the many genes thought to influence handedness. For example, the PCSK6 gene has been associated with an increased likelihood of being right-handed in people with the psychiatric disorder schizophrenia.
Another gene, LRRTM1 , has been associated with an increased chance of being left-handed in people with dyslexia a condition that causes difficulty with reading and spelling. It is unclear whether either of these genes is related to handedness in people without these conditions. Studies suggest that other factors also contribute to handedness.
The prenatal environment and cultural influences may play a role.
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