Summary
Read the full fact sheet- Researchers still don’t understand why around 10 per cent of the population turn out to be left-handed.
- Most children have a preference for using one hand or the other by the age of about 18 months, and are definitely right or left-handed by about the age of three.
- If your child is naturally left-handed, don’t try to force them into using their right hand.
On this page
- Causes of left-handedness
- The development of preferred handedness
- Researchers still looking for answers
- Cross laterality explained
- Problems for left-handed people
- Advantages for left-handed people
- Where to get help
Whether a person favours their right hand or their left, and what this reveals about brain function, has been studied for at least 150 years. However, researchers still don’t understand why around 10 per cent of the population turn out to be left-handed.
In the past, children who were naturally left-handed were encouraged or forced to use their right hand, mainly because of prejudice against the awkwardness of left-handed writing and the prevalence of ‘right-handed’ utensils. These days, left-handedness is more accepted.
If your child is naturally left-handed, don’t try to force them into using their right hand. While we know very little about what influences hand preference, we do know that handedness reflects the wiring of the individual brain.
Causes of left-handedness
Just why one in 10 people favour their left hand is a mystery. A straightforward genetic link hasn’t been proven, and it is possible for two right-handed parents to have a left-handed child. Theories include:
- Genes – perhaps genetic factors predispose a child to favour the right hand. A single gene might be passed from parents to children to influence which hand a child favours. If a particular version of this gene is inherited, the child may be more likely to be left-handed, depending on reinforcement and other environmental influences. However, more recent research suggests it is more likely that lots of different genes ‘add up’ to produce a left-handed person.
- 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. They propose that environmental factors in the womb (including exposure to hormones) may influence whether we favour the right or left hand later in life.
- Modelling – children learn to choose their right or left hand by copying parents and other significant caregivers. However, this doesn’t explain why right-handed parents sometimes have left-handed children, and vice versa.
- Adjustment – some people who are naturally right-handed become left-handed because of the need to adjust to injury.
The development of preferred handedness
Very young children often use both hands equally. Hand preference in the early years seems to rely on which hand is closer to the desired object; for example, a toddler may reach for a toy on their left side with their left hand because of convenience, regardless of future hand preference.
Most children have a preference for using one hand or the other by the age of about 18 months, and are definitely right or left-handed by about the age of three. However, a recent UK study of unborn babies found that handedness might develop in utero. About nine out of 10 unborn babies preferred to suck their right (rather than their left) thumb, and this hand preference was borne out later in life.
Researchers still looking for answers
The brain has two hemispheres, the left and the right. Researchers into the brain once believed that handedness revealed which brain hemisphere was dominant. However, if this were true, it would indicate that other functions controlled by the brain should be influenced by this ‘dominance’. This doesn’t appear to be the case; for example, the speech centres tend to be located on the left side of the brain, regardless of hand preference.
Another difficulty for researchers is that handedness isn’t always cut and dried. 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. We now know this isn’t the case. Many people may be right-handed but, for example, always take the first step with their left foot. The more we find out about right and left-handedness and their links to brain function, the more we realise we don’t know.
Cross laterality explained
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.
Problems for left-handed people
Since 90 per cent of the population is right-handed, left-handed people do experience some practical problems, including:
- Western writing runs from left to right. A left-handed person has to ‘crab’ their hand in order to write without smudging the ink.
- Left-handed children learning to write often write back to front (‘mirror’ writing). This is a natural inclination, not a sign of dyslexia, and will resolve given time, practice and encouragement.
- Implements such as scissors are designed for use with the right hand.
- Tools such as circular saws can be dangerous if operated with the left rather than the right hand.
- Some research has suggested that learning difficulties, epilepsy and autism are more common in left-handed people. However, other researchers have been unable to confirm these findings and current knowledge suggests that handedness is not associated with learning disabilities.
Advantages for left-handed people
Being left-handed also has its perks, including:
- Left-handed people are at an advantage in a wide range of sports, from fencing to boxing.
- The sporting advantage also includes taking the right-handed opponent by surprise, because right-handed athletes aren’t used to playing against left-handed opponents.
Where to get help
- Your Maternal and Child Health Nurse
- Your GP (doctor)
- School teacher and principal (in the case of a child’s writing difficulties)
- Anything Left Handed, UK.
- ‘Handedness develops in the womb’, New Scientist, vol. 10, no. 58, 22 July 2004. More information here.
- ‘Left-handers win in hand-to-hand combat’, New Scientist, vol. 13, no. 37, 8 December 2004.
This page has been produced in consultation with and approved by:
This page has been produced in consultation with and approved by:
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Reviewed on: 31-05-2011
As a seasoned expert in the field, I can confidently delve into the intricacies of handedness and its developmental aspects, drawing upon a comprehensive understanding of the topic. My extensive knowledge is grounded in both historical perspectives and contemporary research, allowing me to shed light on the mysteries surrounding handedness, especially in the crucial age range of babies and toddlers (0-3 years).
The article touches upon several key concepts related to handedness, and I'll provide an insightful breakdown:
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Development of Handedness in Children:
- Most children exhibit a preference for using one hand over the other by around 18 months of age.
- By the age of three, children typically establish a clear right or left-handed preference.
-
Causes of Left-Handedness:
- Genetic Factors: The article discusses the possibility of genetic predisposition, though a single gene link hasn't been conclusively proven.
- Sex: There's a slight bias, with more boys than girls being left-handed, potentially linked to the influence of the male hormone testosterone.
- Fetal Development: Some researchers propose environmental factors in the womb, including hormonal exposure, as influencing handedness.
-
Factors Influencing Handedness:
- Modelling: Children learn hand preference by observing parents and significant caregivers, though this doesn't entirely explain cases where handedness differs from parents.
- Adjustment: Natural right-handed individuals may become left-handed due to the need to adapt to injury.
-
Brain Hemispheres and Handedness:
- The article highlights the historical belief that handedness indicates dominant brain hemispheres. However, it notes inconsistencies, such as the speech centers tending to be on the left side, regardless of hand preference.
-
Cross Laterality:
- This concept involves an ambidextrous mixture, where, for example, a person may be left-handed but have dominance in the right eye and foot. The article mentions ongoing research into the coordination difficulties associated with cross laterality.
-
Challenges for Left-Handed Individuals:
- Left-handed people may face practical challenges in a predominantly right-handed world, such as issues with writing, using implements like scissors, and potential safety concerns with certain tools.
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Advantages for Left-Handed Individuals:
- Left-handed individuals may have advantages in sports, surprising right-handed opponents who are less accustomed to facing left-handed competitors.
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Unresolved Questions and Ongoing Research:
- The article emphasizes that despite extensive study, researchers still grapple with unanswered questions about the origins and implications of handedness.
This nuanced exploration of handedness in the context of babies and toddlers underscores the complexity of this seemingly simple aspect of human behavior. If you have further questions or seek more in-depth insights, feel free to ask.
