|Movement Experiences for Children|
|Instructor:||Dr. Shannon S.D. Bredin|
|Important Course Pages|
Handedness is a characteristic that is common amongst most adults, where one hand is preferred over another. It is especially noticeable when completing tasks that require accuracy, speed, or high amounts of coordination (Barr, Rochat & Michel, 2005). On uni-manual tasks (tasks requiring only one hand), the dominant hand will tend to do all of the work, but when tasks require two hands, the non-dominant hand will generally act in a supporting manner by stabilizing or adjusting the object that is being acted upon. Handedness has been studied across a variety of disciplines, including psychology, medicine, anthropology and economy (Johnston, Nicholls, Shah & Shields, 2009).
- 1 History
- 2 Handedness in the Population
- 3 The Development of Handedness
- 4 Theories of Handedness
- 5 Importance of Handedness
- 6 Suggestions for Parents & Practitioners
- 7 References
Hand preference has been thought to exist for over a million years, and was considered to be a necessary distinction before complex human language and fine motor functions developed (Gutwinski, 2011). Throughout history, individuals who were left-handed were stigmatized and discriminated against. An example of this is the use of the phrases “left-handed compliment” or “gauche.” In some cultures, particularly in Asia, the left hand is still considered impure (Gutwinski, 2011). In the past, individuals who were left-handed were considered to have poor coordination and motor skills, but this could partially be due to the fact that the prevalence of right-handed people means that objects and environments are created to be easier for individuals who are right-handed (Tan, 1985). For the same reason, individuals who are not right-handed tend to be at a higher risk for accidents (Gutwinski, 2011). Despite these disadvantages, there is an unusually high proportion of high-performance athletes who are left-handed, as their differences may in fact provide them with a tactical benefit.
Handedness in the Population
Although one may think that handedness is a polar characteristic, meaning that an individual will either be left or right-handed, this is not the case. Multiple studies have shown that handedness exists upon a continuum that is skewed towards right-handedness (Barr et al., 2005). For the ease of interpreting results, many studies will break participants into groups of ‘right-handers’ or ‘left- handers’ but some studies also include groups such as ‘mixed-handed’, ‘weak-right-handed’, ‘weak-left-handed’ and ‘ambidextrous’. Within the general population, right-handed individuals are the majority, falling between 85-90%, with left-handed individuals falling in at the remaining 10-15% (Barr et al., 2005), but this varies between gender and between cultures (Gutwinski, 2011). Individuals who are truly ambidextrous are extremely rare, with the majority of the population having at least a slight preference for one hand over the other. When investigating mixed-handedness, one must also differentiate between inter-task and intra-task stability. An individual who uses both hands, but who always uses the same hand for the same task is different from an individual who will use both hands interchangeably for a single task. In this case, the individual who switches hands according to task is showing a more mature pattern of motor movement (Johnston et al., 2009).
The Development of Handedness
Hand preference has been shown to develop in-utero as soon as fetuses begin to move limbs separately, which is around 9-10 gestational weeks. A study using ultrasound found that the majority of fetuses used their right arm more, with smaller numbers favouring either their left or neither arm (Barr et al., 2005). Longitudinal studies have also shown that prenatal handedness is often fairly stable for fetuses, and hypothesize that it is a precursor to post-natal lateralization (Hepper, 2013). Following birth, the majority of neonates will favour their right arm when producing pre-reaching movements, or swipes towards objects, and will have stronger grasp reflexes with their right hand (Barr et al., 2005). Although there is already a higher incidence of right-handedness, children may still switch back and forth at this time.
As infants approach four months, their reaching will become more refined and by six months, children should be able to grab an object. During this time, uni-manual reaching starts to develop and before children are one year of age, one hand, usually the right, will tend to lead all reaching and grabbing movements (Barr et al., 2005.). By 18 to 22 months, infants have begun to understand more about the demands of a task, and their motor system is developed enough for more lateralization to occur (Rat-Fischer, O’Regan & Fagard, 2013). This means that they may stabilise a bolt with one hand while using their preferred hand to turn a screw. Even before kindergarten, when children are 4 years of age, they will be most proficient with their favourite hand, which can be seen through a variety of tasks such as playing with peg boards or manipulating objects. This degree of preference will continue to emerge until children are at least seven (Barr et al., 2005).
Once hand preference has begun to be distinguished, infants have trouble inhibiting the dominant hand in order to use the non-dominant one in tool tasks. Children who are younger than 14 months old will generally ignore an item’s orientation when reaching, but by 19 months, the majority will use whichever hand is more efficient (Rat-Fischer et al., 2013). What this means is that a child that is 19 months old has to pull something to them with a rake, they are more likely to use their right hand to pull if the object is to the left of the rake, and vice versa. Interestingly, it is the right-handed children who are less able to inhibit the use of their dominant hand in these tasks (Rat-Fischer et al., 2013). This could impact the acquisition of reaching abilities with the non-dominant hand, and is not significantly linked to understanding of tool use. Although the general pattern of development has been outlined above, it is important to remember that each person is unique, and development of hand preference will change from individual to individual. The time, speed, and stability of development vary from child to child and it is common for changes in hand preference to continue well into childhood (Barr et al., 2005). To illustrate this, in a longitudinal study looking at hand preference between the ages of 5 and 11, only 74% of left-handed individuals and 97% of right-handed individuals had remained constant (Barr et al., 2005). Even at an age when children are in schools and using their hands for a wide variety of complex tasks, some individuals are still altering their hand preferences.
Theories of Handedness
There are many theories that try to explain the development of handedness, and the reality probably exists among some combination of them all. This section will highlight some of the most prevalent theories, and is by no means a comprehensive list.
The brain explanation theory focuses on a biological basis for handedness. According to this theory, handedness reflects structural and physiological asymmetries in various motor control areas of the brain (Barr et al., 2005). This means that asymmetries in early fetal sub-cortical development results in asymmetrical hand use by the fetuses. Support for this theory comes from studies on speech and handedness, where hand dominance is thought to reflect hemispheric specialization in the central nervous system. In fact, 95% or more of right-handed individuals are left-dominant for speech. Interestingly, 66% of left-handed individuals are left-dominant for speech, so structural differences cannot be the only reason for handedness (Barr et al., 2005).
The gene explanation also provides a biological basis of handedness. As with the brain explanation, it assumes an association between speech and handedness. This theory posits that a single gene with two alleles controls handedness and speech, where the allele for right-handedness is dominant and represents left-hemisphere control. On the other hand, individuals with the recessive allele exhibit no predisposition to favour one side over the other and so a proportion of them become left-handed (Barr et al., 2005).
There are also two popular environmental explanations for handedness. The first is the uterus explanation, which means that handedness comes as a result of the fetus’ position within the uterus. The most common position for fetuses in the last few weeks before delivery is a left-vertex position, where their back is towards the mother’s left side (Barr et al., 2005). With this positioning, the right hand is able to move more, resulting in right-hand dominance because the position of the mother’s pelvis and backbone would keep the left hand from moving as much. A second environmental explanation is the head explanation. This explanation looks at positioning after birth, where newborns and infants tend to rest with their head to the right (Barr et al., 2005). This means that the right hand is in the infant’s field of vision more often, and so the infant’s hand-eye coordination is initially better with their right hand (Barr et al., 2005).
As handedness is strongest in skills that require more training and practice, education, socialization and culture may be a strong influence on handedness. Barr and colleagues (2005) provide support for this theory by highlighting how left-handed individuals are less common in societies where being left-handed is discouraged or prohibited, and among elderly populations of societies that are now tolerant of left-handedness but that were not in the past. In addition, even societies that are ‘left-hand tolerant’ are designed to be easy to navigate for individuals who are right-handed. This can make it harder to use the left hand, and may completely discourage individuals from using their left hand, which could impact the development of handedness (Barr et al., 2005).
Importance of Handedness
Handedness is linked to many things, including cognitive development. Johnston et al. (2009) associated both left and mixed
handedness with abnormal cognitive development, which may result in either an advantage or a disadvantage to the individual in question. This is evident by the increased chances in developing left-handedness when a fetus or newborn experiences trauma (Johnston et al., 2009). On the other hand, there is a higher proportion of left-handed children classified as ‘gifted’ compared to the general population. This is associated with an increase in verbal reasoning, and right hemisphere dominance, which impacts visuospatial functioning (Johnston et al., 2009). This type of functioning is important for depth perception, which will affect reaching movements and fine motor movements, among other skills.
In addition to cognitive development, sexual development is also associated with handedness. Gutwinski (2011) described left-handed individuals as reaching sexual maturity later than their right-handed peers. This could affect talent identification programs that target girls in their late childhood and early teenage years. Boys tend to reach puberty later, so this would impact them less, but girls who reach puberty later may be able to compete in certain sports such as gymnastics for a longer period of time. Interestingly, studies have found that left-handed individuals tend to be shorter than their peers as well (Gutwinski, 2011).
When comparing handedness, it is important to look at mixed-handed individuals as well. Individuals who are reported as having no hand preference consistently score worse on a variety of measures than their left- or right-handed peers. In addition to performing worse on academic measures, mixed-handed children are lagging behind the others in terms of motor development as well (Johnston et al., 2009). In fact, the same researchers claim that handedness seems to be just as important as maternal education when it comes to child development. Activity-wise, these mixed-handed children tend to spend more time being cuddled by their parents, while left-handed children were more likely to spend time watching television and doing sedentary activities, such as reading, than right-handed children (Johnston et al., 2009).
Coordination and Motor Skills
Historically, left-handed children have been associated with poorer coordination and motor abilities, but this is most likely because their movements look odd to right-handed individuals (Tan, 1985). Children with no strong hand preference do, however, have poorer motor abilities, which could be due to a failure to choose a side. A similar reason can account for the poorer writing skills of left-handed children. In this case, their penmanship does tend to be worse, but it is due to the left-to-right direction used in Western writing and not poor motor coordination (Peachey, 2004). For left-handed individuals, to write in this method requires a pushing movement instead of a pulling movement, a decreased ability to see what is being written, and a cramped writing position (Peachey, 2004).
Sport and Handedness
Sport-wise, literature suggests that left-handed individuals may have an advantage over their peers. As an example, Parish, Baghurst, Dwelly and Lirgg (2013) found that left-handed individuals are more proficient at gaining relevant information on motor skills when the demonstration was performed by a non-dominant hand instructor compared to right-handed individuals. This could be due to more practice as typically demonstrations are performed by right-handed coaches and educators, and/or be a reflection of superior visuospatial skills. Remarkably, the sporting advantage for left-handed individuals is only found in interactive or competitive sports (Grouios, Tsorbatzoudis, Alexandris, & Barkoukis, 2000). Sports that fall under this category include volleyball, boxing, handball, and tennis, whereas sports such as running, skiing, swimming and weight lifting do not show this increase. This suggests that success is not due to superior central motor systems, spatiomotor skills, or increased skill when two hands are required, but that some other attribute must be providing these advantages (Grouios et al., 2000).
So what benefits do left-handed individuals have? They may have the benefit of unfamiliarity, where their attacks and movements will come from different angles and directions than expected when competing against a right-handed individual (Grouios et al., 2000). Left-handed individuals would be more used to fighting against right-handed individuals, and thus would have the tactical advantage of not only knowing what to expect, but also knowing weaknesses commonly found in a right-handed individual. Another advantage, called perceptual frequency effects by Hagemann (2009), suggests that left-handed individuals have an advantage because they are better able to predict their opponents’ movements. This would tie in not only to the superior cross-over skills demonstrated by Parish et al. (2013), but would also include the element of surprise, where right-handed individuals are not as good at ‘reading’ the motions of left-handed individuals. Although there has been little study done on sports, handedness and children, these studies on adult populations suggest a potential method for talent identification, and more studies should be performed on the topic to better understand it.
Suggestions for Parents & Practitioners
- If child is demonstrating left-handedness, there are lots of products that are made for use by left-handed individuals. Stores such as Lefty’s in San Francisco have a wide range of products, from watches to school supplies, that are designed with a left-handed consumer in mind.
- If a movement looks odd, do not immediately discount it as a bad motor pattern. It may look odd because it is mirrored. Look at the end result of the movement and whether it is successful or not.
- Children without a preferred hand may serve as a marker for requiring special assistance with motor skill development so they should be identified and assisted as needed (Tan, 1985)
- When writing, let the child play around with handgrips. If an unconventional writing style allows them to write quickly, relatively legibly and for long periods of time, don’t try to change it. (Peachey, 2004).
- If classrooms or other study spaces have chairs with built-in half desks, make sure that there are sufficient left-handed desks. Having to twist to use a desk with the desk on the right of the chair can result in poor posture and cramped and slow writing.
- If a left-handed child seems clumsier than others, take a look at the environment. It may be set up so that it is easy for right-handed individuals to navigate at the expense of left-handed individuals.
- There are a lot of web resources that discuss handedness. Some are better than others, but websites such as http://www.indiana.edu/~primate/lspeak.html provide insight into what being a left-handed or ambidextrous individual can mean and provides additional tips to try. Not all of the advice will work for all individuals, but they can help with teaching non-right-handed individuals.
- Barr, R., Rochat, P., Michel, G. (2005). Handedness. In The Cambridge Encyclopedia of Child Development. (Vol. 1, pp. 321-326). Cambridge, UK: Cambridge University Press
- Grouios, G., Tsorbatzoudis, H., Alexandris, K., & Barkoukis, V. (2000). Do left-handed competitors have an innate superiority in sports? Perceptual and Motor Skills, 90(3c), 1273-1282.
- Gutwinski, S., Loscher, A., Mahler, L., Kalbitzer, J., Heinz, A., & Bermpohl, F. (2011). Understanding left-handedness. Deutsches Arztebl International, 108(50), 849-853.
- Hagemann, N. (2009). The advantage of being left-handed in interactive sports. Attention, Perception and Psychophysics, 71(7), 1641-1648.
- Hepper, P. (2013). The developmental origins of laterality. Developmental Psychobiology, 55(6), 588-595. DOI: 10.1002/dev.21119
- Johnston, D., Nicholls, M., Shah, M., Shields, M. (2009). Nature’s experiment? Handedness and early childhood development. Demography, 46(2), 281-301.
- Parish, A., Baghurst, T., Dwelly, P., & Lirgg, C. (2013). Effect of handedness on gross motor skill acquisition in a novel sports skill task. Perceptual and Motor Skills, 117(2), 449-456.
- Peachey, I. (2004). Left-handedness: A writing handicap? Visible Language, 38(3), 262-287.
- Rat-Fischer, L., O'Regan, J. K. and Fagard, J. (2013), Handedness in infants' tool use. Development Psychobiology, 55, 860–868. doi: 10.1002/dev.21078
- Tan, L. E. (1985). Laterality and motor skills in four-year-olds. Child Development, 56(1), 119-124.