HANDEDNESS: Right or left?
Dr Elke Kraus
Have you ever wondered whether a child is left or right-handed? Or ambidextrous? Or seemingly undecided as to which hand to use? As a paediatric occupational therapist, I did a lot of wondering about children who swapped their hands across and within activities. It puzzled and fascinated me so much that I started researching handedness in children as far back as the 1990s. And the more I learnt about handedness, the more complex but also revealing it became. It seems appropriate to share some of the things I learnt about handedness on Left Handers’ Day, particularly since some left-handers are still at risk of being made to write with their non-dominant right hand.
Actually, when handedness is established (as it is in many if not most children entering school), it seems a simple phenomenon at first glance. Right-handed children prefer to use their right hand for most tasks and are better with it, and left-handers use their left hand more often and more proficiently. Children with clearly developed handedness and good motor skills usually master everyday activities without problems. But there are some children whose dominant hand is not yet clear. They keep swapping hands, which impedes their skill acquisition and ability to automate movement. These children often avoid fine motor skills because they are difficult. So if you ever wondered if fine motor skills and hand preference have a connection – yes they do!
Once you start to look more closely at how we perform tasks, you realise that most of them involve two hands (i.e. bimanual). In terms of handedness, this means that the two hands have to take on different roles. The genetically dominant hand is usually the more active one performing the task, whilst the non-dominant hand stabilises or assists. The nature of the activity also influences which hand is used. And if we think which activities are practised and automated because they have been repeated so many times, it is also most likely that the same hand will continue to be used. Also, simple spontaneous tasks are more easily performed with either hand, whilst the demanding tasks are not. So the type of task and task demand also influence hand use.
Another strong influencing factor on which hand is used, is the environment, which has a clear right-ward bias. If you are a right-hander yourself, you will probably not be aware of it, but left-handers will tell you a range of activities that are designed for right-handed people: measuring with a ruler, spiral exercise books, playing cards, etc. As a result, many left-handed people adapt and perform some or even many of these activities with their right hand.
And then there is a fascinating finding from the literature, that not only do we inherit a left or right-handed predisposition (i.e. direction), but we also inherit how strongly we are right or left-handed. For example, those with a high degree of left-handedness will perform virtually everything with the left hand, and may feel somewhat “disabled” in a right-biased world. But there are a large number of left-handers who display a mild (but definite) degree of left-handedness. They will clearly write with the left, but perform many other activities with the right, and will show no difficulty with any of them. Left-handers as a group show a much greater variety of degree compared to right-handers, who tend to have a moderate to strong degree of handedness.
To make things even more complex, we need to look at the motor aspect in relation to handedness. Importantly, handedness has two aspects which may not always be on the same side: hand preference (how often a hand is used compared to the other hand), and hand proficiency (how well one hand performs in relation to the other). If motor proficiency is good, this will assist children in learning movement patterns and automate tasks on both sides without difficulty. If motor proficiency is poor, the opposite will be the case. Motor problems may also not be the same on both sides. So, what happens when the dominant hand is actually poorer in tasks that are demanding? This may lead to a child using the better but non-dominant hand for complex fine motor skills such as drawing and writing.
As occupational therapists we have specialised in working with children to improve their fine motor skills and handwriting, particularly to get children ready for school. So if a child still swaps hands when drawing, it is often the OTs that help decide on the writing hand. Now here is another crucial bit of information from the research: Did you know that if the non-dominant hand is used for writing (it is also called “converted” or switched-handedness), this may have serious switching consequences, affecting fine and gross motor skills, learning abilities, affective traits, and somato-visceral aspects? In particular, it is left-handed children (often with a milder degree of handedness), that are at risk of being switched. This puts quite a responsibility on professionals making decisions on the writing hand.
So what to do? Should we just leave these kids in the hope that one day the dominant hand will emerge? Or is it in any case better to train the right hand as early as possible, since we live in a right-biased world? Or maybe it does not matter if a child swaps hands, and he/she could just be left to figure things out for him- or herself?
These are not only interesting but also important questions. Since we also strive to work in an evidence-based way, it makes sense to look at research studies to see if there are any guidelines on how to assess and treat children with swapping hand use.
Those who embark on such a journey find themselves in a jungle of research studies, mainly in the field of neuro-psychology, with often confusing and contradictory results. They often seem to raise more questions than they answer. Is the preferred hand necessarily the better one? When should handedness be developed? Is it OK if some people swap more than others? How are motor skills and handedness related? Does midline crossing have anything to do with handedness? Should left-handers do everything with their left, and right-handers everything with their right hand, or is it OK to change hands? Should we test handedness unimanually or bimanually? What is more important: motor proficiency or hand preference? And what kind of tasks are most suited to be used to assess handedness?
In my PhD and post-doc research I found some fascinating and important facts that are summarised below.
- Handedness develops from an initial genetic predisposition, closely intertwined with fine motor development, and emerges from the interplay between inherited (genetics), learned (environment) and development (motor) dimensions.
- Even though no gene has been found to date which passes on left-handedness, there are about 40 different loci (alleles) that have been associated.
- It is possible for two right-handed parents to have one or more left-handed children.
- Physical and socio-cultural environmental aspects influence the development of handedness and can change the direction (i.e. left or right). Indeed, the more formal the culture, the greater the chance that left-handed people will be trained to the right (switched left-handers), particularly with regard to handwriting.
- Handedness does not only present in one of two directions, left or right, but the degree (i.e. how strongly one is handed) also plays a role, and is also inherited.
- There is a group of left-handers who have no problems in any way, who perform many skilled tasks with the right hand (e.g. cutting with scissors, playing tennis).
- In some cases, the genetically dominant hand is also the weaker, less proficient hand. As a result, the non-dominant hand is often used for highly skilled tasks such as writing. This is called “pathological” handedness.
- Switched left-handers with a strong degree of handedness in particular, do not cope well and show switching repercussions, particularly if motor skills are not well developed.
These are some useful building blocks when trying to understand handedness. But how can we find out what degree of handedness a child has, or whether preference and proficiency are on the same side? For this a comprehensive and reliable assessment is needed that can differentiate between various degrees and possibly types of handedness. Since I could not find an assessment for children with atypical hand use that could provide the information needed to base decisions on, I developed the Handedness Profile (HP) in my PhD.
I tried to incorporate all the important findings from the handedness literature. The HP measures not only the direction but also the degree of handedness, and it differentiates between trained and untrained aspects in both unimanual and bimanual tasks. Furthermore, it compares hand preference and performance and incorporates crossing the body midline as a dimension of hand preference. Altogether there are seven subtests: untrained and trained hand preference; untrained proficiency (hammering and tapping); trained proficiency (tracing and dotting); crossing the body midline preference; and bimanual cooperation. In addition, relevant contextual factors and observations are also recorded and incorporated into the scoring, and there are a range of analytical and interpretation tools for the administrator, including a digital scoring template. Testing a child takes between 60 and 90 minutes, and a profile is generated.
Having offered courses to hundreds of therapists, incorporated their feedback to refine the assessment and analyse the handedness cases, it appears that the Handedness profile provides a good basis to understanding why a child swaps hands, whether she or he is left or right-handed, how strong the degree of their handedness is, and which hand the child should be writing with. From this information, the treatment approach can be tailored and specified to the needs of the child.
But not everybody wants to specialise in handedness. For those who merely want to find out whether the swapping they see is OK or whether it is not, there is a screening tool for teachers and parents (see https://thehappyhandwriter.co.za/product/how-to-determine-hand-dominance/). And of course, if you are interested you can read the book on the theory, research, and development of the Handedness Profile, including real case studies and treatment approaches of children with different handedness types. It is called “Beyond left and right handedness – a practice-based approach to assessing and analysing handedness dimensions and types” (2023) https://link.springer.com/book/10.1007/978-3-031-24389-9
I hope that this has been useful information that will help you deal more confidently with those swapping-hands kids! In particular remember, that there are a number of left-handers who use their right hand in many activities very proficiently, but they write with the left, and that is absolutely fine!
Dr Elke Kraus holds a PhD in Occupational Therapy from the La Trobe University,
Melbourne, Australia, where she developed the first version of the Handedness Profile. She qualified as an OT at the University of Cape Town in South Africa. Since then she has practised, researched and taught in the field of paediatrics in South Africa, Australia and Germany. Currently, she holds the position of Professor of Occupational Therapy and Chair of the Physio-/OT Department at the Alice-Salomon University of Applied Sciences in Berlin. Her research interest and focus are the development and validation of analogue and digital diagnostic tools; handedness; fine motor and handwriting skills; school-based occupational therapy; interprofessional learning and working, evidence-based practice combined with a top-down participation-based approach. Email: haendigkeitsprofil@yahoo.com