Dominance - what is right?


Compiled by Deanna Iris Sava, MS, OTR/L 

Mary Benbow stated that handedness depends on neurological inhibiting of the recessive (non-dominant) hand, so that the dominant hand can develop the precise, corrective, rapid movement without synkiknesis or competition from the non-dominant hand. According to Rhoda Erhardt, the process of inhibition can also be described as dissociation, which comes in developmentally as the infant moves from bilateral and symmetrical to unilateral and asymmetrical stages.  Mary Benbow believes that the wrist must be properly positioned and stable in extension or poor habits will follow the child throughout his/her life. The wrist and hand are one physiological unit and must develop together. Working on a vertical surface will correct the wrist position. The thumb triad of muscles must be active or the child will develop substitute muscles that do not serve him/her well when a higher volume of writing is demanded. This will depend on pontine-cerebellar maturation of the cortical spinal system.

It is also important to note that not all body dominances (hand, leg and eye) are same-sided. Leg dominance is dependent upon whether the leg is stabilizing or moving. Many postural factors affect which leg a child will use to stabilize or weight bear on when doing leg activities, especially in contrived situations. There could be mixed hand dominance; e.g., a dominance for reaching out, a different dominance for tool manipulation, or even different dominances for different tools (scissors, pencils, etc.). Cutting and writing with different hands is often observed in children who prefer the opposite hand for sports activities. This is not considered abnormal, but rather one side has developed greater strength (and that hand is used for coloring, ball throwing, etc.) and the other hand has developed greater fine motor control /dexterity (used for writing/cutting). If a child uses one hand consistently for certain tasks, and the other consistently for other kinds of tasks, this is called crossed dominance. An indication of not having an established hand dominance occurs when a child constantly switches hands and uses either hand for similar tasks. The literature suggests that crossed dominance is common and is not necessarily indicative of a problem. If students with crossed dominance are functional, it is not necessary to try to change this use, although the underlying problem may be addressed if it is causing a true functional deficit in another performance area. Handedness is comprised of hardware (musculoskeletal, strength) and software (neurological), interacting to produce an efficient response system.

If a child switches hands, it prevents the establishment of an efficient synergy for response.  Jan Olsen (Handwriting Without Tears) suggests that a child should learn to print with one hand. Otherwise, switching cuts the practice benefit. In cases where a child switches hands, Jan suggests evaluating the child's skills with both hands to decide which hand is more skilled for handwriting. Watch how child picks up, holds, and moves the pencil, uses the helping hand, etc., and note which hand is better at writing. Pick the more skilled hand and try to encourage use of that hand. In addition to pencil use, it would be beneficial to include tool use and play activities in determining which hand is more skilled.


Q. What is the difference in meaning between these groups of words?

Hand dominance, handedness, and hand preference
A. Hand dominance means that one hand has the most influence or control. Handedness means that one hand is more reliable for use   across a range of skillful acts. Hand preference means that one hand is preferred or chosen.

Ambidexterity and mixed dominance
A. Ambidexterity is defined as the ability to use both hands equally well, an unusual skill in the normal population. The term mixed dominance has been used to describe a confusion or delay in the development of hand dominance in persons with disabilities.

Q. When does hand dominance emerge in normal development?
A. According to Dr. Arnold Gesell, the developmental progression in the first year begins with use of one hand, then the other, then alternating hands, and then using both hands together, first symmetrically (about 4 months), then one assisting the other (about 1 year). Tasks requiring each hand to perform different skilled movements develop during the preschool years and beyond. A majority of children show a preference by age 3 and most by school age, but Dr. Gesell wrote that hand dominance doesn't become well integrated in some normal children until eight or nine years of age (Gesell & Ames, 1947). It is also true that some adults demonstrate skillful ambidexterity, especially in sports.

Q. What affects hand dominance more: genetic or environmental factors? Does this differ in children with disabilities?
A. It is generally agreed that genetic factors play the most important part in determining handedness. However, situational or environmental factors such as the task (precision or power), the materials (size, shape, weight), and positioning (child and object) affect choices for reaching/grasping, lifting/carrying, and unilateral/bilateral hand use. Children with disabilities usually have one arm/hand that is less affected than the other. Thus, despite genetic predisposition, they choose the limb that is most efficient. However, even they demonstrate choices based on situational factors, such as using one hand for distal tasks such as finger feeding, and the other hand for tasks requiring skills in more proximal movements such as shoulder/elbow/wrist control during utensil use. In fact, studies have shown that handedness is simply not a unidimensional trait, since specialization for the control of distal and proximal musculature may be located in different hemispheres. Thus behaviors that rely upon axial musculature and involve strength more than dexterity show less laterality bias than fine motor behaviors such as writing (Healey, Liederman & Geschwind, 1986; Peters & Pang, 1992).

Q. How do left-handers compare with right-handers in functional performance, and why should we be knowledgeable about the differences?
A. A large number of research studies have found that the number of left-handers is greater in persons with learning disabilities. Even studies of individuals without disabilities show that right-handers do better than left-handers academically, but those differences are not apparent until adolescence. However, in young children, handedness is seldom found to be related to learning or problem-solving abilities (Coren, 1992). Elementary age right-handers and left-handers performed equally well on the Southern California Motor Accuracy Test (Smith, 1983). We should understand the problems experienced by normal left-handers in a primarily right-handed society (writing from left to right, using scissors, operating zippers, etc.), since so many children with disabilities have less involvement on the left side (due to greater incidence of left hemisphere damage). In other words, some of their functional problems may be due to the use of the left hand, rather than the disability.

Q. Is it important for eye, hand, ear, and foot dominances to be congruent?
A. According to the literature, 75% of the normal population has eye-hand congruency, 63% have congruent ear and hand, and 85% have congruent foot and hand. Crossed eye-hand dominance may be more efficient for certain activities such as batting a baseball.

Q. If a child keeps alternating hands when writing, how do we determine which hand should be used? What are the implications of unclear or mixed dominance for academic performance?
A. "Mixed dominance" may be a symptom of dysfunction rather than a cause. A study of children with mild neurological impairment from early brain insult showed that the right-handers and those with mixed handedness did equally well in school (Saigal, et al, 1992). So, we must first determine if the actual products (handwriting and content) are functionally inadequate. If so, we need to analyze the child's posture and movements, the nature of the task, and the characteristics of the environment. Those clinical observations and specific evaluations can be recorded on forms such as the Documentation of Hand Preference and Quality of Performance Chart, the Erhardt Developmental Prehension Assessment (EDPA©)(Erhardt, 1994), and the Erhardt Hand Preference Assessment (Erhardt, 1998, 2003). From that information we can plan intervention consisting of activities that 1) remediate missing developmental components, and 2) adapt the environment to enhance function.

Q. What are some examples of missing developmental components and environmental adaptations relating to incomplete acquisition of hand dominance, and the appropriate interventions?
A. Essential developmental components include postural control, eye-hand coordination, unilateral/bilateral/bimanual function, and perceptual concepts (body image, laterality, and internal/external directionality). However, opportunities should also be provided for non-directed exploration of objects/materials, a natural way for children to follow the normal developmental progression toward handedness (Knickerbocker, 1980). The purpose of intervention is to remediate motor development so that the brain can continue with its maturational goals of 1) establishing at least one hand for skilled work, and 2) the ability of both hands to interact for a variety of tasks. If those developmental components are very delayed or permanently impaired, environmental adaptations include postural supports in floor, sitting, and standing positions and adapted clothing/toys/tools for feeding, writing, etc. These adaptations should be constantly modified, as the child's needs change.

Several occupational therapists contributed to the ideas that were compiled into this document related to hand dominance. A partial list of books, articles, and videos includes:

Bishop, D.V.M. (1990). Handedness and Developmental Disorder. Philadelphia: J. B. Lippincott Co.
Gesell, A. & Ames, L. B. (1947). The development of handedness. The Journal of Genetic Psychology, 70, 155-175.
Erhardt, R. P. (1994). Developmental Hand Dysfunction: Theory, Assessment, and Treatment (2nd ed.). San Antonio: Therapy Skill Builders.
Erhardt, R. P. (1999). Normal Components of Hand Preference (video). Maplewood, MN: Erhardt Developmental Products.
Erhardt, R. P. (2000). Normal and Atypical Hand Preferences (video). Maplewood, MN: Erhardt Developmental Products.
Guiardin (1987). Asymmetric division of labor in human skilled bimanual action. Journal of Motor Behavior, 19(4), 488.
Hicks, R. E. & Kinsbourne, M. (1976). On the genesis of human handedness: a review. Journal of Motor Behavior, 8, 257-266.
Levine, K. J. (1991). Fine Motor Dysfunction: Therapeutic Strategies in the Classroom. San Antonio, TX: Therapy Skill Builders.
McCartney, G. & Hepper, P. (1999). Development of lateralized behaviour in the human fetus from 12 to 27 weeks' gestation. Developmental Medicine & Child Neurology, 41, 83-86.
McManus, Chris (2002). Right Hand, Left Hand: The Origins of Asymmetry in Brains, Bodies, Atoms and Cultures. Harvard University Press.
Murray, E. A. (1995). Hand preference and its development. In Henderson, A. & Pehoski, C. (Eds.). Hand Function in the Child (pp 154-163). St. Louis: Mosby Year-Book, Inc.
Rosenbloom, L. & Horton, M. E. (1971). The maturation of fine prehension. Developmental Medicine and Child Neurology, 13, 3-8.
Saida, Y. & Miyashita, M. (1979). Development of fine motor skill in children: Manipulation of a pencil in young children aged 2 to 6 years old. Journal of Human Movement Studies, 5, 104-113.
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