Most parents notice their toddler starting to favour one hand, sometimes as early as 18 months to two years, and wonder whether this is significant or whether they should be doing anything about it. A smaller group of parents have children who seem to use both hands indiscriminately well into the preschool years and wonder whether something is delayed.
The short answer in both cases is usually to observe and not intervene. Handedness is a neurological characteristic that reflects underlying brain lateralisation, it develops on its own timeline, and attempts to influence it are ineffective and can cause harm.
Healthbooq (healthbooq.com) covers motor development and developmental milestones through the early years.
How Handedness Develops
In the newborn period, there is no meaningful hand preference. Infants use both hands in the symmetric fashion dictated by early reflexes.
Between about 6 and 12 months, some infants begin to show mild preferences for one hand over the other in particular tasks, though these early preferences are often inconsistent. Most children at 12 to 18 months still switch between hands depending on task and approach.
Between 18 months and three years, a preference typically begins to emerge more clearly. The child starts to reach consistently with one hand, to hold a spoon or crayon consistently with one hand, and to use the non-preferred hand more often for stabilising tasks.
By four to five years, most children have a clear, established hand preference that is consistent across tasks. This is the age at which the preference is well enough established to be reliably assessed.
About 10 per cent of the population is left-handed, a proportion that has been remarkably stable across cultures and across history. Right-handedness is more common, reflecting that the left hemisphere of the brain (which controls the right side of the body) is dominant for language and fine motor control in the large majority of people.
What Influences Handedness
Handedness is substantially genetically determined but not completely so. Identical twins share handedness in about 75 per cent of cases, which indicates a strong but not determinative genetic contribution. Environmental factors are less clear.
Theories about fetal position, prenatal hormone exposure, and birth complications having effects on handedness exist, but the evidence is not strong or consistent. What is clear is that handedness is not something parents can meaningfully influence through which hand they offer things to, or which hand they encourage a child to use.
Left-Handedness
Left-handedness has no negative implications for development, intelligence, or ability. In fact, left-handed individuals are slightly over-represented in certain creative and spatial professions, though the reasons for this are debated.
The main practical implication of left-handedness is environmental: scissors, writing implements, and many tools are designed for right-handed use. Left-handed scissors, which genuinely cut differently from right-handed scissors (rather than just having the handles mirrored), are worth having. Pen grips and writing tools designed for left-handers are available and helpful as writing develops.
At school, sitting position matters for left-handed children. A left-hander seated directly next to a right-hander at a table will elbow-clash constantly; seating a left-hander at the left of a pair solves this.
The script orientation in English goes left to right, which means left-handed children write toward the side where their hand has already been rather than ahead of it, which can cause smudging and the "hooked" wrist position many left-handers adopt to see what they have written. Positioning the paper at a rightward angle (counterclockwise) reduces the need for the wrist hook.
When to Be Curious
Most variability in hand preference development is entirely normal. However, some specific patterns are worth noting to a health visitor or GP.
Very strong hand preference established very early, particularly before 12 months, can occasionally indicate reduced function in the opposite hand. A child who never uses their left hand at all, for example, might be showing a subtle hemiplegia (one-sided weakness) rather than natural early preference.
No clear preference by age six to seven, if combined with significant difficulty with fine motor tasks (drawing, cutting, self-care), may be worth assessment for developmental coordination disorder (DCD) or other motor difficulties.
Mixed laterality (using different hands for different tasks in an inconsistent way beyond the early preschool years) is common and usually benign, but when combined with other developmental concerns warrants assessment.
Key Takeaways
Hand preference emerges gradually in the toddler and preschool years, with most children showing a clear and consistent preference by age four to five. Some children remain ambidextrous much later. Neither left nor right handedness confers developmental advantage or disadvantage. Attempting to alter a child's natural hand preference is ineffective and counterproductive. Persistent inconsistency of hand use, or very late establishment of preference (beyond age six), may warrant assessment, as it can occasionally reflect underlying motor or neurological differences.
