Developing a dominant hand

Around 3 years old, the child starts to develop a dominant or preferred hand to use. However, the child will commonly swap hands at this age until their hand preference is fully established by about 4 to 5 years old. A few children will not fully display a dominant hand until the age of 8 years old. In the general population, the proportion of people who are left handed is estimated to be around 10%.

The development of hand dominance reflects changes in the brain. Each hand is controlled by the opposite side of the brain. They communicate via a link known as the corpus callosum. To begin with both seem to perform similar functions, but as specialisation within the brain occurs their functions diversify.

When a child is learning to write and writes a letter backwards, this reflects the fact that the motor signals for writing are coming from the opposite side of the brain to normal at that instance.