Hand dominance and hand preference are terms that refer to a person’s consistent use of one hand rather than the other hand for a skilled task
The human brain is divided into two cerebral hemispheres that are specialised to perform different tasks (such as language and spatial reasoning*), and yet also work together when both sides are needed to produce the best results in physical and mental tasks.
Both hemispheres have an area called the motor cortex. When it comes to moving the body, the left motor cortex controls movements on the right side of the body, and the right motor cortex controls movements on the left side of the body.
Being able to use a tool with the same hand consistently and in a precise way (such as drawing with a pencil, using a screwdriver, cutting with scissors) can be an indication that the hemispheres of the brain have become specialised, or lateralised, for a specific function.
Children who don’t have a strongly specialised left or right hand for a specific task, who switch hands when a specialised hand is required, may struggle to carry out fine motor tasks that require automatic, learned movements, such as cutting neatly on a line with scissors, or handwriting.
The more a child uses a specific hand for a task, the more efficient the child becomes at that task, and then the movement becomes “automated”, which frees the brain up for other cognitive tasks.