Some children choose their dominant hand very early. You may notice your son or daughter using their right hand more often when they are as young as 7-9 months. This may not be permanent, though. The majority of the time, children begin to display permanent hand dominance at around 2-years-old. For some kids, it could be when they are 4 to 6-years-old. When children begin learning to write in school, their teacher may note that they have not yet chosen a dominant hand. Some never do and will be ambidextrous or mixed-handed. Fun Fact: In about 20% of identical twin children, one twin will be left-handed and the other twin right-handed.