Ambidexterity

How it works

About 90% of people are right-handed². Handedness comes from the way the two halves of the brain divide up fine motor control. It shows up before birth and is stable for life in most people.

Genes play a part but not a large one. Twin studies put the inherited share at about 25%, with the rest coming from development and environment². A 2020 study of 1.7 million people found 48 genetic variants linked to handedness. Of these, 41 were tied to left-handedness and 7 to ambidexterity².

True ambidexterity means equal skill with both hands for every task, including writing. Fewer than 1% of people have it¹. Mixed-handedness is much more common. A mixed-handed person writes with one hand and throws with the other, or uses scissors with the left and a fork with the right³. Many people who call themselves ambidextrous are mixed-handed.

The non-dominant hand can be trained. Musicians, surgeons, and athletes do it on purpose. People who injure their writing hand usually learn to write with the other within months. The trained hand rarely reaches full equality.

Try it

1. Write your name with your usual hand, then with the other. Compare.
2. List five tasks: throwing a ball, using scissors, brushing teeth, opening a jar, dealing cards.
3. Note which hand you reach for in each one without thinking.
4. If the answers are all the same hand, you are strongly one-handed. If they split, you are mixed-handed. If both hands do every task equally well, you are in the rare group.

History and culture

The word comes from Latin: ambi, both, and dexter, right. It means having two right hands¹. Leonardo da Vinci wrote with his left hand in mirror script and is often described as ambidextrous⁴.