On One Hand or the Other: What we know about mixed-handedness

My handwriting was so bad that my teacher told me to try writing with my left hand. That seemed to work. It must have been first or second grade, but that day I was left-handed. When I got a little older, my throwing was so bad that my dad told me to try throwing with my right hand. That seemed to work too. Every day after that, I’ve been confused.  As a kid trying out for sports, I felt cursed. I was called ambidextrous, but I was really just not dexterous.

Ambidexterity is defined as the ability to use both the left and right sides equally well for any given task. In reality, this is not a naturally occurring gift. This is a learned skill that takes years of practice and training.

Instead, everyone displays degrees of dexterity. Better names for “ambidexterity” would be Mixed-Handed. Every mixed-handed person is different in that they use each hand for different activities as opposed to both hands for the same activities.

Most of the world falls under the broader label Single-Handed. About 90% of this population identifies as being right-handed, and the other 10% identifies as being left-handed.

So why are humans like this? Why have we evolved to prefer the use of one hand over the other?

Humans likely evolved to be single-handed because it offered the quickest means of learning a skill (Uzoigwe 2013). This is the specialization hypothesis: If every day I practice swinging a club with my right arm, I strengthen my right arm. As my arm gets stronger, I get better at swinging my club. If I wanted to switch to my left arm, there is a greater startup cost to training. If I want to make my left arm just as strong, I need to spend perhaps an equal amount of time to strengthen it as well.

In a survival setting, time is a luxury. A mixed-handed person will be weaker and less likely to survive. Short-term competition favors the specialized, single-handed person.

There are strategic advantages for each hand preference:

  • Right-handed people’s motor functions are generally faster
  • Left-handed people are less predictable in a fight and are more likely to win
  • Mixed-handed people are better equipped later in life to train to be ambidextrous.

Page 2: Research Limitations