eli5 – What’s the science behind a person’s dominant arm?

Question

I’ve always wondered why people were usually stronger or more dexterous with one hand. Is the muscle thicker there or something?

In: 18

Answer 1

The [wiki on dominant hand](https://en.wikipedia.org/wiki/Handedness) has a section on causes.

Mostly these are untested opinions based on different theories of cognition and the brain side of the event.

* Language dominance – language, speech and writing are so complex that gross motor skills are in the other side of the brain.

* Genetic factors – if both parents are left handed, the chance of the child being a leftie goes up to 26% (compared to 9% in population)

* Environment – Twin studies indicate that genetic factors explain 25% of the variance in handedness, and environmental factors the remaining 75%

* prenatal hormone exposure – studies show exposure to diethylstilbestrol (synthetic estrogen) were more likely to be left-handed over the clinical control group.