Why people are left-handed or right-handed?

Answer 1

Handedness is determined when you begin learning to write. Which ever hand you use is your dominant hand.

EDIT

Handedness is determined by which hand is dominant in all activities, not just writing. I'm what's called mixed-handed (cross dominance). I favour my right hand to write with, my left hand to eat with, my right to serve and left to bat in tennis and Badminton. I tie knots left-handed, knit and sew right-handed.

Ambidexterity is a rare form of mixed-handedness, where both hands are equally dominant in most activities.

For general purposes, people say you are right-handed when you write with your right hand, but the strength of your handedness can vary. Though I write with my right hand, I am considered moderately left-handed. I'm not strong in either direction, but tend towards left.

Look at the way you do activities like sports and eating and also DIY work. If your right hand is continually dominant, you are right-handed. If your left hand is dominant, you are left-handed. If both are equal, you are ambidextrous, and if neither are completely dominant, you are mixed-handed.

Answer 2

What determines if a person is right or left hand dominance is the hand they write with. This is a genetically determined preference, with right handedness being the dominant trait. If a person is born with a left handed preference, they can develop more facility with the right hand because of practice. Most left handed people I know are much more ambidextrous than right handed people because of things like scissors and other implements designed for right handed people.

Answer 3

Because it the way your born