What hand do you use to control your computer's mouse? Most computers are set by default to have the mouse to the right. This can be useful for lefties if you are taking notes or writing while you are also using the mouse, as you can do it with your left hand.
On the other hand (!) Most lefties have better fine control with their left hand, so they would prefer to have the mouse to the left. Some lefties simply put the mouse to the left and leave the buttons set to their default value, with the main "click" button still being the left one and using it with your middle finger (this does not apply to Apple Macs that do not have 2 buttons mouse).
It is more common to change the mouse buttons, so the left index finger still makes the main click and this can easily be done in Windows ...
Home / Settings / Control panel / Mouse /
and in the Buttons tab, check the box "Change primary and secondary buttons"
This can cause problems if you share the computer with a right-handed person. Mauricio Tejada in Japan has produced an intelligent utility that allows him to instantly exchange the mouse buttons with left or right handed users simply by pressing Ctrl-F12 instead of going through the Windows Control Panel.
1Wouldn't someone who is left handed change that on a system level so you would be reversing that change? – Seth – 2016-11-30T07:51:04.433