[antisthenes]

I have acquired this habit from the 2 years I've spent playing Starcraft : Brood War and Starcraft 2 semi-competitively.

In the game you have to select units by dragging a box around them, and that habit has carried over to selecting text on the screen in pretty much every computer application.

I know that probably doesn't answer your question, but that would probably require a neuroscientist. It doesn't help me read personally, it just seems to be one of those repetitive tasks that slightly autistic people do.

Some of my coworkers share this habit as well, and they've never played RTS games, so it's acquired in different ways.