[rndmize]

Having worked at a library providing computer tutoring and assistance, I can absolutely believe such studies. You say "using the mouse right-button shortcuts" - the vast majority of people don't know these exist, or if they do, no idea how to use them (or what a "context-sensitive" menu is). When I guide my grandmother through something over the phone, I often have to specify whether she needs to click or double-click something - which I find so obvious now as to not even think about. Go figure.