Some basic mental skills seem to get rusty from lack of use. Like doing math in your head, composing thoughts on paper, knowledge of geography and others. It is obvious that our calculators, computers and instant voice communication especially have made the mastery of these things somewhat unneccessary. Too bad. I sometimes believe it undermines our ability to think. What is the point of a child being taught to tell time by an analog clock?
Physical skills, once learned, seem to be remembered by the body, like riding a bicycle. I had occasion to drive a stick shift auto recently and even though I have not driven one in years it came to me without a second thought.