Concentration.

Lovely review in the Wapo of a book called "Rapt", whose thesis is that noone concentrates on anything any more. (See also the mythology around multi-tasking. I don't think you can do two things at once if one of them requires much mental effort. And don't get me started on the connection between this and the gender sterotype....)

Anyway, the reviewer says:

Spending an hour doing just one thing -- such as reading a book or practicing a musical instrument -- may soon be the equivalent of wearing spats