Mothers. Mothers are — probably quite literally — genetically coded to bug take care of their children. Part of this parental process is calling the child regularly if the child lives away (sometimes it involves calling the child regularly multiple times a day). Or at least that is how it used to be. With the advent of social networks, email, smartphones, etc. there are so many more ways for a mom to get in touch with her child; check it out:

[via C-Section Comics, Geeksaresexy]