This is from the interview with Miyamoto in the Edge Magazine:
Splatoon and the three prototypes are the first games to emerge from Garage, a new Nintendo development programme set up last year in which developers break off into small teams and work on new ideas. "There are increasing numbers of young staff at Nintendo's development studios these days," Miyamoto says, "and these young guys really want to express themselves." Work is done during office hours, but he compares Garage to an after-school club, in spirit if not in schedule. "Class time's over: they gather together and think about new projects completely apart from their everyday business assignments. When all of those projects have advanced to a certain stage, we gather together and exchange opinions on the outcome of each of them, and together we decide which ones should continue. We may have shown several software titles at E3 [that came from Garage], but there are many others in development too.