You can see this most clearly when you take away someone's watch and you shut them into a bunker, deep underground, for a couple of months.  People actually volunteer for this, and they usually come out kind of raving about their productive time in the hole.
体内時計をはっきり観察するには 時計の無い 地下深くの穴ぐらに 誰かを二、三ヶ月間 閉じ込めてしまいます ボランティアが実験に協力しますが 穴の中での生産的な生活に 大喜びで出てくるのが普通です