At a healthy and physically fit 68 years of age I find, for me, an intense interest in self-experimentation about this topic. I have myself as a subject and only need my best effort, honesty, journaling and a few questions to do lab work. The questions include “what deeply held views have change today?”, “what concrete evidence such as changed choice or altered action did I do today?”, “what uncomfortable choice of positive new behavior did I do today?” … and so forth.