AdvertisementWant To Teach Your Kids Self-Control? Ask A Cameroonian Farmer02:42Download AudioResumeJuly 03, 2017Michaeleen DouclefffacebookEmailGerman and Cameroonian kids were part of an experiment based on the classic "marshmallow test": Put a single treat before a child but tell the child if he or she waits, say, 10 minutes, a second treat will be given. (Nathalie Dieterle for NPR)