translation.en: So, for example, I was giving this talk recently in New York City, and I said, "You know when you're on the subway and the other person across the subway car smiles at you, and you just instinctively smile back?"
translation.zh: 打个比方来说， 我最近在纽约市演讲， 其中说到：“当你在地铁上， 车厢对面的人 向你微笑时， 你会下意识地回报以微笑。”