主题：【整理】全球化与英语--纽时书评摘录 -- 元亨利

In the popular American sit-com Friends, there is a scene where Phoebe tells Rachel, “They don’t know that we know they know we know. ”

Why we human beings turn to this kind of tongue twisting? Enter science......

Here is the link to the article in The New York Times that might just answer that question.

Next Big Thing in English: Knowing They Know That You Know