《毛诗序》说:“情动于中而行于言,言之不足,故嗟叹之,嗟叹之不足,故咏歌之,咏歌之不足,不知手之舞之,足之蹈之也。”这说明人在非常激动、内心情感用言语甚至唱歌都难以充分表达的时候,这种蓄积已久的情感会情不自禁地通过手舞足蹈来抒发。而“咏歌”与“手舞足蹈”之间的待变状态就是所谓的“临界点”。 “Maoshi Preface” said: “Emotion in the line and in the words, the lack of words, so sigh of sigh, sigh of inadequate, so the chant song, the lack of chant song, I do not know the hand of dance, Also. ”This shows that people are very excited, the inner emotion of words and even singing are difficult to fully express when the long-awaited emotion can not help but express themselves through dancing. And “chant song” and “dancing” between the state of change is the so-called “critical point ”.