Ravelli ( 1988 ) points out that the large existence of grammatical metaphor in a discourse increases the difficulty of the discourse itself , and decreases the reading speed of learners , thus reduces the intelligibility of the discourse and decreases the language input for learners .

Ravelli（1988）同时指出，语法隐喻在语篇中的大量存在，增加了语篇自身的难度，同时降低了学习者的阅读速度，最终阻碍了学习者对阅读材料的理解，因此极大地制约了学习者语言能力的发展。