1.2 Research Significance 1.2.1Theoretical Significance

First of all, this thesis can help theory of metaphor develop and spread. The study of cognitive metaphor originates in the United States. Until the last century 90s, it spreads into China. Our country soon arises the highlight of study on cognitive linguistics, but research is not deep enough in essence. This status will become the bottleneck of metaphor theory and is bad for development of metaphor theory in our country. As a new field of linguistics research and a new research angle, metaphor theory needs different language corpus to test. On the one hand, it can verify the application range of metaphor theory. On the other hand, it can promote continuous development of metaphor theory within a wider field.

Moreover, this thesis can open up the research field of English public service advertisements. English public service advertisement starts relatively late compared with commercial advertisements.  The world's first public service advertisement appeared in the 19century 40s in the United States. So it is also a little late to study and analyze English public service advertisements. With the development of social economy,  there are increasing numbers of English public service advertisements. People also have more and more high requirements for English public service advertisements. This will largely promote in-depth study on English public service advertisements. In fact, there is a rapid development on study of English public service advertisements. Especially since the 21st century, study of English public service advertisements also shows a tragedy of quick development. It not only gets fruitful researches, but also spreads into a wide field. Metaphor is a basic way of human’s thought and cognition. Human recognizes unknown things with the method of metaphor.  So  from  the  cognitive  perspective,  it  can  provide  a     new thinking for the research of English public service advertisements. 

1.2.2Practical Significance

English public service advertisements is an important carrier of advertisements to achieve its social value. An impressive piece of English public service advertisements can resonate in the hearts of audiences. Conceptual metaphor can help audience think about the message in deep hearts, and further help them to improve social and public environment. Within the category of cognitive science, metaphor is not a kind of rhetoric way, but a way of human thinking.

Human thinks about the problem in a metaphorical way of thinking and recognizing unknown things. Even today, science is developing quite quickly, and we still use metaphors to perform thinking activity. Thus, metaphor is playing an important role in our daily life. English public service advertisement inevitably uses metaphor in the cognitive style. Based on the reality of metaphor in English public service advertisements, metaphor can make the creation of English public service advertisements more close to person's psychology, more easy to accept, to better achieve social value of English public service advertisements.