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The Metaphorical Interpretation of English and Chinese Body-part Idioms Based on Relevance Theory

As a special language coding way and language phenomenon, metaphor is an important form when humans use language in communication. However, metaphorical mappings are not arbitrary. They are based on our physical experience of the world around us. Idioms are the crystallization of human language and culture and play an important role in human communication. The idiomatic meaning is not simply the sum of the lexical meanings, but often the metaphorical meaning extended from the literal meaning. The paper is based on the relevance theory proposed by Sperber and Wilson (1995), adopts the methods of comparative analysis and text analysis, and takes the idioms of “body metaphor” contained in English and Chinese as the main research object to explore the following questions: 1. What is the interpretation model of the “body-part metaphors” in idioms? 2. In English and Chinese idioms, what are the similarities and differences in the use and interpretation of body-part metaphors? Firstly, the idioms of body-part metaphor are classified based on their projection types, then analyzing the projection methods of each type. Finally, through the new reasoning model guided by relevance theory to analyze the reasoning process of body-part metaphor in English and Chinese idioms, exploring the importance of cognitive context in the interpretation of body-part idioms.


I. INTRODUCTION
Cognitive pragmatics, which emerged in the 1980s, is a subject that explains the use of speech in dynamic contexts based on the perspective of cognition. Pragmatics is related to cognition in both theoretical construction and practical analysis. It is necessary to reveal the output and understanding in verbal communication from the cognitive aspect. Sperber and Wilson (1995) have pointed out that pragmatics cannot be separated from the cognitive basis. Human's verbal communication can not be explained by a simple codes-decoding model. And the interpretation of discourse requires the communicator to truly understand the communicative intention behind the discourse with the help of reasoning in a specific context.
As a special way of language coding and language phenomenon, metaphor is an important form of the use of human language in communication. The early discussion on metaphor can be traced back to Aristotle, whose relevant theories have exerted such a profound influence that metaphor has long been regarded as a means of rhetoric and an important topic of rhetoric. In the 20th century, with the "linguistic turn" of Western philosophy, semantics aimed at exploring the meaning of language came into being. However, semantics cannot give a reasonable and satisfactory explanation of the meaning of metaphorical language in actual use, because the theoretical orientation of semantics isolated the use of metaphor from the context. To solve this problem, a pragmatic turn has taken place in the field of philosophy. That is, to study the use of language in a dynamic context. Compared with semantics, pragmatics has more explanatory power for the phenomenon of metaphorical language. In daily language communication, in order to realize communication activities, information receivers or listeners must decode and construe the language forms represented by metaphorical means according to the context if they want to recognize and understand the speaker's metaphorical utterance intention. But why does the listener or reader recognize and understand the metaphorical expression? This involves the cognitive perspective, so it is necessary to study metaphor in cognitive pragmatics.
In 1980, Lakoff and Johnson published Metaphors we Live By, which brought the study of metaphor into the cognitive stage. However, the study on the use of metaphor from a cognitive perspective only considers metaphor as a way for people to perceive and understand the world. It focuses on the mapping from the target domain to the source domain. Therefore, from the cognitive perspective of metaphor construction, although people can recognize and understand metaphorical discourse in a static state, they cannot analyze the real intention behind it. In 1986, Sperber and Wilson put forward a theory that deals with the relevance of communication and cognition, namely relevance theory. Relevance theory holds that the process of verbal communication is a process of expression and reasoning, and the key to successful communication is whether the speaker and the listener can find the optimal correlation. This theory can effectively explain the metaphorical phenomenon in language. The understanding of metaphor is the process of searching for similarity and, in essence, the process of searching for its optimal relevance. Relevance theory takes metaphor as ordinary discourse, which provides a new perspective for the interpretation of metaphor. In 2012, Wilson and Carston made a new interpretation of metaphor within the framework of relevance theory, which incorporated various pragmatic phenomena into a unified paradigm of lexical pragmatics based on ad hoc concepts. In other words, to understand metaphor, the listener needs to expand or narrow the coding concepts, then constructing ad hoc concepts. The ad hoc concept construction strengthens the analysis of metaphor under relevance theory.
Idioms are the crystallization of human language and culture. They are ubiquitous in language and play an important role in human communication. For English learners, whether they can use idioms fluently is often regarded as one of the important standards to measure their authentic degree of foreign language. However, idioms and their recognition in context are often the weak of learners' learning. The idiomatic meaning is not a simple sum of the lexical meaning, but a metaphorical meaning derived from the literal meaning. The expressiveness of idioms lies in the accurate transmission of their deep metaphorical meaning. According to the theory of "body experience", the body organ is an important way for humans to experience and understand the world, and it is the basis of conceptualization and cognition. The metaphor of human body has also become an important way for human beings to form and express abstract concepts. As human organs, their metaphorization will also effectively reflect the way that human form and express concepts. Therefore, studying body-part metaphors in idioms and their cognitive interpretation in context is of great significance to the success of communication.
First of all, this paper collects 423 English idioms and 312 Chinese idioms related to body parts from authoritative dictionaries and corpus. The Chinese dictionaries are Xinhua Idiom Dictionary (2013), The Great Chinese Dictionary (2010), Modern Chinese Dictionary (2016), and the English dictionaries include a Dictionary of Contemporary English Idiom (2000), Collins English Dictionary(2018), The Oxford English Dictionary(1989). The paper will analyze each idiom to explore its metaphorical meaning. Secondly, combining different social and cultural contexts, the paper will analyze English and Chinese texts that including these idioms. The texts are drawn from two corpora: CCL (Center For Chinese Linguistics PKU, http://ccl.pku.edu.cn:8080/ccl_corpus/) and COCA (Corpus of Contemporary American English, https://corpus.byu.edu/coca/). The linguistic data of the two corpora cover a wide range, such as newspaper, literature, translation, spoken language, historical biography, online language and so on. This paper has certain theoretical and practical significance. On the theoretical level, constructing the interpretation model of metaphorical cognitive discourse in human idioms under the guidance of relevance, and then deepening the cognitive-pragmatic research. The powerful explanatory power of relevance theory on metaphorical discourse is further strengthened, and the research scope of relevance theory is expanded. At the application level, it is hoped that the analysis of the understanding mechanism of human metaphor in idioms can help people better understand metaphorical idioms in discourse, provide a reference for second language acquisition learners to learn idioms, and also provide some help for the interpretation of Chinese and Western cultures.

II. LITERATURE REVIEW
Most foreign researchers study body metaphors from the cultural, semantic and cognitive aspects. Landa (1996) compares body metaphors between English and Spanish, exploring the semantic features of body spatial metaphors. Ning Yu (2000) compared the metaphorical usage of "finger" and "palm" between English and Chinese. Mette Kansa (2002) compared the mapping problems of body metaphors between Thai and English.
There is also much research on this topic going on in China in past years, especially focusing on cognitive metaphors. Chen Shuting (2020) discussed the relationship between conceptual metaphor and culture by comparing the body metaphor between Chinese and English. Wang Tiemei (2020) compared and analyzed body metaphors between English and Chinese based on the body words of bone, blood, tongue and so on.
There are numerous achievements about body idioms both aboard and home, and they are studied from different perspectives. But rare researchers analyze the body idioms from the cognitive and pragmatic perspective. Under the guidance of cognitive pragmatics, the purpose of the paper is to analyze idiomatic pragmatic inference of human organs in English and Chinese, from the perspective of relevance-theory.

A. Conceptual Metaphor
The Conceptual Metaphor Theory was put forward by Lakoff and Johnson in 1980, has become an important theory in cognitive linguistics. Lakoff (1993) claimed systematically the theory in his article Contemporary metaphor theory. The theory points out Metaphor is a systematic mapping from a specific conceptual domain to an abstract one. In cognitive linguistics, "domain" is a cognitive context for characterizing a semantic unit or concept. The theory is related to not language expression but the way of thinking.
The concrete conceptual domain refers to the source domain, such as the words about buildings. The abstract conceptual domain is called the target domain, such as theories. As the following examples: a. We need to buttress the theory with a solid argument. b. The foundation of the theory is shaky. C. The argument collapsed.
In these examples, Lakoff thought "buttress, foundation, shaky, collapsed" was used originally for describing the 838 JOURNAL OF LANGUAGE TEACHING AND RESEARCH building, but now used to describe theories. Therefore, theories are regarded as buildings, that is THEORIES ARE BUILDINGS. Lakoff suggested that a concept like this is common in human conceptual systems, and metaphor is a question of conceptual level. Thus he called metaphor as Conceptual Metaphor. Metaphor is a problem at the conceptual level, so he calls it conceptual metaphor. The core content of conceptual metaphor theory can be summarized into the following eight aspects. (l) Metaphor is a cognitive means "Metaphor is the main mechanism we use to understand abstract concepts and make abstract inferences." "Metaphors allow us to understand things that are relatively abstract or lack of internal structure in terms of more concrete, highly organized things." (2) The essence of metaphor is conceptual "Metaphor is fundamentally conceptual, not linguistic." "Metaphorical language is a surface manifestation of metaphorical thinking." Therefore, Lakoff called it conceptual metaphor.
(3) Metaphor is a systematic mapping across conceptual domains "Metaphor is a mapping across conceptual domains." "The mapping is asymmetric, it's partial." "Each mapping is a fixed set of ontological correspondences between the entities of the source domain and the target domain." Once those fixed correspondences are activated, the mapping can project the inference patterns in the source domain onto those in the target domain. Therefore, conceptual metaphors are cross-domain mappings.
(4) Mapping follows the constant principle "Metaphor mapping follows the principle of constancy: the image schema structure of the source domain is projected to the target domain through a manner of consistent with the internal structure of the target domain." Therefore, conceptual metaphor is the unidirectional effect of the source domain for the target domain.
(5) The basis of mapping is the experience of the human body "Mapping is not arbitrary, it is rooted in the human body, in the everyday experience and knowledge." This is also the important reason why Lakoff put conceptual metaphor theory in the field of cognitive linguistics.
(6) The essence of the conceptual system is metaphorical "Conceptual systems contain thousands of conventional metaphorical mapping, the conceptual system comprised of these mappings has highly organized subsystem." Therefore, conceptual metaphor is an integral part of the conceptual system and an important part of our knowledge system. (7) The use of conceptual metaphor is subconscious Most conventional conceptual metaphor systems are unconscious, automatic and effortless, just like our language system and the rest of our conceptual system. (8) Conceptual metaphor is common to all human beings The universality of metaphor mapping is special; some seem to be universal, others are widespread, and still others seem to be sort of culture-specific.

B. Relevance Theory
1. Relevance The Relevance Theory was put forward by Dan Sperber and Deidre Wilson in their book "Relevance: Communication and Cognition". The theory aims to describe and explain communication behavior from the cognitive perspective and explore the general principles of human cognition and communication. Relevance Theory explores the internal mechanism of communication from the perspective of cognition, involving many disciplines such as philosophy of language, psycholinguistics, cognitive science and pragmatics.
Relevance theory is a relatively important and new theory in linguistics, which tries to solve philosophical problems related to human communication and explain cognitive problems in the process of understanding discourse (Wilson, 2000). Levinson (1989) once reviewed the theory as bold and controversial because "the author attempts to shift the focus of pragmatic study from the usage to cognition". Relevance theory opens up a new field for pragmatic research and provides a new theoretical perspective for cognitive psychology. Using relevance theory, we can make a convincing explanation of the mechanism and characteristics of human mental activities, so as to reveal the internal rationale of human brain activities (Chen Xinren, 1998). Relevance theory has entered the mature stage, showing strong explanatory power in the fields of pragmatics, rhetoric, communication, cognitive psychology and philosophy of language (Sperber &Wilson, 1998), especially for figurative language, this theory can be regarded as a promising theoretical framework to explain the effects of figurative language (Gibbs & Tendale, 2006).
Relevance theory is based on the principle of relevance. Relevance theory is a part of the basic theories of cognitive pragmatics, which involves cognition and communication. The main reason why both parties can communicate smoothly and understand the implication of each other's words lies in a cognitive model of seeking relevance. By finding the optimal correlation through the discourse and the contextual assumption, communicators can infer the contextual implication in accordance with the optimal contextual assumption and obtain the contextual effects, thus achieving successful communication and achieving communicative goals.
2. Cognitive principle and the communicative principle of relevance The definition can also be explained that: under the same conditions, if the influence exerted by the cognitive effects was much stronger, the optimal relevance of the information input in communication would be attained; under the same JOURNAL OF LANGUAGE TEACHING AND RESEARCH 839 conditions if the processing effort made by communicators was much less, the optimal relevance of the information input in communication would also be attained. Based on this definition, we define relevance as a process of inputting a vast amount of information into the human cognitive mechanism. In general, it is analyzed in accordance with the definitions of cognitive effect and processing effort. (Clark,2012). When an utterance is generated in a specific context, in which some available assumptions would arise, the speaker modifies and recognizes these assumptions at the same time; and then the utterance may produce some cognitive effects. So-called contextual effect and processing effort serve as two central factors influencing relevance.

C. The Metaphorical Interpretation Based on Relevance Theory
For metaphor, the common cognition is to use one concrete thing to understand another one, which is also the interpretation of metaphor under conceptual metaphor. However, metaphor involves metaphorical intention, which needs to be explored by combining it with pragmatics. Relevance theory shows its extensive power to explain metaphor.
Relevance theory distinguishes the explicit meaning from the implicit meaning that is derived from the explicit meaning. The listener or reader needs to make a series of contextual assumptions based on the known knowledge and contextual information and finally deduce the implied conclusion. Carston (2012) makes a new interpretation of metaphor. They believe that to understand metaphorical discourse, it is necessary to make appropriate adjustments to the concept of metaphorical words, to construct corresponding ad hoc concepts, which will expand or shrink the original concept. That is to say, the listener or reader needs to retrieve relevant encyclopedic knowledge in the cognitive context, and then make a series of assumptions, according to the principle of optimal relevance, combined with the current context, select the most relevant hypothesis, to construct the ad hoc concept of this metaphor. The ad hoc concept may be the extension or contraction of the semantic scope of the encoding concept, or it may not coincide with the semantics of the encoding concept. The relevance theory uses the ad hoc concept constructions to explain metaphor. The expanded or narrowed temporary concepts are only the result of cognitive processing. The new interpretation does not give a detailed explanation of the immediate processing process when people understand metaphor. In addition, psycholinguistic experiments show that people do not need to use the literal meaning to understand the meaning of metaphor, nor do they compare whether two concepts are enlarged or narrowed. Therefore, the "ad hoc concept" is just a theoretical analysis tool for linguists, and cannot show the real process of metaphor understanding of communicators.
According to the above analysis, this paper constructs the discourse interpretation model of body-part metaphor in idioms under relevance theory, the express information--contextual assumption--ad hoc construction--understanding discourse. That is to say, through the express information coding the content of concept, content. According to the logical information, encyclopedic knowledge, word information, listeners or readers can make contextual assumptions. And then combining with the cognitive context to adjust the coding concepts, thus making an understanding for metaphorical expressions.

IV. THE ANALYSIS AND DISCUSSION
Lu Weizhong (2003) divided metaphorical projection of body parts into the projection from the human body domain to the non-human body domain, including the concrete domain and abstract domain. Projection from non-human domain to the human domain, including color domain，spatial domain, number domain and other non-human domains. The final is the projection between two body parts. Besides these types, it is common that the relation of two body parts project to the relation of matters. This paper will classify the collected English and Chinese idioms according to the classification. Wang Caili (2002) divided the metaphorical projection methods of the human body into three types, which are based on position, structure and function. But some metaphorical projections are found making projections through emotional cognition and Conventional knowledge. The paper will analyze the main projection modes of each type of idiom. Then some metaphorical idioms are selected to analyze their interpretation patterns in context.

A. The Conceptual Metaphor of Body-part Idioms in English and Chinese
Whether in English or Chinese, the projections from the body-part domain to the concrete domain are mainly based on position and structure projection. The human conceptual domain was first used to refer to specific objects or something similar. The head of a mountain, the waist of a mountain and the foot of a mountain in English, and "山头", "山腰" and "山脚" in Chinese, all use the head, waist and foot to name the top, middle and bottom of mountains. Although English and Chinese are different, people understand and recognize the external features of other things in the same way. That is, metaphorized human body makes the understanding between different languages possible. However, it is difficult for many other expressions, such as a tongue of land, a finger of land, a slip of the tongue, an arm of the sea, to be found in Chinese. This shows that English takes the sea as its target domain, while Chinese takes mountains as its target domain. This is because the natural and geographical environment has a profound influence on the formation of metaphorical thinking. Many parts of China are inland and China is a country with many mountains. The Chinese language almost uses all different body parts to represent the different positions and shapes of mountains. Britain is an island country surrounded by the sea, and its navigation industry once took the lead in history. Since ancient times, The British people have been fond of sailing, and they know the world, explore the world and carry out territorial expansion using sailing. They have deep feelings for the sea, so they observe the sea very carefully.

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In English and Chinese idioms, there are also a large number of projections based on similar functions, such as the heart of a story in English. In Chinese, bed leg, table leg, etc. This kind of metaphor is relatively easy to understand because of the great similarity in everyone perceives their bodies. However, in the projection from the human body domain to the abstract domain, in addition to the projection based on the similarity of shape, structure and function, many expressions rely on human organs to realize emotional cognition. The most commonly used body parts are "eyes" and "heart". As emotional animals, human beings often express their rich inner feelings with the help of their eyes. Different eyes express different feelings and inner feelings. For example, when people are angry, they tend to open their eyes wide, and when they are in love, they often have tender eyes. Therefore, both English and Chinese use "eye" to express "emotion", such as "cast sheep's eyes", "make eyes at someone" in English, and "媚眼," "飞眼," "眉来眼去" in Chinese. However, people from different cultural backgrounds observe and understand things from different perspectives. Therefore, there are subtle differences between Chinese and English in expressing emotions with the help of body metaphors. For example, when facing the emotional fact of anger, Chinese people may have "大动肝火", "七 窍生烟". But in English, they use ears, like someone is pouring out of his ears. English has the conceptual metaphor of eyes move in joy. In Chinese, the conceptual metaphor of joy is not only reflected in the movement of the eyes, but also the eyebrows. Such as "眉开眼笑", "舒美展眼", "喜眉笑眼". In Chinese, eyebrows are also important tools to express inner activities, such as "眉来眼去", "眉目传情", "愁眉苦脸" and so on.
Many non-human domains, including spatial domain and color domain, are projected into the human domain to achieve metaphorical expression. Cognitive linguistics holds that spatial metaphors play a particularly important role in the formation and expression of human concepts. Most abstract concepts are understood and expressed through spatial metaphors (Lan Chun, 1999). In Chinese, "heart" can be regarded as three levels of spatial concepts. They are one-dimensional space, two-dimensional space and three-dimensional space. In one dimensional space, "heart" is regarded as a straight line, the expressions include "一条心", "寸心", "细心", "心路", "心弦", "语重心长" and so on. In two-dimensional space, "heart" is regarded as a plat, such as "一片心", "心叶", "心地", "心田", "心坎", "心 潮", "心海" and so on. In three-dimensional space, "heart" is regarded as space, such as "心房", "心窝", "心窍" and so on. In contrast, the spatial metaphorical forms of "heart" are relatively rare in English, such as with a light heart, with a heavy heart, with half a heart, pull one's leg, etc. Color is an important cognitive object and category for human beings. After people get familiar with and grasp the basic types and characteristics of color, they then project it to the cognition and expression of other things. Among them, the human body word is one of the important projection targets of color words. Different languages give the color its cultural meaning, such as "黑心", "黑手", "红心", "赤心", "赤 胆忠心" in Chinese. The most representative are the names of facial makeup in Peking Opera, such as "白脸" symbolizes the villain, "红脸" refers to the positive figure, and "黑脸" refers to the upright figure. In English, there are blue-beard, red neck, green fingers and so on.
Metaphorical cognition of body parts is also reflected in the projection between two conceptual domains of the human body, focusing on the similarity of position, structure and function. One of the two body parts is the central word and serves as the target domain. The other is the modifier, which acts as the source domain. However, this type of projection is mostly seen in Chinese, such as "心眼", "唇齿相依", "唇枪舌剑", "头重脚轻", "赤胆忠心", "心口如 一" and so on, but this kind of projection is seldom seen in English.
In general, the body-part domain project into a specific domain is relatively easy to understand, because they are mostly based on the projection of position. After all, every nation has similar cognition for the position of body parts. However, for some projections based on function, emotional cognition and conventional knowledge, different nationalities have different cognitive focus, which requires a certain social-cultural background as a foundation. Therefore, it is important for people to use relevance theory to understand the body-part metaphor in English and Chinese idioms.

B. The Pragmatic Reasoning of Body-part Idioms in English and Chinese
Driven by relevance, relevance theory holds that the process of verbal communication is an explicit-inferential process. The main reason why both parties of communication can recognize and understand the explicit and implied content of the other party's discourse and cooperate well in communication is that there is an optimal cognitive model of relevance. This theory can effectively explain the metaphorical phenomenon in language. Relevance theory takes metaphor as ordinary discourse and explains its relevance, which provides a new perspective for the interpretation of metaphor.
In 2012, Carston made a new interpretation of metaphor within the framework of relevance theory, which incorporated various pragmatic phenomena into a unified paradigm of lexical pragmatics based on ad hoc concepts. In other words, to understand metaphor, the listener needs to construct corresponding ad hoc concepts by expanding or contracting the coding concepts. The construction of the ad hoc concept strengthens the analysis of metaphor under relevance theory. Constructing the interpretation model of metaphorical discourse based on the ostensive-inferential model of relevance theory. The model can be shown as: expressing information--supposing context--constructing ad hoc concept--understanding discourse. That is to say, through expressing information coding concept, according to the logical information, encyclopedic knowledge, word information making contextual assumptions. Then combining

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with the situation to extend or narrow concept, constructing the ad hoc concepts, thus understanding the expression. It is feasible to analyze the interpretation and reasoning process of human metaphorical idioms with linguistic data. The examples in context are as follows: Example one: Janet was like a bear with a sore head when she found out she had missed her connecting flight. In this example, the speaker uses the idiom like a bear with a sore head. The communicator may have the following contextual assumptions: (1) The speaker is making an assertion.
(2) There is a person named Janet.
(3) Janet is like a bear with a headache.
(4) Headaches can make people irritable and in a bad mood. (5) Janet has a flight to catch. (6) Janet showed a certain negative emotion when she knew she had missed her flight. Based on the encoded conceptual content "like a bear with a sore head", the listener concludes the semantic meaning, that is "Janet is like a bear with a headache", which does not satisfy the listener's expectation of relevance. Because it can not determine the truth-value of the corresponding proposition, and can not help complete the interpretation of discourse. To meet the associated expectation, according to 4) and 6), the contextual assumption that was obtained from the encyclopedic knowledge and context, the hearer or reader knows Janet has close contact with some negative effects. Guided by the principles of optimal relevance, the hearer selects contextual assumptions to handle coding concepts, and then constructing the ad hoc concept "like a bear with a terrible temper." Example two: 先是爸爸声严厉色的一顿教育批评，把孩子吼的直抹眼泪，也不敢哭出声。一看孩子眼泪也流 了，肯定有所思有所悟吧！也别太极端了，毕竟怕孩子太小受不了，这时候妈妈再上前抚慰，面对这颗巴掌后 的强塞的糖，孩子从恐惧不安的情绪里抽离，慢慢平静下来。夫妇二人都觉得这种"一个唱红脸一个唱白脸"的 方法很"平衡"，家里既有一个能唬住孩子的人，也有一个能照顾孩子情绪的人。 In this example, there is the idiom "一个唱红脸一个唱白脸", which means "one plays the role of a red face and one plays the role of a white face in the Peking Opera stage". According to express information, encyclopedic knowledge and situational information, the reader will assume the following cognitive context: (1) The author is an adult.
(3) This idiom involves in two people, one with a red face and one with a white face.
(4) Red face and white face have opposite meanings. (5) Father is a good cop, the mother is a bad cop. (6) A person is strict and another person is gentle.
The red face looks strict, while the white face looks mild. Similarly, only according to the coding concept "一个唱红脸一个唱白脸," concluding the context 3). It is difficult to know its implied meaning. So to satisfy the relevant expectation, the reader considers encyclopedic knowledge and contacts situational context information, extracting 4) 5) 6), to know that there are near contact, between "红脸" and "strict", "白脸" and "mild". Thus the reader enriches the content of the encoded concept, constructing the ad hoc concepts of red face and black face. That is, one plays a strict role, the other plays a mild role. Then the interpretation is completed. This expression is related to the art of facial makeup in Chinese drama. The red face symbolizes loyalty, courage and determination, while the white face symbolizes evil and sinister. "Red face" is thus promoted to refer to positive characters, while "white face" symbolizes treacherous villains. According to the similarity of the roles, they are projected into family life to realize its overall metaphorical meaning "in life, one person plays a positive role and the other person plays a negative role". In the metaphorization of human words, the meaning of the new words is far from the literal meaning, presenting a rich and colorful cultural symbolic meaning.
Provided that one cannot understand the culture behind idioms, according to conceptual metaphor, it is difficult to understand the idioms. Thus the metaphorical interpretation model guided by relevance theory is required to help communicators complete the reasoning of idioms.

V. CONCLUSION
Whether in English or Chinese, the projections from the body-part domain to the concrete domain are mainly based on position and structure projection. This is because people have similar cognition for their body structures. For the projections from body-part domain to abstract domain, most projections are based on the similarities of function. English and Chinese have different focus of body-part functions, so they may intend to use different body parts to project the same abstract domain. For instance, English uses the eye to express joy, while Chinese also uses eyebrows to express joy. To express anger, English uses ears, while Chinese uses liver.
Many non-human domains, including spatial domain and color domain, are projected into the human domain to achieve metaphorical expression. In addition to the projections based on function, most of them are projected through emotional cognition and conventional knowledge. In Chinese, "heart" can be regarded as three levels of spatial concepts. They are one-dimensional space, two-dimensional space and three-dimensional space. However, the spatial metaphorical forms of "heart" are relatively rare in English. Both English and Chinese project color domain into body-part domain, but they have different cognitions for the characteristics of color. Thus they give color their cultural meaning. Metaphorical cognition of body parts is also reflected in the projection between two conceptual domains of the human body, focusing on the similarity of position, structure and function. However, this type of projection is mostly seen in Chinese, and they are seldom seen in English.
Every language has its deep cultural background and historical origins. Idioms are the crystallization of human language and culture. They are ubiquitous in language and play an important role in human communication. Idioms have their particular cultural connotation, which makes them difficult to be understood. Thus due to cultural differences, there is a certain limitation to interpret idioms through conceptual metaphor. The new model based on the ostensive-inferential model has given a full explanation of the interpretation process of the metaphor in body-part idioms in both English and Chinese. Therefore, it is necessary for people to use relevance theory to understand the body-part metaphor in English and Chinese idioms. Although the reasoning model cannot fully eliminate the cultural differences in idioms, it can mitigate the differences.
When the hearer notices the metaphorical expressions in idioms, the hearer is certain to search in the encyclopedic knowledge to build contextual assumptions and try to distinguish the resemblances between the two to infer the implicatures carried by the metaphorical expressions and then constructing the ad hoc concepts. Within the framework of relevance theory, the paper finds that metaphors can be employed as an ostensive stimulus at the same time earring implicated information for the hearer to achieve the optimal relevance as the metaphorical expressions in body-part idioms have expected. As an ostensive stimulus, metaphor can attract the hearer's attention in hopes of guiding him or her to achieve optimal relevance. Then he or she is encouraged to see the resemblance between the two thus helping to understand the metaphorical meaning of the idioms.
However, there are still some limitations. First, there are some limitations in data collection indeed. Restricted by time and energy, the paper only chooses a small number of representative examples of body-part idioms in both English and Chinese, so these data are not perfect and adequate. Second, because of the choice of the corpus, it was found that some idioms did not find corresponding frequency and examples in the process of sorting the corpus. Thus, a more comprehensive language resource and knowledge are needed in the process of future research.