Topic and Vehicle Play Different Roles in Processing of Metaphor: Activation and Inhibition of Semantic Features of Constituent Terms

Topic and Vehicle Play Different Roles in Processing of Metaphor: Activation and Inhibition of Semantic Features of Constituent Terms Keiko Nakamoto (kenakamoto@nifty.com) Takashi Kusumi (kusumi@educ.kyoto-u.ac.jp) Graduate School of Education, Kyoto University. Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501, Japan Among many models of metaphors (e.g., Lakoff & Johnson, 1980; Kintsch, 2000), two major psychological models focus on the asymmetric roles of a topic and a vehicle in comprehension process—the alignment model (Gentner, 1983; Gentner & Wolff, 1997; Wolff & Gentner, 2000) and the class inclusion model (Glucksberg, 2003; Glucksberg & Keysar, 1990). The alignment model assumes that in a nominal metaphor the topic and vehicle terms denote literal concepts, and metaphor processing begins with a bidirectional comparison between the two, and predicts that the two terms are equally processed in the early phase of comprehension. In contrast, the class inclusion model claims that the roles of the topic and vehicle differ even in the initial phase. This model assumes that the vehicle term of a metaphor has dual functions— referring to the conventional literal referent, and denoting the more abstract, metaphoric category. According to this model, we must inhibit the literal meanings of a vehicle and make an appropriate abstraction of it in order to interpret a metaphor. More specifically, the class inclusion model states that the vehicle would first be processed to arrive at an interpretation. Although both these models have been evaluated using various psychological experiments, which of the models is more suitable for explaining the metaphor comprehension phenomena is still inconclusive. Some researches have demonstrated that both the topic and vehicle play an important role even in the earliest processing stage of metaphors (Gentner & Wolff, 1997; Wolff & Gentner, 2000), while other studies reported that the roles played by the topic and vehicle in metaphor comprehension differs from the commencement of processing (Gernsbacher et al., 2001; McGlone & Manfredi, 2001). On the basis of these findings, Glucksberg and his colleagues have proposed a model that has been modified from the original class inclusion model. The model, called the interactive property attribution model, assumes that the sentence structure of metaphors should be considered in order to explain the manner in which they are understood. Abstract This paper has examined the asymmetric roles of a topic and vehicle in the metaphor comprehension process. We began by proposing a perspective on the roles of topic and vehicle in terms of the sentence and discourse structure. According to this perspective, the topic, together with the preceding context, would convey information regarding the aspects of the topic that are relevant in creating a coherent interpretation of the metaphor with the entire discourse. In contrast, the vehicle would convey information regarding the types of objects or events it would represent. Thus, it is predicted that a prior presentation of a metaphor-relevant feature of the topic would facilitate the comprehension of the corresponding metaphor, while a metaphor-irrelevant feature of the vehicle would interfere with the comprehension. Two experiments were conducted in order to test these predictions, taking a priming paradigm similar to that of McGlone and Manfredi (2001). The obtained results were supportive of our proposal and suggested the importance of considering sentence and discourse structure to reveal the metaphor processing Key words: metaphor comprehension; priming effects; activation and inhibition of semantic features Introduction The purpose of this study is to explore the asymmetric roles of the topic and the vehicle in comprehending metaphors. The manner in which people comprehend nominal metaphors, such as “crime is a disease” is one of great interest in cognitive processes of natural language. In general, it is believed that metaphor interpretation is primarily based on the semantic features that the vehicle (disease) and the topic (crime) have in common (Gentner, 1983), or the features that the vehicle consists of, and are applicable to the topic (Glucksberg & Keysar, 1990). In this case, the features such as {harmful, spreading rapidly , . } would be used for the interpretation. However, the topic and vehicle have features that are irrelevant to the achieved interpretation. For example, most people would not consider that the metaphor intends to refer to the features of the topic such as to be punished or those of the vehicle such as causing a fever. Therefore, people must suppress or inhibit those features of the topic and the vehicle that are not relevant to metaphor interpretation; they must activate or focus on the metaphor-relevant features. With reference to this point, one related problem arises: would metaphor- irrelevant and relevant features be treated equally or differently for a topic and a vehicle? More specifically, are suppression and activation processes of topic and vehicle features similar or different? Reconsidering nominal metaphor comprehension in terms of a sentence and discourse structure In general, assertions would include given and new information (Clark & Haviland, 1977). For example, in the assertion “The first speaker of this session is my colleague,” the noun phrase the first speaker of this session would express information that is commonly shared by the speaker to the hearer (i.e., they know that there has been a talking session that has several speakers and that someone will give