Research On Neuro-mechanism Of Chinese Metaphorical Cognition

With the development of human society to the twenty-first century, man has learned a great deal of the natural world around him by resorting to the power of science and technology. However, man knows little about his own brain and its function on which he depends to understand and explore the natural world. It is said that the twenty-first century should be an era of cognition, an era of brain science. Indeed, talking about cognition without the mental function of the brain is equal to talking about the universe without heavenly bodies. The chief mental function of the brain is thinking, which involves language, logic, calculation, analysis, music, fine arts, imagination, creation and so on. Metaphorical thinking is an important way of thinking with language, whose process ought to be run under the framework of the cognition in the brain. Metaphor is a way of thinking as well as a form of language. Therefore, metaphorical thinking has its unique forms, characteristics and functions.The study for metaphors has a long history. However, such study was once restricted within the field of rhetoric research over a long period. Since the 1980s, the foreign researchers have successively put forward a series of theories concerning metaphorical cognition, and thus expanded its scope from linguistics into the whole cognitive science whose purpose is to reveal the law of man's thinking. Meanwhile, the rapid advance of the means of neuroscience enables us to observe the neuro-mechanism of language cognition on line via electrophysiological methods. Recently, resorting to the constantly updated techniques of neural imaging and analysis, some western scholars have attempted to explore the neuro-mechanism of metaphorical cognition by means of ERP (Event-related Potential) and fMRI (functional Magnetic Resonance Imaging) in order to profoundly probe into the conventional issue of the relationship between language and thought. Following their steps, the author has also tried to do the research on metaphorical cognition by means of electrophysiology. But different from them, this research has focused on Chinese metaphorical cognition via ERP experiment. Therefore, the ERP experiment has been conducted with some Chinese metaphors and control literal sentences. 20 native Chinese undergraduates majoring science as subjects were asked to perform the experiment. Their behavioral data and ERP data were recorded on line and analyzed off line. The results have been discussed to offer the explanation for the unique dynamic neuro-mechanism of the Chinese metaphorical cognition. On the basis of the existing theories of metaphorical cognition and from the perspective of brain information processing, the dissertation tries to verify metaphorical cognitive theories by ERP experimental results and to do research on Chinese metaphorical cognition in the framework of the linguistic cognition of the brain. The main contributions are as follows:1. A new model is developed to offer more reasonable explanation for metaphorical cognition. Concerning metaphorical cognition models, the most classical ones are the Two-Step Processing Model (TSPM) insisted by Searle and his followers, and the One-Step Processing Model (OSPM) advanced by Lakoff & Johnson. Although from the synchronic point of view the two models are reasonable to some degree, i.e. at a certain phase of the development and cognition, the metaphor processing can be explained by one of the models (at the beginning phase the novel metaphor can be processed according to Searle's TSPM while at its conceptualized phase the process of the dead metaphor can be accounted for by Lakoff &Johnson's OSPM), it is believed by the author that from diachronic perspective a metaphor from its creation to its conceptualization is by nature an evolutionary course from novel metaphor to dead metaphor. Accordingly, metaphorical cognition is a developmental course from two-step processing to one-step processing, i.e. a course of the agent's familiarity with the metaphor. Such transitional point of view has in effect theoretically developed for the interpretation of metaphorical cognition. 2. A hypothesis is advanced that association is the mapping mechanism for metaphor comprehension. The understanding of a metaphor is a process of understanding a particular meaning beyond the lines, which involves the mapping between the two different domains. It is put forward in the dissertation that association is the means for this sort of psychological mapping. It is not only because association is the psychological basis for metaphorical cognition, but also because the semantic connection of association has its own neural network basis for information connection. In metaphorical cognition, the important function of association lies in the matching between the input of literal meaning and its psychological schema so as to output the metaphorical meaning instead of literal meaning. The processing of a novel metaphor begins with the processing of its literal meaning. When the agent cannot find its matching model from the literal meaning in his/her original neuron connection, he/she will ward off the routine to match with a relevant alternative with a novel meaning, which is determined by the plasticity of the brain. But as far as the dead metaphor is concerned, even if it is in a mess, it will be processed by means of its habitual neural cluster binding, i.e. by means of association to conduct the matching between the literal meaning and its metaphorical prototype as long as a portion is detected in the neural network.3. The agent's controlling function is emphasized in the comprehension of metaphors. Metaphorical cognition is affected by quite a few factors which may be divided into agentive factors and contextual factors. In the dissertation, special emphasis is put on the effect of agentive factors, including the agent's familiarity with the metaphor, his/her age and his/her educational background. It is firmly believed by the author that agentive factors play a dominant and decisive role in linguistic cognition because the agent can only understand the underlined meaning of a metaphor which is of course different from the literal meaning on the surface when he/she has the capability of metaphorical cognition. If he/she lacks the ability to comprehend a language as a foreigner or a baby or if he/she has lost such ability as an aphasic, the certain metaphor would mean nothing to him/her. In that case, it's unnecessary at all for us to talk about the context even though the context is most relevant to the metaphor because it is just like whistling jigs to a milestone. Therefore, the process of metaphorical cognition is sure to start from the agent, from the extent of his/her familiarity with the metaphor.4. A breakthrough is achieved to the research method for Chinese metaphorical cognition. If a theory is put forward to persuade others, it should be verified by the practice even if it is a good theory. Since the agent plays such an important role in the process of metaphorical cognition, we are sure to find some clues of metaphor processing in the brain information processing. On the one hand, although some foreign researchers have taken a lead to observe the mechanisms of metaphor in its generation, understanding and processing areas in the brain from the perspective of brain mechanism, there are few of them do such research on Chinese metaphors. On the other hand, quite a few Chinese scholars are doing research on Chinese metaphorical cognition, but practically no one up till now has done his/her research resorting to ERP experiment. Learning from their experience, the author has adopted the EEG cortical imaging technique to conduct an ERP experiment on the understanding of Chinese metaphors with selected Chinese metaphors as corpus. In this way, a breakthrough is achieved to the research method for Chinese metaphorical cognition.5. The current theories are verified in the study for metaphorical cognition and the brain processing of metaphors. It is found from the results of the ERP experiment that there do exist some differences between metaphorical processing and literal processing. On the basis of the analysis and discussion, some reasonable conclusions are made: (1) It is proved by the electrical activities corresponding to the metaphor comprehension from the brain imaging that metaphorical cognition, like other sorts of cognition with flesh basis, does have its related neural activities in the brain and must be processed within the neural network; (2) Judging from the corresponding brain waves at the frontal lobe on both hemispheres in the course of metaphor comprehension, the process of metaphorical cognition involves both language areas on the left side and some cortical cognitive models relevant to the content of certain metaphor, especially those for imagery processing on the right side, from which it is deducted that in the neural network the connection of clusters of neurons links the metaphorical processing on both sides, likewise, association in mind makes possible the mapping between different conceptional domains; (3) Metaphorical cognition is impacted by its agent and his/her ability to understand the metaphor, which is verified by the findings that the time course of metaphorical cognition in ERP is directly affected by the agent's familiarity with the sentence and that the agent's familiarity with a certain metaphor has directly affected his/her way of processing it; (4) It is indicated by the behavioral data and ERP data that the processing of metaphorical meaning is more difficult than that of literal meaning in Chinese, and that there are significant differences at 250～350ms (N400) and 750～900ms (LPC) of the frontal electrodes between the two different types of processing, showing that it is harder for the agent to process metaphorical meaning than to process a literal meaning since the agent made more efforts for and pay more attention to a metaphor with the same sentence patterns; (5) In the course of Chinese semantic processing, the slightly earlier N400 latency has something to do with the difference between languages as well as experimental objectives, from which it is concluded that to some degree Chinese metaphorical processing has its uniqueness.Nevertheless, it does not necessarily follow that we can make a definite conclusion just by one experiment. The above conclusions and predictions need to be verified or proved by more experiments and from other different perspectives. Anyhow, this is the first time in our country that brain imaging technique has been adopted to do research on the neuro-mechanism of metaphorical cognition. Although the road is rough, the future is bright.