| The construction and change of scientific concepts is one of the main aims of scientific education.Divergent,convergent,associative and transfer thinking adopted in learning scientific concepts all involve the cognitive processing of scientific metaphors.Adopting scientific metaphors to manipulate the cognitive process is a basic mechanism of constructing and transforming scientific concepts,which is a fundamental micro-process of scientific education.Over the past years of scientific educational practice,many outstanding scientists and educators have accumulated successful experiences of flexible and effective using of scientific and daily metaphors.With the rapid development of scientific technology,with the combination of psychology,biology,neurocognition and linguistics,the comprehensive study of the neurocognitive mechanism of scientific metaphors has become an interdisciplinary study trend in the field of scientific education,whose findings might be methodologically and epistemologically significant to scientific educational practice.With its high temporal resolution of millisecond and multi-dimensional component analysis,event-related potential(ERP)has become an ideal tool to study the implicit,continuous and complicated cognitive processing of metaphors.By adopting the ERP study paradigm of conventional metaphors and poetic metaphors,the current study compared the elicited degree and area of the brain for scientific metaphors with those for conventional metaphors and poetic metaphors as well as those for scientific language and those for conventional literals,thus observing the neurocognitive mechanism of scientific metaphor.Scientific metaphors are used in the scientific context,which warrants their unique contextual structure and analogical function.Firstly,the contextual structure of scientific metaphors is more complicated with the two domains covering scientific and daily contexts,which the N400 of ERP is very sensitive to.Secondly,in the later period of the cognitive processing of scientific metaphors,there is a reasoning process from the concrete source to the abstract target leading to the sudden understanding of the knowledge,which the late components of ERP are very sensitive to.Accordingly,the current study designed three ERP experiments to study the neurocognitive mechanism of scientific metaphors step by step.In experiment 1,scientific metaphors and conventional metaphors were comparatively studied to test whether the mechanism for scientific metaphors is different from that for conventional metaphors due to its unique metaphoricity,familiarity and abstractness,thus laying an important foundation for the following experiments.Adopting the end-word paradigm,ERPs were time-locked to the onset of the last word of the sentence and were obtained by stimulus-locked averaging of the EEG recorded in each condition.Epochs were 1000 ms long with a 200 ms pre-stimulus baseline.There were three categories of sentences:scientific metaphoric,conventional metaphoric and daily literal.Three pilot surveys were conducted to rate the meaningfulness,figurativeness and familiarity of the stimuli.The results indicated that metaphoric sentences elicited more negative N400 that literal sentences,with scientific metaphors eliciting the most negative one especially in the right hemisphere.Following the N400,both scientific metaphors and conventional metaphors elicited the late negativity with scientific metaphors having more negative one similarly in the left and right hemispheres.Because of the late negativity overlapping the time window of the LPC,the amplitudes of the LPC for metaphoric sentences appeared lower than that for literal sentences.The findings of experiment 1 show that the difficulty for processing metaphors is bigger than that for literals and that for scientific metaphors is even bigger.Besides,due to the reasoning process to have the sudden understanding of the knowledge,the reintegration of the meaning for scientific metaphors continues to be difficult during the later period of processing.Based on the findings of experiment 1,in experiment 2,scientific metaphors were further compared with another new kind of metaphors,poetic metaphors.Although both of these two kinds of metaphors are novel ones,scientific metaphors have its unique contextual structure and knowledge-understanding function.So,the results of experiment 2 could focus more closely on the effect of scientificity on the processing mechanism of metaphors.The experiment paradigm and data processing methods were similar to those of experiment 1.There were four categories of sentences:scientific metaphoric,poetic metaphoric,conventional metaphoric and daily literal.That is to say,poetic metaphors were added into the stimuli.The rating of the concreteness of the last words of all the experimental sentences was done except for the other three ratings similar to those in experiment 1.The results indicated that because both were novel,there were no significant differences between the N400 for scientific metaphors and poetic metaphors.Following the N400,both these two kinds of novel metaphors elicited the late negativity,with scientific metaphors having more negative amplitude both in the left and right hemispheres.More importantly,in order to observe clearly the differences of processing these two kinds of novel metaphors,the LPC time window was further divided into three subwindows.The results indicated that as time passed by,the differences between the amplitudes of scientific metaphors and poetic metaphors became more and more significant,and compared to poetic metaphors,processing scientific metaphors involved larger and larger areas of the brain.It seems that under the influence of the abstract scientific metaphors,poetic metaphors become more and more conventionalized,which makes its processing easier even approaching the level of conventional metaphors.Finally,based on the findings of experiments 1 and 2,in experiment 3,scientific language was compared with conventional language.The experiment paradigm and data processing methods were similar to those of experiments 1 and 2.There were three categories of sentences:scientific metaphoric,scientific literal and daily literal.The ratings for the pretests were similar to those in experiment 1.The aim of the present study is to further investigate the neural mechanism of scientific language by observing the differences between scientific language(metaphoric and literal)and daily expressions as well as between scientific metaphors and literal expressions(scientific and daily).The results indicated that scientific language(metaphoric and literal)elicited more negative N400 than daily literal sentences with scientific metaphors having the most negative N400 both in the left and right hemisphere.The unique complicatedness and abstractness of scientific metaphors reduce its meaning saliency,thus increasing the difficulty of processing.From the perspective of conceptual metaphors,using the study methods of cognitive neurology and linguistics,the current study compared the neural processing mechamism of scientific metaphors with that of poetic metaphors and conventional metaphors,and compared the neural processing mechanism of scientific language(metaphoric and literal)with that of daily literals.The current study comes to the following conclusions:firstly,the more complicated contextual structure of scientific metaphors results in the longer distance between the source and target domains,requiring more efforts to establish the mapping;secondly,the more exquisite reasoning process of scientific metaphors makes the further integration of the two domains more difficult,leading to the more difficult and longer comparison process;thirdly,both the left and right hemispheres are involved in the processing of scientific metaphors,but comparatively speaking,the right hemisphere,especially the right-parietal area,is important for scientific thinking.These findings might basically show the neural mechamisn of scientific cognition when learners try to construct and transform their scientific concepts.More significantly,based on the fingdings of the neural processing mechanism of scientific metaphors,some suggestions have been given for scientific concept teaching,such as successive using conventional metaphors and scientific metaphors,choosing suitable ways to develop scientific thinking according to leaners'conditions and emphasizing learners' reading ability in scientific classroom.In this way,some insightful perspecitves might be put forward to further deepen and optimize scientific concept learning to provide some theoretical framework for the design and application of more applicable scientific teaching methods. |
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