| Research articles are important carriers to promote information dissemination and function as a vane of academic frontiers,and the research article abstract serves as an important part of research articles to summarize research findings and to reveal the significance of pertinent research.Due to the particularity of this genre,research article abstracts become the focus of discourse analysis and have received extensive attention in recent years.Previous research on abstracts primarily focused on the rhetorical structure such as move analysis,and language features encompassing complex nouns and syntactic complexity.These studies have revealed the structural and linguistic features of research article abstracts,while few of them have examined this genre from the perspective of cognitive aspects.Besides,pertinent studies mainly focused on the synchronic dimension while few were concerned with diachronic changes of this genre.To bridge the abovementioned research gaps,this study introduces cognitive encoding and cognitive decoding difficulty indices to the theoretical foundation of text difficulty calculation,hence revealing the changes in the text difficulty of research article abstracts diachronically from the perspective of cognitive encoding and decoding difficulty.Based on 1890 high-level research article abstracts extracted from the Web of Science,the present study explored the diachronic changes in the text difficulty of research article abstracts from 2000 to 2020.Two quantitative indices encompassing entropy and dependency distances were adopted to reveal diachronic changes in cognitive encoding difficulty and cognitive decoding difficulty of research article abstracts respectively.Simple linear regression was conducted to check whether diachronic changes in cognitive encoding difficulty and cognitive decoding difficulty were significant and whether different communities demonstrated cross-disciplinary differences.The present study obtained the following results.(1)Concerning the cognitive encoding difficulty,the overall entropy values of research article abstracts showed a steady upward trend.The cognitive encoding difficulty of research article abstracts in the natural sciences and social sciences showed a significant increase,and that in the humanities was comparatively stable over these years.(2)Concerning the cognitive decoding difficulty,it was found that the overall dependency distance of research article abstracts showed a significant downward trend.The cognitive decoding difficulty of research article abstracts in the natural sciences and humanities showing a significant declining trend,while that in the social sciences was comparatively stable.Since academic research and academic information are continually accumulated,the accumulating nature of research fruits makes the recent academic studies more complicated than previous ones,hence the cognitive encoding difficulty of academic texts shows an increasing trend.However,due to the limited working memory of human beings and the purpose to promote research,authors tend to intentionally construct academic texts with less cognitive decoding burden,hence the cognitive decoding difficulty of academic texts shows a decreasing trend.Different disciplines show diverging diachronic features concerning cognitive encoding and decoding difficulty across disciplines,which might be explained by the fact that they have divergent ontologies,methodologies,and epistemologies.This study provides a new index for the measurement of text difficulty by introducing entropy and dependency distance.Moreover,the present study reveals the dynamic development of abstracts,and hopes to deepen the academic community’s understanding of the diachronic changes in research article abstracts.Lastly,the present study hopes to help teachers and students understand the diachronic changes in academic discourse and disciplinary differences,which has implications for the pedagogical practice of academic writing in related fields. |
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