1　Introduction

This study introduces the dual functions of English abstracts as core carriers of academic communication, notes that previous research has focused predominantly on superficial features such as rhetorical structure and metadiscourse while neglecting the cognitive dimension, and subsequently proposes to adopt an encoding-decoding dual-process perspective, using information entropy and dependency distance as measurement indicators to examine the diachronic evolution of cognitive difficulty in English abstracts of Chinese and international applied linguistics journals from 2000 to 2024.

2　Literature Review

This section traces the development of research on cognitive difficulty in academic abstracts: early studies relied on readability formulas to analyze superficial features, later shifting to linguistic features such as lexical and syntactic complexity, yet still lacking systematic evaluation frameworks. The advancement of quantitative linguistics has promoted the application of two types of cognitive indicators based on working memory load (e.g., dependency distance) and surprisal (e.g., information entropy), with the former measuring reader decoding difficulty and the latter reflecting author encoding difficulty. Existing research has predominantly focused on the decoding dimension, with insufficient attention to encoding difficulty, and lacks diachronic tracking and cross-cultural comparison. The dichotomous framework proposed by Zhao et al. (2023) provides theoretical foundation for integrating the dual-process perspective, yet still has limitations including static analysis and scarcity of intra-disciplinary Chinese-foreign comparisons.

3　Research Design

Research design for the diachronic study of cognitive difficulty in English abstracts of Chinese and international academic journals based on information entropy and dependency distance. The study addresses two core questions: what diachronic characteristics and differences are exhibited in cognitive encoding difficulty and cognitive decoding difficulty of abstracts in Chinese and international applied linguistics journals. The corpus comprises 250 English abstracts each from Applied Linguistics and Chinese Journal of Applied Linguistics from 2000 to 2024, constructing a comparable corpus. For measurement indicators, information entropy adopts the Miller-Madow correction algorithm to quantify text uncertainty reflecting cognitive encoding difficulty, while mean dependency distance is calculated through syntactic dependency relations to characterize cognitive decoding difficulty. Data processing employs R for entropy calculation, Stanford CoreNLP for syntactic analysis and MDD calculation, with final statistical analysis conducted through curve fitting, linear regression, independent samples t-test, and Granger causality test.

4　Results and Discussion

This study examines the diachronic changes in cognitive difficulty of English abstracts in Chinese and international applied linguistics journals from 2000 to 2024, conducting comparative analysis from two dimensions: cognitive encoding difficulty (information entropy) and cognitive decoding difficulty (mean dependency distance, MDD).

Regarding cognitive encoding difficulty, entropy values in both international journals (AL) and domestic journals (CJAL) show significant upward trends, with CJAL growing faster (β=0.011>0.007), though AL consistently maintains higher levels (M=6.641 vs. 6.446). The two demonstrate significant positive correlation (β=0.741, p=0.013), yet Granger causality tests reveal no "lead-lag" predictive relationship. This trend stems from continuous accumulation of disciplinary knowledge, theoretical paradigm innovations, and pressures of academic publication competition, leading to constantly increasing information density in abstracts. Notably, this finding contrasts with Zhao et al.'s (2023) conclusion regarding no significant change in cognitive encoding difficulty of humanities abstracts, highlighting the impact of analytical level differences on research conclusions—as an interdisciplinary field, applied linguistics exhibits far more rapid knowledge updating than traditional humanities disciplines.

Regarding cognitive decoding difficulty, AL's MDD values show a weak downward trend (β=-0.002, p=0.627), while CJAL shows an upward trend (β=0.007, p=0.104), with obvious differences in change rates and significant negative correlation between the two (β=-0.701, p=0.01), though again no Granger causal relationship exists. AL's stable pattern reflects the dual constraints of dependency distance minimization principles and mature genre conventions; CJAL's increase reflects domestic scholars' strategic use of promotional metadiscourse and complex nominalization structures to enhance academic visibility, with this "excessive imitation" of international academic discourse forms temporarily elevating cognitive processing load.

Synthesizing both indicators, international journal abstracts present a mature pattern of "high encoding difficulty—stable decoding difficulty," while domestic journals demonstrate transitional characteristics of "rapid encoding difficulty catch-up—fluctuating decoding difficulty increase." The absence of unidirectional causal influence between the two indicates that domestic journal development represents an autonomous evolutionary pathway driven by both intrinsic disciplinary demands and local evaluation systems, rather than simple following of international models.

5　Conclusion

This study summarizes the diachronic evolutionary characteristics of cognitive difficulty in English abstracts of Chinese and international applied linguistics journals from 2000 to 2024: cognitive encoding difficulty shows increasing trends in both domestic and international journals, with international journals consistently higher than domestic journals; cognitive decoding difficulty shows divergent patterns, with domestic journals increasing while international journals remain relatively stable. The study notes that higher encoding difficulty in international journals stems from emphasis on theoretical innovation and methodological diversity, while increasing decoding difficulty in domestic journals reflects their adaptation to international academic discourse norms. The study acknowledges limited sample coverage and recommends future expansion of corpus scale and observation time span.