1. Introduction

Modifiers play a crucial role in linguistic expression, enriching sentence structure and semantics, and serve as an important indicator for measuring the complexity of language production. However, due to their flexible usage and lack of strict grammatical constraints, learners often encounter difficulties when employing modifiers. Interlanguage theory treats learner language as a unique and research-worthy linguistic variant, where the interlanguage forms produced by learners from different native language backgrounds contribute to exploring language acquisition mechanisms and transfer phenomena. The morphological differences between Chinese and German may pose challenges for Chinese students in learning German modifiers. Hirschmann's research indicates that Chinese learners of German underperform in adverb usage frequency, yet there is a lack of specialized studies on Chinese learners' modifier usage in German. Therefore, it is necessary to investigate the dynamic developmental trends and characteristics of their modifier usage.

2. Theoretical Basis and Literature Review

Interlanguage theory is a core concept in second language acquisition, describing the dynamic natural language system that learners gradually approximate to the target language during their developmental process. This theory emphasizes three main characteristics of interlanguage: systematicity, permeability, and dynamism, distinguishing it from both the learner's native language and the target language. As a form of linguistic expression, modifiers are not constrained by higher-order grammatical systems and can be single words or phrases, with complex classifications. This study adopts the Stuttgart-Tübingen Tagset (STTS) for part-of-speech categorization, selecting six types of modifiers for analysis: ADJA, ADJD, ADV, PAV, PRELS/PRELAT, and PTKNEG. Chinese scholars have conducted in-depth research on modifier usage among foreign language learners, often employing comparative methods and identifying discrepancies between learners and native speakers. However, studies on modifier usage among German L2 learners remain limited, with issues such as narrow research scope and a lack of long-term dynamic developmental investigations. Based on interlanguage theory, this study examines argumentative essays by Chinese learners of German, focusing on modifier frequency and diversity as analytical dimensions across different academic years, aiming to provide empirical evidence for the dynamic developmental mechanisms of learners' interlanguage competence.

3. Research Design

This chapter, grounded in interlanguage theory, selects 120 learner texts from the Chinese German Learner Corpus (CDLK) to explore changes in modifier frequency and diversity in argumentative writing. The study addresses two research questions: 1) modifier usage frequency, and 2) trends in modifier diversity. The corpus comprises texts from German majors at five Chinese universities, covering four learning stages to ensure authenticity and independence. Native German speakers' modifier usage serves as a reference, with argumentative texts from the Falko corpus used for comparison. Data processing employs UTF-8 encoding, preserving learners' original expressions, while EXMARaLDA software and the STTS annotation system are used for part-of-speech tagging. Relative modifier frequencies are calculated to account for corpus size differences, and CTTR values quantify modifier diversity, excluding relative pronouns and negators.

4. Results and Analysis

A detailed analysis of Chinese German learners' modifier usage development in argumentative writing is presented. The findings reveal a nonlinear trend in modifier frequency, initially decreasing, then increasing, and finally decreasing again, with the highest frequency observed at Stufe 3, though still lower than that of native speakers. The most frequently used modifier type is adverbs, followed by adjectives, while pronominal adverbs and negators are less common. Modifier diversity improves with learning progression but remains significantly lower than that of native speakers. Specifically, the developmental trends in attributive and adverbial adjective diversity align with overall modifier diversity, whereas adverb-type modifiers exhibit lower CTTR values and more frequent repetition. Pronominal adverbs show even lower CTTR values, likely due to their grammatical properties. Learners prioritize using pronominal adverbs to clarify causal relationships between clauses, enhancing logical coherence in their writing. Overall, the developmental dynamics of modifier usage do not follow a uniform universal pattern but rather constitute a dynamically evolving, multi-dimensional interplay.

5. Conclusion

Based on interlanguage theory, this study analyzes the development of modifier usage in argumentative writing by Chinese learners of German. The findings indicate gaps between learners and native speakers in both frequency and diversity, with modifier frequency peaking in the third year of university before declining. Adverb-type modifiers are the most frequently used. Modifier diversity improves with learning duration, but development varies across modifier types. Learners tend to favor simpler vocabulary while emphasizing causal relationships between sentences. Teachers should prioritize modifier instruction, strengthen writing skill training, and analyze synonymous modifier distinctions to enhance precision. Future research could expand corpus size and conduct longitudinal studies to provide deeper pedagogical insights.