1. Introduction

Introduced syntactic complexity as an important indicator for measuring second language proficiency, emphasizing the importance of micro syntactic complexity parameters in describing the relationship between syntactic structure and language proficiency. Existing research has mostly focused on written expression, with insufficient research on the micro syntactic complexity of oral expression texts and their relationship with oral proficiency. The aim of this study is to analyze the micro syntactic complexity indicators of different genres of oral texts, explore their predictive power on oral proficiency, and investigate the impact of genres on the composition of syntactic complexity dimensions.

2. Literature review

Reviewed the different indicators of syntactic complexity and their applications in language proficiency research. Macro and micro syntactic complexity indicators are distinguished, with macro indicators focusing on overall complexity and micro indicators reflecting specific syntactic structures. Research has shown that micro indicators can reflect learners' language production characteristics in more detail. Existing research has mostly focused on written texts, while there is relatively little research on the syntactic complexity characteristics of oral texts. There are differences in syntactic structure between oral dialogue and written expression, but there is still a lack of research on the micro syntactic complexity differences in different genres of oral expression. Empirical research plays an important role in understanding the relationship between text features and language proficiency, but there are limitations in research methods and genre selection. Biber et al. proposed a domain functional view of syntactic complexity, emphasizing the causal relationship between syntactic structure and communicative needs in specific contexts. This study explores the impact of genre on the syntactic complexity of oral expression among Chinese English learners and its predictive effect on oral proficiency, guided by the functional perspective of register.

3. Research Design

Introduced the research design, including corpus sources, sample selection, rater training, and consistency testing. Extract syntactic complexity indicators using TAASSC software, and process the indicators through data cleaning and collinearity analysis. Exploratory factor analysis was conducted using the R software package to screen for effective indicators. Using Bayesian multiple regression analysis to explore the relationship between syntactic complexity and oral proficiency, selecting the BRMS package to improve model prediction reliability, and handling ordinal variables.

4. Results and Discussion

The clustering relationship differences of micro syntactic complexity indicators between oral discourse and oral discussion texts of Chinese English learners were studied using factor analysis method. The study found that the micro syntactic complexity index of oral discourse texts is clustered on 13 factors, while oral discourse texts are clustered on 10 factors. There are differences in the complexity of passive voice, verb phrases, noun complements, conjunctions and structures, and conjunctions or structures between the two genres. The complexity of modifiers such as qualifiers, prepositional objects, passive voice, verb phrases, and nouns in oral discourse texts can significantly predict learners' oral proficiency. In oral discussion texts, the complexity of direct object, prepositional object, prepositional quantity, and possessive case can significantly predict learners' oral proficiency. The syntactic complexity characteristics that distinguish learners of different levels vary among different genres of spoken texts.

5. Conclusion

Through factor analysis and Bayesian multiple regression methods, the differences in syntactic complexity between oral discourse and oral discussion among Chinese English learners were studied. Research has found that the syntactic features of oral discourse are similar to those of argumentative essays, while oral discourse is distinguished by prepositional phrases. With the improvement of language proficiency, learners begin to have a sense of style, and syntactic features gradually shift towards oral expression. In oral teaching, learners' awareness of language style should be cultivated, and language structures with different communicative functions should be taught. Exam task design should encourage learners to use more formal complement clauses and adverbial clauses to approach real-world communication tasks.