1 Introduction

This section introduces the importance of interpretation in cross-cultural communication, points out that interpreted language possesses unique linguistic features, and highlights that the explicitation of the optional complementizer "that" is one of the research hotspots. Existing studies mostly focus on comparisons between professional interpreters’ interpreted language and native speakers’ natural spoken language, while systematic empirical comparative research on the explicitation of "that" and its cognitive mechanisms in Chinese learners’ interpreted language versus natural spoken language remains limited. Based on a balanced corpus and adopting functional and cognitive perspectives, this paper analyzes the distribution characteristics of "that" explicitation and omission following seven types of reporting verbs, aiming to fill the research gap, enrich the theory of interpreted language as a variant, and provide references for interpretation teaching and interlanguage theory development.

2 Research Background

First, this section outlines the development of explicitation in translation studies, from early theoretical foundations to modern typological classifications and interdisciplinary research, emphasizing the importance of explicitation theory in translation studies. Next, it focuses on explicitation in interpretation, exploring differences in explicitation patterns between simultaneous and consecutive interpreting and their influencing factors. Additionally, it discusses the use of the optional complementizer "that" in translation and interpretation, as well as learners' characteristics and tendencies when using "that," providing a theoretical basis and research direction for subsequent studies.

3 Research Methodology

This chapter elaborates on the research methodology, including the theoretical framework, methodological framework, and data selection and analysis. The theoretical framework is based on genre theory and interlanguage theory, treating interpreted language as an independent language variant and learners’ interpreted language as a form of interlanguage. The methodological framework employs corpus linguistics, analyzing large-scale text or speech samples to identify linguistic features across different corpora. Data selection encompasses learners’ interpreted language, professional interpreters’ interpreted language, learners’ second-language spoken language, and native speakers’ spoken language, with diverse and representative sources. Research tools include NLTK, WordSmith Tools 8.0, and Python 3.9, used for part-of-speech tagging, basic statistics, and specific analyses. Data analysis focuses on the frequency of "that" and its zero form following seven reporting verbs, aiming to reveal "that" explicitation across different corpora.

4 Research Findings

Through comparative corpus research, this chapter analyzes the use of the optional complementizer "that" and its zero form following reporting verbs in Chinese learners’ interpreted language, professional interpreters’ interpreted language, learners’ second-language spoken language, and native speakers’ spoken language. The findings indicate that the frequency of "that" in interpreted texts is significantly higher than in natural spoken language. There is no significant difference in "that" usage between learners’ interpreted language and professional interpreters’ interpreted language, but both differ significantly from natural spoken language. Furthermore, usage patterns of "that" and zero complementizers following different verb types vary. Following objective verbs, the PI corpus shows the highest frequency of "that" usage; following subjective verbs, the LI corpus shows the highest frequency; and following verbs with both objective and subjective properties, the LI corpus also exhibits the highest frequency.

5 Discussion

This section discusses differences in the use of the complementizer "that" across different corpora. It points out that the explicitation rate of "that" in both learners’ interpreted language and professional interpreters’ interpreted language is generally higher than in natural spoken language, which is attributed to the high-pressure and immediate nature of interpretation tasks leading interpreters to rely more on structurally explicit expressions. Learners’ interpreted language shows a strong tendency toward explicitation across all verb types, while professional interpreters’ usage patterns are closer to those of native speakers, reflecting their stronger language regulation ability and stylistic adaptability. Learners’ natural spoken language has the lowest explicitation rate with mixed-type verbs but is higher than native speakers’ natural spoken language with subjective verbs, displaying transitional characteristics of interlanguage. Interpreters exhibit a conservative tendency in omitting "that," opting for omission only in specific contexts, possibly due to cautious self-assessment of language ability and considerations to reduce the risk of communication misunderstandings. Additionally, factors such as ambiguity avoidance, fluency of language production, and cognitive complexity also influence "that" usage. The study also notes that interpreted language, as a form of "interlanguage," possesses a unique linguistic system more influenced by task objectives and communicative strategies, showing significant differences from natural spoken language.

6 Conclusion

This chapter summarizes the research findings based on four monolingual unidirectional corpora, revealing that both interpretation learners and professional interpreters exhibit significantly higher explicitation characteristics of "that" in Chinese-to-English interpretation compared to second-language learners and native speakers’ spoken language, confirming the independence and explicitation tendency of interpreted language as a style. It also analyzes interpretation learners’ reliance on explicit linguistic markers under high cognitive load, providing insights for interpretation teaching, including targeted training and enhancement of metacognitive awareness. Additionally, it points out research limitations, such as single sample sources, insufficient quantity and diversity of corpora, and the need for further validation of the generalizability of conclusions, and proposes future research directions, including expanding samples, diversifying data types, and strengthening collaboration with professional institutions.