This study addresses the gap in research on the combined effects of multiple factors on language output in xu-argument based continuation writing tasks. While previous research has explored individual factors like genre and input enhancement, their combined impact and interaction remain under-examined. Complexity, accuracy, and fluency (CAF) are established measures of L2 writing proficiency, reflecting the learner's ability to use sophisticated structures and vocabulary, produce error-free language, and write smoothly, respectively. The xu-argument based continuation writing task, requiring learners to creatively and logically continue an incomplete text, has shown promise in enhancing language learning, due to its alignment effect. This study investigates the impact of input enhancement (visual highlighting of language forms) and genre (narrative vs. argumentative) on CAF in continuation writing tasks, aiming to understand how these factors individually and interactively influence learner performance. The researchers hypothesize that both input enhancement and genre will influence CAF, and an interaction between these two factors is expected, particularly in accuracy.

The literature review examines existing research on CAF in L2 writing and the continuation writing task, input enhancement techniques, and genre effects on writing. Studies show CAF as a comprehensive measure of L2 writing proficiency, allowing for a more nuanced assessment than focusing on individual aspects of writing. The continuation writing task has received attention for its ability to couple language input and output, promoting language learning through alignment. However, most previous studies have focused on single factors influencing the task's effectiveness. Regarding input enhancement, research shows its effectiveness in drawing learner attention to specific language forms, leading to improved learning outcomes. Genre, as a type of discourse with specific communicative purposes and linguistic features, has been shown to significantly impact writing performance. However, studies exploring the interaction between input enhancement and genre in continuation writing are lacking. This gap necessitates the current study's investigation into the combined effects of these two factors on learners' writing performance.

This study employed a two-factor mixed experimental design with 80 Chinese high school EFL learners. Participants were randomly assigned to either an enhanced group (with highlighted language forms in the input text) or a non-enhanced group. Both groups completed two continuation writing tasks: one narrative and one argumentative. The length of the incomplete texts was controlled, and the topics were relevant to the participants' daily lives. The enhanced group received input texts with 24 language features (vocabulary, lexical blocks, and syntactic structures) highlighted via underlines. Participants wrote approximately 150 words for each continuation. The data collection involved collecting and analyzing the written compositions. Data from participants completing both tasks were analyzed. To ensure balanced group sizes, the number of participants were standardized to 40 in each group. The learners' writing performance was assessed using seven CAF indices: Uber index (lexical diversity), Lambda value (lexical sophistication), C/S (clauses/sentences – general syntactic complexity), CN/T (complex nominals/T-units – phrasal complexity), 1-LE/CW (lexical accuracy), EFT/T (Error-free T-units – syntactic accuracy), and W/T (words per T-unit – fluency). Statistical analysis using SPSS 24.0, particularly repeated measures in the general linear model and simple effect tests, were employed to examine the main effects and interactions of input enhancement and genre on each CAF index.

The study found that genre significantly impacted all three aspects of CAF (complexity, accuracy, and fluency). Narrative continuations showed greater lexical diversity, while argumentative continuations exhibited higher lexical sophistication and fluency. Input enhancement significantly improved lexical accuracy, but not complexity or fluency. There was a significant interaction effect between input enhancement and genre on lexical and syntactic accuracy. Simple effect tests revealed that input enhancement did not significantly affect the lexical accuracy of narrative continuations, but significantly improved the lexical accuracy of argumentative continuations. In terms of syntactic accuracy, the enhanced argumentative continuations were more accurate than the enhanced narrative ones, while no significant difference was observed between the non-enhanced continuations. The interaction effect was not significant for complexity or fluency. Figures (not included in this summary) visually represent the means plots of the different CAF measures, illustrating the differences between enhanced and non-enhanced groups across the two genres.

The findings partially support the hypotheses. While both input enhancement and genre had significant effects on CAF, their interaction was only significant for accuracy. The lack of effect of input enhancement on complexity and fluency may be due to the limited number of enhanced language forms or learners' tendency to avoid using complex forms they haven't fully mastered. The genre differences in CAF align with prior research indicating that different genres demand distinct linguistic features. The interaction effect suggests that the effectiveness of input enhancement varies across genres. Input enhancement was more effective in improving accuracy for argumentative texts, possibly because argumentative writing requires more precise use of language structures. This suggests the need for careful selection of materials and structures to be highlighted for the continuation task, aligning with the learners' zone of proximal development. The results also highlight the importance of considering genre when designing language learning tasks. The study's findings have implications for the development of effective continuation writing tasks, emphasizing the need to consider the interplay between input features, genre characteristics, and learner proficiency.

This study demonstrates that genre significantly influences complexity, accuracy, and fluency in continuation writing tasks, while input enhancement primarily affects accuracy. The interaction between input enhancement and genre is prominent in accuracy. These findings suggest that effective continuation writing tasks should carefully select appropriate genres and highlighted structures tailored to learners' current language abilities and learning goals. Future research could explore a wider range of genres and input enhancement techniques, conduct longitudinal studies to track long-term effects, and investigate the underlying cognitive processes involved in continuation writing. The limitations of the current study, including the limited sample size and the restriction to two genres, should be addressed in future studies.

The study's limitations include a relatively small sample size (80 students) and the inclusion of only two genres (narrative and argumentative). The short-term nature of the study may not reflect long-term effects. The specific type and number of language features highlighted may have also influenced the results. The reliance on self-reported data might introduce bias. The study also did not directly measure learner attention to the highlighted language features. These limitations might affect the generalizability of the findings to other contexts or learner populations.