Ethical approval
The study protocol was approved by the Ethics Committee of Guangzhou Vocational University of Science and Technology (approval number 2026120130404). All participants provided informed consent before enrollment and were informed that they could withdraw without academic consequence.
Study design
This study employed a quasi-experimental, two-group, three-time-point mixed-methods design to examine immediate and delayed between-group trajectory differences associated with VP-CGWIP in EFL learners' writing performance and critical thinking disposition. Learner perceptions of usefulness, ease of use, and behavioral intention (BI) were assessed descriptively in the experimental group at T1 rather than treated as intervention outcomes. The design followed a quantitatively driven, qualitatively embedded logic (QUAN(qual)): quantitative data formed the primary evidentiary chain for estimating group-by-time differences, while qualitative data were embedded throughout the intervention to illuminate the cognitive and behavioral processes accompanying those differences. The two strands were integrated at the interpretive stage through a joint display12. Because one intact class represented each condition, class membership and instructional condition could not be statistically separated; accordingly, all between-group findings were interpreted as exploratory associations rather than definitive causal effects.
A quasi-experimental rather than a fully randomized design was adopted because the writing course was organized around two pre-existing intact classes and no student-level randomization was conducted. One intact class received VP-CGWIP and the other served as the control condition. Baseline comparisons were used to describe the comparability of the final analytic sample, but were not treated as proof of equivalence or as a means of eliminating class-level confounding. Three measurement points were established: a baseline pretest (T0, one week before the intervention), an immediate posttest (T1, during the final week of the ten-week intervention), and a delayed posttest (T2, four weeks after the intervention concluded). The control condition was matched to the experimental condition in AI access, writing-task load, and scheduled instructional hours. Because VP-CGWIP combined protocol visualization, structured Accept/Modify/Reject judgment, critical dialogue, adoption-log recording, and reflective activity, the between-group contrast estimated the association with the combined intervention rather than the isolated contribution of any single component.
The software, instruments, platforms, and study-specific materials used in this protocol are summarized in the Table of Materials.
Preregistration and analysis status
The study was not prospectively preregistered. The outcome hierarchy and multiplicity correction were specified retrospectively. All inferential analyses are exploratory.
Participants and sampling
From January to April 2026, participants were recruited from two intact classes of second-year university students who were not English majors enrolled in an EFL writing course at Guangzhou Vocational University of Science and Technology, Guangzhou, Guangdong, China. One class received VP-CGWIP and the other received the control instruction; no student-level randomization occurred. Eligibility required a College English Test Band 4 (CET-4) score of at least 425 and no previous systematic training in structured AI-assisted writing. Observed completer CET-4 scores ranged from 449 to 532. Each class initially included 50 students. Seven experimental and eight control participants were excluded for attendance or delayed-assessment reasons, leaving 43 and 42 participants, respectively; 15 of 100 participants (15.0%) were excluded. Figure 2 summarizes exclusions for missing at least two sessions (experimental, 4; control, 5) or not completing T2 (3 in each class). The complete-case sample contributed outcomes at T0, T1, and T2. Baseline tests concern completers only. Additional descriptive baseline summaries for the excluded students are reported in the Results; these summaries do not rule out selective attrition.
The VP-CGWIP intervention
The experimental class received the ten-week VP-CGWIP intervention shown in Figure 1. During weeks 1–2, the instructor presented the seven-step cycle and introduced prompt construction and checks of factual accuracy, logical consistency, and rhetorical appropriateness. During weeks 3–8, students submitted independently written drafts to ChatGPT, recorded individual suggestions in an AI Feedback Adoption Log, and classified each suggestion as Accept, Modify, or Reject with a written reason. Classroom dialogue addressed disagreements with AI feedback. During weeks 9–10, students continued judgment and logging activities and combined self-assessment, teacher feedback, and log entries in final revisions. Reflective journals followed the six elements of Gibbs' cycle: description, feelings, evaluation, analysis, conclusion, and action plan13. Students accessed ChatGPT through the official OpenAI web interface (chatgpt.com) using ChatGPT Plus accounts. Browsing, file-upload, and other auxiliary tool functions were disabled during the instructional activities. No temperature or other model-generation parameters were manually specified; the platform-default settings were retained.
Operational sequence and fidelity
Use an independent plan and first draft as the inputs to the cycle. For each AI suggestion, compare the proposal with the intended meaning, relevant language evidence, and the task requirements before assigning Accept, Modify, or Reject. Record the suggestion, the decision, the reason, and any resulting revision in the log; retain a reason for non-adoption. Discuss unresolved or competing judgments in class and revisit them during revision and reflection.
Control group design
The control class completed the same writing tasks and scheduled instructional hours, had access to ChatGPT, and received conventional teacher feedback. The experimental class additionally used the visualized cycle, structured judgment, and adoption logs, critical dialogue, and reflection activities. The same instructor taught both classes. Each class had two 90 min sessions per week for ten weeks, corresponding to 20 sessions and 30 scheduled instructional hours. The amount of teacher feedback and the actual time on task were not available for comparison. Equal scheduled hours do not establish equal instructional intensity. The contrast concerns the integrated package, and additional attention or practice may partly account for the observed class difference.
Study procedure and timeline
The intervention and follow-up covered 14 weeks: ten intervention weeks followed by four weeks without further intervention input. Baseline assessment (T0) occurred one week before the intervention; the interval from baseline to T2 was therefore approximately 15 weeks. T0 included timed writing, CTDI-CV, and background information. At T1 (intervention week 10), both classes completed writing, CTDI-CV, and the AI-feedback judgment task; only the experimental class completed the Technology Acceptance Model (TAM) questionnaire. At T2 (week 14), both classes repeated writing, CTDI-CV, and the judgment task to examine four-week maintenance. No baseline judgment task was administered. Adoption logs covered weeks 3–10, and reflective journals covered weeks 9–10. Figure 2 distinguishes the assessment schedule from participant flow.
Outcome measures and instruments
Table 1 summarizes the outcomes and measurement occasions. Overall writing score is the main outcome emphasized in this report; the four writing dimensions and the remaining outcomes are secondary or exploratory. Two IELTS-certified raters, blinded to group assignment, used the Task 2 dimensions Task Response (TR), Coherence and Cohesion (CC), Lexical Resource (LR), and Grammatical Range and Accuracy (GRA). The IELTS Task 2 band descriptors specify these four criteria14; published work on AI-assisted accuracy assessment provides additional context15. The administered CTDI-CV comprised 70 items, with ten items per dimension and a six-point response scale (1–6). It assessed seven self-reported disposition dimensions: truth-seeking, open-mindedness, analyticity, systematicity, critical-thinking self-confidence, inquisitiveness, and cognitive maturity. The feedback judgment task sampled responses to valid suggestions and deliberately flawed or contextually inappropriate suggestions at T1 and T2. It is treated as task-specific performance, not a validated general measure of critical thinking. The experimental-class adoption logs and journals describe classroom processes. At T1, an adapted TAM questionnaire measured perceived usefulness (PU), perceived ease of use (PEOU), and BI in the experimental class16. The TAM instrument contained 15 items rated on a five-point scale (1–5): six PU items, six PEOU items, and three BI items.
Data collection procedures
Writing assessments lasted 40 min and were completed in a classroom without AI assistance. Different prompts were used at T0, T1, and T2. Overall writing score was the arithmetic mean of the four criterion scores. Electronic questionnaires recorded response durations, and logs and journals were submitted through a writing platform. Process summaries concern the 43 experimental-class completers. Limitations of prompt comparability and measurement reliability are considered in the discussion.
Judgment task development
The judgment task comprised 20 items: ten trap-feedback items and ten valid-feedback items. Parallel forms were used at T1 and T2. Three EFL instructors reviewed the task, and it was piloted with 20 students who were excluded from the main study. Judgment scores are expressed as percentages. The task measures performance on the selected feedback items.
Quantitative analysis
All statistical analyses were conducted in R. The complete-case analysis included 85 participants and 255 repeated observations. A unique group-plus-participant identifier linked observations across time. Gaussian linear mixed-effects models were fitted using lme417, with inferential tests implemented using lmerTest18: outcome ~ group * time + (1 | uid), where group and time are categorical, Ctrl and T0 are the reference levels, and uid uniquely identifies each participant. Restricted maximum likelihood (REML), Satterthwaite denominator degrees of freedom, independent constant-variance residuals, and participant random intercepts were used. This structure implies compound-symmetric marginal covariance. The two interaction coefficients quantify experimental-minus-control differences in change from T0 to T1 and T0 to T2; pointwise 95% t intervals are reported. All 13 outcome models converged without singular fits. A sensitivity analysis added grand-mean-centered CET-4 as a fixed covariate. Continuous baseline comparisons and judgment comparisons used two-sided Welch t tests; sex counts used Pearson’s chi-square test without continuity correction. Judgment Cohen’s d used pooled sample SD. TAM associations used Pearson correlations with T1-minus-T0 overall writing change and Fisher z CIs. Aggregate baseline characteristics of excluded participants were summarized descriptively. No missing-data imputation or individual-level attrition sensitivity analysis was performed. Participant-level models cannot separate the effects of class and condition.
Multiple testing
Post hoc Holm adjustment was applied to 18 nominal p values: five writing interactions, eight CTDI-CV interactions, two judgment comparisons, and three TAM correlations19. Baseline tests and CET-4 sensitivity models were not included in this family. Pointwise contrast and correlation intervals were not adjusted for multiplicity; adjusted omnibus p values do not test a particular T1 contrast. All analyses are exploratory.
Qualitative analysis and integration strategy
The analysis in NVivo 20 followed Braun and Clarke's thematic-analysis framework20. Codes combined deductive categories from TAM, CTDI-CV, and content, process, and premise reflection with inductive categories arising from the logs and journals. Two coders worked independently, with disagreements resolved through discussion. All qualitative summaries concern the 43 experimental-class completers. The joint display places aggregate qualitative descriptions alongside quantitative results as contextual complements. Individual-level convergence and causal mechanisms were not tested; limitations of coding reliability and case selection are considered in the Discussion.