Students Know What Plagiarism Is, Yet Half Still Cross the Line, Study Finds

Plagiarism has haunted universities for centuries, but a new study from Indonesia suggests that the real problem may not be dishonesty so much as a stubborn gap between what students know and what they actually do when they sit down to write. Researchers at the State University of Medan surveyed 105 undergraduates and scrutinized the actual writing assignments of 30 more, and the results paint a picture of a student body that can define plagiarism with surprising accuracy yet still fails, more often than not, to keep its own work below institutional similarity thresholds.

The study, published in the journal Discover Education, was led by Muhammad Takwin Machmud of the Department of Community Education, together with colleagues Nurhudayah Manjani and Natalia Silalahi. The team set out to answer a deceptively simple set of questions: how well do university students understand plagiarism, how often do they engage in plagiarism-related behaviors when completing assignments, how do they use plagiarism detection tools, and how do their similarity scores compare with the benchmarks their university imposes?

When asked to define plagiarism in their own words, 81 of the 105 surveyed students, or 78.6 percent, produced answers that matched the expected conceptual keywords, such as stealing or duplicating other people’s work, failing to credit the original author, or claiming someone else’s work as one’s own. On the surface, that sounds encouraging. But the researchers noted that most students framed plagiarism narrowly, as literal copy-pasting, while only a small minority described it in broader terms such as academic dishonesty or violations of intellectual ethics. The team also acknowledged a caveat: because the questionnaire was administered without supervision, some students may have looked up definitions online before answering, a limitation consistent with prior research showing that self-reported measures of academic integrity knowledge can be inflated by external assistance or socially desirable responses.

The behavioral data told a more complicated story. A majority of students, 61.9 percent, reported that they only occasionally paraphrase when adapting information from original sources, while 31.4 percent said they always paraphrase and just 6.7 percent said they never do. Direct copying was far more common than the researchers anticipated: 87.6 percent of students admitted to occasionally copying information directly from sources, and 5.7 percent said they always do. When students were interviewed about why, many explained that copying had become a routine time-management strategy, even though they still cited the original authors. The researchers interpreted this as evidence that many students simply struggle to paraphrase properly, hampered by heavy assignment loads, difficulty understanding dense reading materials, limited vocabulary, and, by their own admission, occasional laziness.

Citation practices, by contrast, appeared relatively healthy. More than half of the surveyed students, 58.1 percent, said they always credit the original author, 37.1 percent said they do so occasionally, and only 4.8 percent reported never citing sources. In other words, students are not wholesale thieves of ideas; they are writers who attribute their sources but often fail to transform them, reproducing sentence structures and phrasing so close to the original that detection software flags them anyway.

To move beyond self-reports, the researchers analyzed 30 scientific article assignments written for a Research Methodology course, running each document through university-approved plagiarism detection software under standard institutional settings that excluded bibliographies and quoted text and ignored small matches below one percent. The results were striking. Similarity index scores ranged from 5 percent to 85 percent, with an average of 41 percent and a median of 36.5 percent, and a standard deviation of roughly 22.5 percent indicating enormous variability in writing practices. Against the university’s benchmark, which caps similarity at 35 percent for undergraduate students in the social sciences and humanities, only 14 of the 30 assignments passed. Sixteen, or 53.3 percent, exceeded the threshold.

Perhaps the most technically revealing finding concerned where the matched text came from. Internet sources accounted for the largest share of similarity matches, averaging 39.7 percent, followed by previously submitted student papers at 18 percent and academic publications at just 12.4 percent. This pattern suggests that students lean heavily on open web resources when completing assignments, and that some flagged text may echo work already sitting in detection databases from earlier student submissions. The researchers connect this to broader concerns raised in the literature: the sheer abundance of online material and the ease of accessing it have been cited as key drivers of rising plagiarism, and reports from Indonesia indicate that student plagiarism cases climbed by nearly 70 percent in 2017 alone.

The study also examined how students actually use plagiarism detection tools, and here the findings were more optimistic. Turnitin dominated, used by 73.3 percent of surveyed students, well ahead of Grammarly at 36.2 percent, Duplichecker at 21 percent, Unichecker at 11.4 percent, and other tools at 8.8 percent. Students gravitated toward paid software, explaining that the university provided premium access and that paid platforms offer richer features: vast databases spanning journals, books, magazines, and webpages; detailed similarity reports identifying the original sources of matched text; highlighted passages of concern; and support for many document formats. Turnitin’s own database, according to figures cited in the study, contains 1.9 million student papers, 190 million subscription articles, content from 1,500 publishers worldwide, and coverage of 97 percent of the top 10,000 journals.

Crucially, the researchers found that detection tools function not merely as gatekeepers but as revision aids. Analyzing institutional records from 24 final-year social science students who defended their theses between January and June 2025, the team documented students running multiple checks to drive their scores down. One student cut a similarity index from 42 percent to 13 percent between the first and second checks; another dropped from 40 percent to 14 percent; a third ran three checks, gradually descending from 28 percent to 26 percent to 25 percent. Across all 24 theses, final similarity indices ranged from 5 percent to 31 percent, averaging 22.8 percent, a level most students achieved only after iterative revision. The software, in effect, had become part of the writing process itself, with 82.9 percent of surveyed students using it for scientific articles, 52.4 percent for academic reports, and 39 percent for daily assignments.

The authors caution that a similarity index is an indicator of textual overlap, not proof of misconduct, since properly cited quotations, references, and common academic phrases can inflate scores, and that thresholds vary widely across institutions and publishers, with no single universal standard. They also note challenges such as false positives and privacy concerns that universities must manage through clear policies and training. Still, their conclusion is pointed: plagiarism among university students should be treated not only as an ethical failing but as an academic literacy problem demanding pedagogical solutions, from explicit instruction in paraphrasing, quoting, and summarizing to formative checking systems that let students revise before final submission. At Universitas Negeri Medan, that philosophy is already institutionalized, with a dedicated Plagiarism Detection Team, tiered similarity thresholds by degree level and discipline, mandatory originality statements, and library-run programs such as Kelas Literasi, a class devoted to avoiding plagiarism through better citation and writing practice. Detection software, the study suggests, raises awareness and saves instructors time, but lasting change will come from teaching students how to write with sources, not merely how to avoid being caught.

Subject of Research: University student plagiarism behavior and the use of plagiarism detection tools in academic writing

Article Title: University student plagiarism behavior and the role of plagiarism detection tools

Article References: Machmud, M. T., Manjani, N., & Silalahi, N. (2026). University student plagiarism behavior and the role of plagiarism detection tools. Discover Education, 5(1), Article 1004. https://doi.org/10.1007/s44217-026-02180-8

Image Credits: AI Generated

DOI: 10.1007/s44217-026-02180-8

Keywords: plagiarism, academic integrity, university students, plagiarism detection software, Turnitin, similarity index, paraphrasing, citation practices, higher education, academic writing, Indonesia, educational research