Turnitin software, which is used by thousands of universities worldwide, extracts text from submitted essays and checks it against other sources, such as online documents.

However, the study conducted by a researcher at California State University suggests that such measures should not be regarded as a "silver bullet" in the battle against "deviant" academic practices.

Robert J. Youmans, a cognitive psychologist, says in the paper published in the journal Studies in Higher Education that he expected to find that fewer students would cheat if they were warned that their work would be scanned.

This proved not to be the case.

"One explanation is that students who plagiarized did not have high confidence that the system would detect the plagiarism in their writing," he says. "A second explanation is that the students who plagiarized were, for lack of a better word, desperate."

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Dr Youmans carried out two tests involving final-year psychology students at California State University, Northridge. For the first, he divided the 90 participants into two groups, telling one half that their work would be scanned using Turnitin and the other that it would be checked by their tutor.

For the second study, he warned all 37 participants that their work would be scanned.

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Prior to both studies the students were given information about how Turnitin worked and signed "honour contracts" promising not to cheat. Yet despite this, Dr Youmans reports, the percentage of papers that contained at least 10 per cent unoriginal writing was 31 per cent and 46 per cent respectively.

Four students turned in papers that "clearly violated plagiarism rules": all were among the groups warned that Turnitin would be used.

When challenged, one said he had deliberately plagiarised because he ran out of time, while the others said they did not know how to use other people's work fairly.

Dr Youmans writes: "Even when combined with aggressive teaching methods, the Turnitin detection system failed to provide a sufficient deterrent."

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He adds: "It is important that [scholars] realize that they are unlikely to find a so-called 'silver bullet' in the form of a system that, once adopted, will eliminate plagiarism."

Jonathan Bailey, founding editor of the Plagiarism Today website, said that plagiarism-detection tools work best ¡°when they aren't used as a mysterious plagiarism cop designed to play 'Gotcha' with plagiarists¡±.

¡°Instead, they need to be incorporated into plagiarism education and used as a tool to teach what plagiarism is, how to cite sources, when to cite and so on,¡± he said.

¡°This is why many schools are actually incorporating plagiarism detection into the writing process, having students submit their work to the system so they can get results before grading.¡±

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He added that software such as Turnitin would continue to have some role in enforcement, but that it provided much better value for money when it was used as a teaching aid.

¡°Incorporated into a much larger process for teaching and dealing with plagiarism, these systems can be worth their weight in gold. It is just a matter of how they are used,¡± he said.

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