Some students believe that they can "beat" Turnitin by employing various tactics. Instructors should rest assured that these tactics do not work as our algorithms take such "tricks" into account. In addition, the best practice for ensuring that students are not able to "beat the system" is to review all Originality Reports - regardless of the percentage shown as the Similarity Index. Instructors who look at the Originality Reports will be able to tell if something untoward has occurred.
What tricks do students try?One trick is to replace a common character like "e" throughout the text of their paper with a foreign language character that looks like an "e" but is actually different (for example, a Cyrillic "e"). This method does not work because our algorithms replace such characters with the corresponding standard English character. The special character will still appear in the Originality Report; however, the word it is in will have been matched against words containing every character that looks like that character. This allows us to show you matches to words with both the special character and the standard character.
Another trick (touted by a video on the web) is to use Word Macros to disguise copied text. This method also does not work since Turnitin's algorithms strip macros from Microsoft Word Documents for Word 2003 and below. When we strip a macro from a Word file, whatever character the student originally had in the file will appear. For instance, one of the videos recommends starting with a "~e" and replacing it with a standard "e" using macros. When we strip the macros the "~e" will appear in the paper. This means the "~e" will appear in the Originality Report, GradeMark, and the file available for you to download from the service. For Microsoft Word 2007, we don't accept macros-enabled (.docm) files (we do accept the standard .docx files).Another method consists of replacing all the spaces in a paper with invisible (white) text. This also does not work since Turnitin will not accept papers that appear to have this condition based on abnormal word lengths. In addition, the text-only Originality Report displays all text regardless of the color used by the student.
A fourth possible trick is to put quotation marks around the entire document. This does not work because Turnitin does not automatically exclude quoted material. Only the instructor can change the default setting to exclude quoted material from Originality Reports. The Originality Report would also show the quotation marks at the beginning and end of a paper in the same size text as the rest of the paper. If the instructor chooses to exclude quoted material, Turnitin displays a warning when a large percentage of a paper appears within quotation marks.
The Turnitin algorithms are updated on an on-going basis to make the Originality Reports more accurate and informative. As an instructor, your best defense is to ALWAYS review your students' Originality Reports - even for Similarity Indexes shown as zero. All of the "tricks" discussed here rely heavily on the idea that the instructor will not look at the Originality Report. All attempts to game the system become pretty obvious when the instructor examines the Originality Report. So make a quick scan of each Originality Report part of your standard practice when evaluating papers.
UPDATE: This blog post was featured in the New York Times article, "To Stop Cheats, Colleges Learn Their Trickery" by Trip Gabriel.