Professor Shahriyārī had related to us that when he was in the first or second grade, he became aware that one of his classmates was cheating during a spelling test by looking over his shoulder onto his work. He said that he was not comfortable knowing that the grade of someone who has not studied the lesson would be as good as his grade. And so he made some mistakes on purpose so that the cheat would also make those mistakes, but then quickly corrected the errors on his sheet before handing it in to the teacher.