The paper is turned over and none of the questions make sense. Or the exam hall cannot be found, or the subject is one you never studied. Exam dreams are so common that many people still have them decades after their last test. In a 2003 survey of 1,181 Canadian university students, 45% had dreamed of failing an examination; it was more common among women and among younger students.

The folk reading. Older dream books were encouraging. Felix Fontaine's Golden Wheel Dream-book (1862) says that attending school in a dream is "a sign of advancement and good fortune", and that if you find it hard to learn, you will have trouble getting along but "will rise at last". Sigmund Freud, in The Interpretation of Dreams, passed on an observation by a colleague, Dr Stekel of Vienna: exam dreams come only to people who passed the exam, never to those who failed it. Freud's reading was that the dream reassures. When we face some new test of responsibility, it reminds us of an old fear that turned out to be groundless. He added that his own exam dreams were about subjects he had passed.

What research says. In 2014, a team led by the sleep researcher Isabelle Arnulf surveyed medical students in Paris about the night before their entrance exam. Of 719 who answered, 60.4% had dreamed about the exam, mostly about things going wrong: being late, forgetting answers. Those who had such a dream did slightly better in the real exam, and students who dreamed about the exam more often during the term also scored higher. The researchers suggested that rehearsing a stressful event in a dream may give a small cognitive benefit. It is one study, and an association rather than proof, but it is the opposite of the idea that a failed exam in a dream is a bad sign.

If dreams like these are frequent, distressing or stopping you sleeping, talk to a doctor or a mental-health professional. This page is educational and is not a diagnosis.