Exams are nerve-racking, especially for those already of an anxious disposition. The silence of the hall; the ticking of the clock; the beady eye of the invigilator; the smug expression of the person sitting at the neighbouring desk who has finished 15 minutes early. It therefore seems hardly surprising that those who worry about taking tests do systematically worse than those who do not. What is, perhaps, surprising, according to research published recently in Psychological Science by Maria Theobald at the Leibniz Institute for Research and Information in Education and her colleagues, is that it is not the pressure of the exam hall which causes the problem. It is the pressure of revision.