Tension is rising in the Harford household as exams approach and we try to persuade Miss Harford Sr to relax, and Miss Harford Jr to be slightly less relaxed. I'm sure many readers have vivid memories of the exam room, recent or otherwise.
But here's a question about exam technique that suggests a much wider lesson. In a multiple-choice test, you sometimes write down an answer and then have second thoughts. Is it wise to stay with your first instincts, or better to switch?
Most people would advise that the initial answer is usually better than the doubt-plagued second guess. Three-quarters of students think so, according to various surveys over the years. College instructors think so too, by a majority of 55 to 16 per cent. The 2000 edition of Barron's How to Prepare for the GRE Test is very clear that students should be wary of switching. "Experience indicates that many students who change answers change to the wrong answer."
This confidence would be reassuring, were it not utterly erroneous. Researchers have been studying this question since the 1920s. They have overwhelmingly concluded both that individual answer changes are more likely to be from wrong to right, and that students who change their answers tend to improve their scores.
This gap between perception and reality is stark enough to have earned a name: the "first-instinct fallacy". No doubt our first instincts are often right, but when we start to have second thoughts, the second thoughts are usually occurring for a reason. It is better to switch. So why don't we?
Justin Kruger, a psychologist at New York University, has been studying this question. (Prof Kruger is more famous as co-discoverer of the Dunning-Kruger effect: people who are incompetent are too incompetent to realise how incompetent they are.) With his colleagues Derrick Wirtz and Dale Miller he replicated the longstanding findings that college students believe you should trust your first answer in a multiple choice question, and yet that switching to a second answer tends to improve your grades.