We’ve all heard it said that learning medicine is like drinking from a firehose. Yet many students and schools don’t use one of the most effective study techniques available to them. Spaced repetition is a powerful, evidence-based study technique that can enhance learning and long-term retention of medical knowledge. Medical students and schools could both benefit from understanding and using spaced repetition to produce more knowledgeable and better-informed doctors.

Over a hundred years ago, a German psychologist, Hermann Ebbinghaus, used careful experiments to determine how learning and forgetting works. From these experiments, he described a “forgetting curve” in which “large amounts of forgetting occur quickly, followed by a more slow and steady decline in retention.” Forgetting happens almost immediately after a student learns something. Within 20 minutes of learning some new information, students can only recall about 60 percent of the information they just learned. By 9 hours, retention is less than 40 percent, and 20 percent by 10 days.

These results led to another key observation: The temporal relationship of studying matters. “Learning events that are repeated over time result in more efficient learning and greater retention compared to exposure to a single bolus of material,” a psychological finding termed the “spacing effect.” A recent article remarked that, “The spacing effect is arguably the most replicable and robust finding from experimental psychology. Hundreds of articles, including a number of reviews and meta-analyses have found a spacing effect in a wide variety of memory tasks.” Spaced repetition, a technique in which students review material according to a schedule determined by the spacing effect, has been found to be effective in numerous educational contexts.

It shouldn’t be surprising, then, that some researchers have investigated the spacing effect in medical education. In one randomized controlled trial of the spacing effect, Kerfoot et al. found that spaced learning improved the retention of clinical knowledge by medical students at Harvard. After a one-week urology rotation, the students were split into two groups. Each received a series of spaced review emails, with one group getting questions on one-half of the topics in urology and the other group getting questions on the other. At the end of the year, each student group did significantly better on the topics that they received questions about. This study did not attempt to compare spaced repetition with more typical study techniques, but did show that a relatively small time investment into spaced studying could lead to significantly improved retention. At the resident level, where retention of knowledge is arguably even more important, the spacing effect has been shown to work as well.

And spaced repetition doesn’t require the instructor-driven methods used in these studies. Many med students, on their own initiative, now use free, open-source flashcard apps, such as Anki and Mnemnosyne in their studies. These programs that use an algorithm to exploit the spacing effect and optimally schedule their reviews of class material; ideally, the program would prompt students to review a fact as soon as they were in immediate danger of forgetting it. Students have been able to use these tools for all aspects of medical learning, from biochemistry to clinical guidelines. These platforms are also fertile ground for student collaboration to create shared resources (such as standard flashcard “decks”) to pool their learning efforts.

The catch, however, is that the spacing effect requires patience and diligence. And many students have gotten quite far in our academic careers by doing the exactly the opposite, through cramming and “hit and run” studying. Why is that? Well, the simple truth is that massed learning, more commonly known as cramming, does work in the short term. You can load up your memory with information, and some of it will stay there for a time. But as anyone who has ever crammed for a test can confirm, the gains are merely temporary. This is good enough to pass weekly quizzes and perform well on tests without strong cumulative elements — and since many classes are set up that way, including in med school, cramming is often one way to get a good grade.

But all those efforts yield little long-term knowledge. By the time they arrive in medical school, most students have forgotten the majority of what they learned in college courses. Students routinely need to re-learn massive amounts of forgotten information before taking their board exams, and residents eventually forget much of what they learned in medical school outside their specialty. All this translates into vast amounts of time wasted.

Fortunately, spaced repetition is low-hanging fruit that both individual students and institutions can employ to enhance medical education. Students are already investing time in electronic flashcard programs to enhance their retention for board exams and beyond. As more students understand the tradeoffs between spaced studying and cramming, they can make more informed decisions about how they want to navigate learning in medical school.

Schools, for their part, have opportunities to facilitate the use of spaced repetition. We certainly can’t expect busy medical schools to dedicate time to teach about the psychology of learning and spaced repetition. But there are ways for schools to lower the barrier for students adopting this methodology for themselves. One way is to use cumulative exams rather than weekly quizzes, so that they at least do not penalize students who choose to focus on long-term retention instead of cramming. Another is to increase flexibility in their preclinical courses. Pass-fail grading, now widely adopted in preclinical courses, gives students the freedom to focus on their long-term learning rather than inefficiently studying towards short-term exams. Increased scheduling flexibility, with streamed classes and fewer mandatory lectures, can also give students the time they need to study for the long-term.

The power of modern medicine is in large part the result of an explosion of our understanding of the human body. As a result, medical education will have to continue to grapple with how to teach students and residents ever-increasing amounts of information to train them as clinicians. By harnessing the power of spaced repetition, students and medical schools alike can work to learn more effectively and create better-informed doctors.

Peter Wei is a radiology resident. Alex Chamessian is a medical student. They are authors of Learning Medicine: An Evidence-Based Guide.