Here's a familiar scenario. It's the day before a big calculus exam, and you haven't studied for whatever reason (short on time, too many other exams packed into the same day, etc.). Around 10 p.m., you finally sit down to review the calculus materials. Six hours later, you catch a short "nap" before rushing to school. You take the exam, and it seems to go fine. Although it wasn't your best effort, you pass and promise not to repeat the cycle when it's time for your next one.
This is what's known as cramming. And while students, parents and educators have long known it's not ideal, in desperate circumstances, it works to some degree. And by some degree, we mean it might save your GPA. But cramming doesn't provide long-term learning, according to Dr. Robert A. Bjork, distinguished research professor in the department of psychology at UCLA where he focuses on how we learn versus how we think we learn. (Spoiler: We are usually wrong.)
"[Cramming] can have pretty dramatic effects on the exam," Bjork says. "It will work in the sense of performance on an exam administered right at the end of cramming. [Students] get an impression that it really works, but it just works on the short term. It's accompanied with a dramatic forgetting rate after that." This is especially problematic when one lesson provides foundational information for the next, like in a math or language class.
Forgetting most of what you learned is not the only downside to cramming. Researchers have found that losing sleep while pulling an all-nighter also leads to residual academic problems for days after the cramming session. You can imagine the negative effects of an ongoing cycle of procrastination and cramming.
More than a century of research shows that if you study something twice, retention goes up, Bjork explains. Studying and then waiting before you study more produces even better long-term memory. This is called the spacing effect.
"It's often something students don't understand," Bjork says. Rather than reviewing material right away, students benefit from spacing out their study sessions. There are many arguments about why spacing works better for long-term retention. One relates to encoding.
When a student studies something from a book and reviews it immediately, the student will encode the information in the same way, Bjork explains. However, the more ways students can encode information, the better they will understand it and the longer they will know it. This means that even studying the same material in two locations can help them encode it in different ways; therefore they learn it more successfully.
Another idea is that the harder it is for our brain to recall something, the more powerful the effects of that recall will be for long-term learning. For example, if you are at a meeting and encounter someone new, you might recall their name immediately, which probably won't help you remember it the next day. However, if you need to recall the person's name an hour into the meeting and do so, you'll have a better chance of remembering it a day or a week later because you had to put in effort to recall it.
A third reason why spacing works is that people pay less attention to the second presentation of material they have just seen because the information is already familiar. When the material is spaced out, it's no longer as familiar, so people pay more attention.
Dr. Will Thalheimer, founder of Work-Learning Research, which focuses on research-based innovations in learning evaluations, explains that when it comes to learning, presenting material more than once is beneficial, but doing it over time is even better and "facilitates long-term remembering." And while spacing may slow the learning process because you'll be studying for more than one evening, it significantly reduces forgetting.
However, many students continue to opt for cramming and believe in its efficacy.
A 2009 study by UCLA's Dr. Nate Kornell found that spacing was more effective than cramming for 90 percent of the participants; just 6 percent of those who crammed learned more than those who studied using the spacing effect. In three experiments, researchers tested spacing against cramming, yet despite the findings in favor of spacing, participants believed that the cramming style was more effective.
Mixing It Up
If the spacing effect sounds like a lot of waiting around to review material, recent studies have shown the positive effects of mixing up different material while studying. This concept, called interleaving, consists of working on or studying one skill for a short period of time, then switching to another one, then maybe a third, then back to the first.
A 2015 study tested interleaving in nine middle school classrooms teaching algebra and geometry. A day after the lesson for the unit was complete, the students trained with interleaving scored 25 percent better than students who received standard instruction. A month later, the interleaving group was up 76 percent.
This is great news. Studying for an exam or completing a big project doesn't need to feel so daunting, and interleaving has benefits for writing, too. Rather than trying to block out two hours to study for a math test, study math for 30 minutes before you move to French and then work on an essay. Go back to math later.
"That produces substantially longer and better retention," Bjork says. "It has a lot of implications that we are exploring."
There is a message here for teachers as well as students. Instead of teaching a topic in a block and going to the next topic, teachers can spend a short time on a topic, go on to others then return to the earlier topics.
"There is a lot to learn about how to learn," says Bjork. "People's intuitions are not the best guide."