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Here's a familiar scenario.It's the day before a big calculus exam, and you haven't studied for whatever reason.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 by 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.

Spaced-out Learning

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.

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.

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.

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.

And while spacing may slow the learning process because you'll be studying for more than one evening, it significantly reduces forgetting.

所以很多时候考完试就把知识还给老师了