Many of us remember brewing cups of coffee to help us stay awake during the occasional all-nighter to pass a test or finish a presentation. We've also used word repetition, created index cards, and even played a recording of lectures as we slept. Now, researchers at Baylor University have found a better memory hack to recall information: tell a friend what you've learned.

“This has to be actively replaying or re-generating the information — for example, by telling someone the particulars, as opposed to just simply re-reading the textbook or class notes and studying it again later,” said Melanie Sekeres, lead author of the study, and Baylor psychologist, in a statement.

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The brain prioritizes "rewarding" memories over others that don't seem to benefit us, and reinforces these rewarding memories by replaying when we are at rest. For example, our brain will more likely remember social activity because it's seen as a "high reward" in our mind. When we interact with another person, our brain is more engaged, and those memories will be categorized with the importance of the interaction. So if we try to explain a test concept to our friend, we’ll be more likely to retain the information, which leads to better long-term memory.

In the study, published in the journal Learning and Memory, Sekeres and her colleagues put this theory to the test by recruiting 60 participants with an average age of 21 and dividing them into three groups to watch an obscure foreign film. The 24-second clips from 40 films contained brief scenes of normal, everyday events, such as a family having dinner, or kids at a park. The students were then asked what they remembered about the films after delays, which ranged from several minutes after the showings to seven days later.

Not surprisingly, all participants recalled less about the details and the concept of the films after a longer delay. They forgot the perceptual or “peripheral” details from the films more quickly compared to the films' central themes. Meanwhile, the second group of students, who were given cues before being asked to recall the films, did better at retrieving faded memory of the peripheral details. However, their retention of central information was not much different from the first group, who did not have such cues.

Lastly, the third group, who reinforced the memory of the films by telling someone about them soon after watching, remembered both central and peripheral information better over time. This is known as the “replaying” method — telling someone what we’ve learned is an effective way to study, rather than just re-reading the textbook or class notes.

“We tell students to test yourself, force yourself to tell someone about the lecture. Even by writing out some questions for yourself about the information, then later answering them yourself, you are more likely to remember the information," said Sekeres.

It's important to note forgetting some details is normal, and it's also normal to become somewhat more forgetful as we age. The brain is adaptive; we recall important things, and tend to forget the unimportant details. Sekeres suggests this is because we don’t want our brain to search through tons of useless information.

Read More:Why The Brain Remembers And Forgets, Plus 3 Ways To Improve Memory

We don’t permanently forget what we’ve learned, we just don’t have immediate access to some memories. Next, Sekeres and her research team are looking at functional magnetic resonance imaging (fMRI) to see how brain activity changes over time as memories age, and lose peripheral details.

"Identifying changes in patterns of brain activity that accompany normal forgetting in the healthy brain will help us to understand differences between normal and abnormal memory processing,” she said.

One thing we do know: our memories do change over time, for better or for worse.

Source: Sekeres M et al. Want to Ace an Exam? Tell a Friend What You Learned. Learning and Memory. 2017.

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