Researchers find emotional experiences boost memory retention in new study. Photo / 123RF
Chenyang “Leo” Lin was on a trip to New Hampshire in the United States two years ago when he stopped to watch a group of squirrels darting through the trees.
That “playful moment” stuck with him. By the end of that day, he realised he could recall that moment “in vivid detail” – and also the farm animals he and his colleagues had passed earlier, on their way to their destination.
These were scenes that Lin, a doctoral student in the Reinhart Neuroscience Lab at Boston University, believes he wouldn’t normally have remembered.
He said the experience made him wonder: why does the human brain hold on to some seemingly ordinary moments while letting others slip away?
That question is at the heart of a study published in Science Advances that researchers hope will have broad practical implications – for example, in the way teachers seek to maximise information retention in their students, or how caregivers interact with people with dementia.
Written by Lin and other researchers at Boston University, the study finds that our brains selectively strengthen certain memories when they are associated with important experiences, in a mechanism known as memory enhancement.
As part of that process, the brain uses a sliding scale to decide which memories to preserve, according to the study, which relies on the findings of 10 individual studies involving close to 650 participants.
The study, which has been peer-reviewed, suggests that tying “fragile” memories – of typically routine events – to memorable or rewarding moments could prevent them from slipping away, and that doing this in a systematic way could help strengthen useful memories or weaken irrelevant ones.
“Memory isn’t just a passive recording device: Our brains decide what matters, and emotional events can reach back in time to stabilise fragile memories,” Robert M.G. Reinhart, a professor of psychological and brain sciences at Boston University and co-author of the study, said in a statement.
“Our study suggests that emotional salience could be harnessed in precise ways.”
For their study, the researchers conducted three experiments of their own and analysed data from seven independent experiments.
The team’s experiments involved showing different images to participants, with some images remaining “neutral” and others connected to cash bonuses, or “rewards” – and then giving them a surprise memory test the next day.
Other experiments involving the use of images associated with mild electric shocks were also analysed as part of the dataset.
Researchers found people were more likely to remember “fragile” events that happened just before an emotional event – in this case, the rewards or shocks – particularly when those memories had similarities to the event, such as a matching colour or visual cue.
They also showed that people were more likely to remember neutral memories that came after a major event if that event was important or meaningful.
The findings show that “emotional events don’t strengthen all nearby memories equally – the brain uses different rules depending on timing”, Lin, the lead author on the study, wrote in an email.
The memory enhancement effect of a strong experience or event mostly applied to “fragile memories that would otherwise slip away”, according to Reinhart.
If the non-core memories also carried emotional weight themselves, that effect was diminished.
Memory is an important indicator of cognitive health but experts agree that no matter your age, it is fallible and malleable.
Over our lifetimes, our brains process an incalculable amount of information and decide what to remember and what to forget, typically prioritising information that is distinctive and emotionally loaded.
Even then, our memories are subject to change.
As neuroscientists have grown their understanding of the human brain, they have also understood that there are ways to take care of it and reduce the risk of memory loss, including by exercising regularly, getting enough sleep, limiting alcohol and stress, and cultivating social ties.
Now, this study could add a new dimension to those efforts, by showing how targeted strategies can help people at all stages of life better retain their memories, researchers believe.
Maria Wimber, a cognitive neuroscientist at the University of Glasgow in Scotland, who was not involved with the study, said its findings were “intriguing”.
“To me, one big takeaway is this: our memories are not fixed snapshots. They’re dynamic, and their fate can change depending on what happens next,” she wrote in an email.
Lin hopes the study’s findings will have implications “from classrooms to clinics”.
It could change how teachers approach their lessons, he said, because it suggests that a student might have a better chance of retaining a history lesson if it is tied to a rewarding experience, “such as solving a puzzle that earns points or weaving it into a story that sparks curiosity”.
And in someone with dementia, a fragile memory of leaving one’s glasses on the table “might be anchored more firmly if paired with something relevant and meaningful”, such as a “favourite song, a family photo, or even a small gift”, Lin said.
One limitation of the study is that it doesn’t measure the underlying brain mechanisms that cause memory enhancement.
Lin said a known theory among neuroscientists who study animals is that “weak memories can be “tagged” and later stabilised if they are followed by a salient event in what’s known as “behavioural tagging”. While he said his findings align with that theory, he hopes to use brain imaging and other tools in the future to “watch the brain mechanisms unfold in real time”.
Wimber, who conducts behavioural studies inspired by animals, said the study is “important” because evidence of the behaviour tagging theory in humans has been “mixed”.
“That’s why this new work is so important,” she said.
The study is also limited by the nature of its experiments, which relied on relatively simple stimuli – like pictures of animals and tools – rather than the complex scenarios and interactions people typically encounter – and remember, or struggle to remember – in real life.
The next step, said Lin, is to test whether the brain and memory bank react in the same way in everyday situations.
Sign up to Herald Premium Editor’s Picks, delivered straight to your inbox every Friday. Editor-in-Chief Murray Kirkness picks the week’s best features, interviews and investigations. Sign up for Herald Premium here.