Scientists Figured Out Why Some Random Moments Stick With You Forever

Boston University researchers have found that emotional events can strengthen memories of ordinary moments, giving them lasting power.

The brain seems to “rescue” weak memories when they are tied to a significant or surprising experience. This new understanding of how emotion shapes recall could lead to better memory treatments and smarter learning strategies.

Why Some Memories Stick While Others Fade

Some memories come rushing back with vivid clarity, as if they happened only moments ago. Others feel distant and incomplete, like faint outlines on a page, while some remain completely inaccessible, no matter how hard we try to remember. Why does the brain preserve certain experiences so firmly while allowing others to fade away?

Researchers at Boston University may have uncovered an explanation. Their new study suggests that ordinary memories become more durable when they are linked to a meaningful or emotionally charged event—something unexpected, rewarding, or intense. For instance, if you suddenly realize your Powerball numbers have won, you are likely to recall the mundane details of what you were doing just before that moment. The findings, published in Science Advances, could pave the way for new methods to help people with memory impairments and even improve how students retain challenging information.

Stabilizing Fragile Memories Through Emotion

“Memory isn’t just a passive recording device: Our brains decide what matters, and emotional events can reach back in time to stabilize fragile memories,” says Robert M.G. Reinhart, a BU College of Arts & Sciences associate professor of psychological and brain sciences. “Developing strategies to strengthen useful memories, or weaken harmful ones, is a longstanding goal in cognitive neuroscience. Our study suggests that emotional salience could be harnessed in precise ways to achieve those goals.”

In their paper, Reinhart and his team illustrate this idea with a scene from Yellowstone National Park: a hiker unexpectedly encountering a herd of bison. According to the researchers, the awe of that experience can help preserve not just the extraordinary sight itself but also the smaller, seemingly insignificant details surrounding it—like noticing a rock on the trail or catching a glimpse of an animal in the brush.

“The question is, What are the mechanisms for that?” says Reinhart, who’s also a College of Engineering associate professor of biomedical engineering and a faculty member at the BU Center for Systems Neuroscience. “That’s what we tried to uncover, how the brain selectively strengthens those fragile memories.”

How the Brain Selects Which Memories to Preserve

While most of us know that special moments get a revered spot in our memory banks, researchers have been divided on concepts known as retroactive and proactive memory enhancement—the prioritization of memories immediately before or after a big, or salient, event. Previous studies have disagreed on whether or not weaker memories are stabilized, or made easier to recall, by attachment to a more prominent one.

Reinhart says the latest project, which included close to 650 participants, ten individual studies, and the use of artificial intelligence to analyze a broader set of data, is the first to definitively show that memory enhancement does happen. One major difference with past studies: they found the brain uses a sliding scale to decide which memories to preserve. Many of the team’s experiments involved showing participants dozens of images—connected to different levels of rewards—then giving them a surprise memory test the next day.

Proactive vs. Retroactive Memory Enhancement

With things that occurred after an event, proactive memories, the strength of recall seemed to depend on the emotional impact of the big moment itself—the more enduring the salient event, the more likely everything after it was to be remembered. That didn’t apply when reaching back to the things that happened in the runup, the retroactive memories. They were more likely to be cemented if they had similarities—perhaps a visual cue, like a matching color—that connected them to the pivotal event. According to Reinhart, it’s the first validation in humans of “graded prioritization, a new principle of how the brain consolidates everyday experiences.”

“For the first time, we show clear evidence that the brain rescues weak memories in a graded fashion, guided by their high-level similarity to emotional events,” says Chenyang (Leo) Lin (GRS’30), the paper’s first author and a doctoral student in the Reinhart Lab. “It’s not just timing that matters, but also conceptual overlap.”

The researchers also found that if any secondary memories carried emotional weight themselves, the memory enhancement effect was diminished. “The brain seems to prioritize fragile memories that would otherwise slip away,” says Reinhart, who has published a series of highly cited papers on how memory functions. Much of his research has also included brain stimulation—using noninvasive techniques to improve working and long-term memory in older adults or to curb obsessive-compulsive behavior.

Rescuing Memories; Improving Test Scores

Although the latest study was focused on uncovering a basic mechanism guiding how memories are encoded, Reinhart says the work could lay the foundation for future clinical and other real-world studies and interventions.

“The discovery has broad implications for both theory and practice,” says Reinhart. “In education, pairing emotionally engaging material with fragile concepts could improve retention. In a clinical setting, we could potentially rescue memories that are weak, way back in the recesses of our mind, because of normal aging, for example. You can flip it, too, for people with trauma-related disorders—maybe you don’t want to rescue a distressing memory.”

Reference: “Salient experiences enhance mundane memories through graded prioritization” by Chenyang (Leo) Lin, Wen Wen, Phillip (Xin) Cheng, Seth Schallies, Shrey Grover and Robert M. G. Reinhart, 24 September 2025, Science Advances.
DOI: 10.1126/sciadv.ady1704

Reinhart’s research is funded by the National Institutes of Health, the International Obsessive-Compulsive Disorder Foundation, the AE Research Foundation, and philanthropy.

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