Study: The secret way emotions unlock hidden memories

You might forget the mundane details of your days, but they’re still hanging out in your brain—they just need a tug of emotion to come spilling out.

That’s what a team of New York University researchers found when they tested 119 people—split into groups of 30—to see how associating an experience with an emotional response would change the way people remembered experiences in their past. The study was published in the journal Nature.

The researchers first showed each group of people 60 images consisting of 30 animals and 30 tools. Then they showed the subjects another 60 images—same topics, but different animals and different tools. This time, though, people got small shock when they saw a picture that fell into one category—some were shocked by animals, others by tools. The shocks associated the images with fear, as measured by the increased sweat levels of the participants.

Later or the next day, the subjects returned for a surprise memory test. They were asked to identify the animals and tools they had seen. As expected, people remembered the animals or tools that they had received shocks for. But people also had a better memory of that category from the first set of images, when they hadn’t been shocked at all.

This is called behavioral tagging, explains co-author Joseph Dunsmoor: Many experiences we have are not significant, and there’s no reason for them to persist in our long-term memory, Dunsmoor says. But your brain can pull up that memory and strengthen it if a similar experience provokes an emotional response down the line.

This has been previously tested in rats, but not humans, Dunsmoor says. The tests on rats suggest that the emotion doesn’t have to be a negative one—their version of the emotional tag was the pleasant novelty of being allowed to run in an open field.

The finding is not a silver bullet when it comes to triggering witnesses’ recall in criminal cases though. The emotions tested here are light ones, Dunsmoor says. Serious trauma can actually have the opposite effect, of blurring memories and causing a person to forget details.

This study didn’t test how people could use this understanding to their benefit for developing better memories. But Dunsmoor does suggest that if you’re trying to remember something, attach it to a new experience, or to something emotionally meaningful and relevant to you.

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