Memories will fade as you age, until only the basic gist remains

BIRMINGHAM, United Kingdom — Although some people say they can still remember things that happened decades ago with perfect clarity, a new study finds that’s not how the brain typically works. Researchers in the United Kingdom have discovered new insight into how people bring back old memories. Their findings reveal, as more time passes, only the most meaningful elements of those experiences stick in our minds.

Researchers at the Universities of Glasgow and Birmingham say it’s natural for a person’s memories to become less vibrant over time. At a certain point, only the main gist of a past event eventually remains. If fact, frequently thinking about recent experiences actually boosts what the scientists call the “gistification” of our memories.

What do people actually hold on to in their memory?

Researchers explain that memories are not carbon copies of a person’s past experiences. Instead, experts believe the task of remembering something is a very reconstructive process and the details could even change slightly every time that person brings it back to mind.

“Many memory theories assume that over time, and as people re-tell their stories, they tend to forget the surface details but retain the meaningful, semantic content of an event,” says Birmingham’s Julia Lifanov, lead author of the study, in a university release.

“Imagine reminiscing about a pre-COVID dinner with a friend – you realize that you cannot recall the table décor but know exactly what you ordered; or you remember the conversation with the bartender, but not the color of his shirt. Memory experts call this phenomenon ‘semanticization’.”

In the new study, researchers created a computerized task which measured how fast people can recall specific characteristics of a visual memory. The team asked participants to determine as fast as possible whether an image was in color or greyscale, a perceptual detail. They also had to determine if the images contained animate or inanimate objects, a semantic characteristic.

The group then learned word-image pairs connecting to these different images which scientists would say to cue the memory of each picture. Study authors conducted the tests immediately after participants learned the matching words and again two days later. The results reveal a person’s reaction time was much faster when recalling meaningful, semantic details of a memory.

Certain details fade away fast

Study authors add that the findings show human memory is biased towards retaining meaningful content above all else. Previous studies have discovered that brain signals also show this pattern.

“Our memories change with time and use and that is a good and adaptive thing. We want our memories to retain the information that is most likely to be useful in the future, when we encounter similar situations,” explains Professor Maria Wimber from the University of Glasgow.

When the participants returned after a two-day rest, their memories showed even more bias towards semantic details. The study finds people were also much slower at answering questions involving perceptual details, like the color of someone’s shirt.

Researchers note that the differences were less apparent among people who repeatedly viewed the images before taking the tests. The team believes this may be an important factor when studying the impact of health and disease on human memory. In the case of patients suffering from PTSD, they tend to over-generalize their traumatic experiences to novel situations. For eyewitnesses to events like crime, memories can become biased as the person gives frequent interviews and is forced to recall the event several times.

On a positive note, researchers find testing oneself before an exam (with flashcards for example) can make an image stick longer in the mind. Rest and sleep can boost this effect even more.

The study appears in the journal Nature Communications.