How your memory works, and how it changes as you age

Memory lapses happen at every age, but recent missteps by Biden and Trump have sparked questions about memory and aging

By Caitlin Gilbert, Gretchen Reynolds, Richard Sima, and Teddy Amenabar

Have you ever mixed up the names of your children? Are you struggling to remember key dates or the year a loved one died? Recent news of mental lapses by President Biden and Donald Trump have sparked a national conversation and social media posts about what memory mistakes really mean about aging and brain health.

Matt Griffin, 54, who works in communications for a school district in Vancouver, Wash., said he thinks about his father, Grady Griffin, every day, and he remembers what he was doing the night his father died. But he can’t remember the exact date of his death from terminal brain and lung cancer. (He looked it up, and it was 19 years ago this month.) “I don’t think it’s reasonable to expect everybody to recall everything,” he said. “The thing I know that is ever present is my dad is gone, and I miss him.”

Experts agree. Memory, no matter what your age, is fallible and malleable. Our brain processes incalculable amounts of information at a given time, and there’s simply not room for all of it to be stored. And surprisingly, the act of forgetting is an important aspect of memory.

Mental acuity has been a flash point affecting both presidential candidates, but it has taken on new urgency following a special counsel report into Biden’s handling of classified documents. The report noted that Biden, 81, had trouble recalling the years he served as vice president and didn’t remember the exact date his son Beau had died, among other issues. Trump, 77, has struggled with his memory lapses, most recently confusing former U.N. ambassador Nikki Haley, his last-remaining rival for the Republican presidential nomination, with former House Speaker Nancy Pelosi (D-Calif.).

The Washington Post interviewed several memory experts. They noted that the cognitive abilities of Biden and Trump can’t be evaluated based on anecdotal memory lapses. Formal evaluations are needed to truly assess someone’s brain health. But they noted that memory lapses at any age are surprisingly normal and, for most people, aren’t a signal of mental decline.

“Most of us have memory slips all the time,” said Earl K. Miller, professor of neuroscience at the Massachusetts Institute of Technology. “We can’t remember where we put our car keys. We can’t remember dates or names. But we don’t notice the mistakes when we’re young. It’s when people get older that mistakes in memory seem to have more significance. Memory lapse really is normal at every stage of life.”

How our memories work

Our brain can process and hold vast amounts of information, but it has limits. Facts, dates, and events can be stored and recalled for days and weeks — or even across a lifetime. As new memories are created, the brain must prioritize important memories, making it more difficult to recall less important details or events.

When we encounter new information, our brains encode it with changes in neurons in the hippocampus, an important memory center, as well as other areas. These groups of cells work together to hold onto the specific information of a memory, creating a memory trace, known as an engram.

Much of this information is forgotten unless it is stored during memory consolidation, which often happens during sleep, making the memories more stable and long-term. These neurons become active when the event happens and, “when you recall the memory, they’re active again,” said Sheena Josselyn, a senior scientist at the Hospital for Sick Children in Toronto who studies memory.

Unlike a computer, our memories are not fixed and permanent. Each time we access and reconsolidate a memory, it is subject to change. Sometimes, when we have conversations about memory or see news footage related to it, the mind can recombine these experiences and wrongly store them as memories.

That’s why the stories we tell about our real memories may shift and change over time, and misremembering is common. Mitt Romney once shared a memory about a jubilee in Detroit that took place before he was born. Hillary Clinton once spoke of being under sniper fire in Bosnia, only to later admit that she had her facts wrong.

“Memory is never perfect even when it seems perfect,” said Miller. “We remember what we want to remember. That’s true for everyone at every stage of life. If we remembered everything, it would be too much for our brains. Our brains would be completely overwhelmed. We always have selective memory.”

Why forgetting is necessary

What we remember tends to be distinctive, emotionally loaded, and deemed worthy of reflecting upon in our heads after the event happened. Our memories are centered on our life stories and what has affected us the most. As a consequence, more insignificant details are often cast off.

Our imperfect recollections are the price we pay for a memory system that is adapted to the things we want to remember in our everyday lives.

“We don’t want a memory system that’s going to encode every single trivial detail of our experience and retain that over time,” said Daniel Schacter, a psychology professor at Harvard University and author of “The Seven Sins of Memory,” which covers the common ways our memories are forgotten or distorted.

“The possible consequences of retaining every detail of every experience might be a very cluttered mind and an inability to sort through relevant and irrelevant experiences,” Schacter said. “So the fact that we don’t encode and retain typically every detail of every experience leaves us prone to forgetting, but on balance is probably a good thing because we end up, by and large, remembering the most important things.”

According to Josselyn, forgetting allows us to identify important knowledge from our experiences as we age.

“We tend to lose the non-important things so we can extract the important principles,” Josselyn said. “Rather than remembering the time and details, we remember the concepts and the generalized principles.”

How memory changes as we age

“It’s very clear that there are a number of changes that occur with aging and cognition that are just part of getting older,” said Bradford Dickerson, a professor of neurology at Harvard Medical School, who’s studied cognitive super-agers.

Declines in the ability to think and remember among the elderly are broad and almost universal, he continued. “There’s just not much cognitively that’s better in an 80-year-old than in a 20-year-old.”

“The raw power of our memory tends to peak in our early twenties,” said Thomas Wisniewski, a professor of neurology, pathology, and psychiatry at NYU’s Langone Health. Mental acuity begins a long, slow slide from then on.

Some of this decline probably is due to structural changes that occur throughout the brain, starting by midlife, said Jason Shepherd, an associate professor of neurobiology at the University of Utah. Synapses, the connections between neurons, can weaken. Brain cells may die. Some of the brain’s tissue becomes tattered and thin.

The most obvious impacts of age involve processing speed, Dickerson said. Everything gets slower. “And that’s not just cognition. Movement slows. Sensory processing slows.”

The effects can be seen most clearly during the speech, he said, an activity that takes place at relatively high speeds and requires considerable mental juggling and swift recall. “But word retrieval becomes more difficult with age, so people stumble while talking,” he said. “It’s not that they don’t know what a word means, but retrieving it takes more time.”

Aging also “magnifies any vulnerabilities that already exist,” he said. “If someone had difficulties speaking as a young adult, for instance, then getting older is likely to worsen the problem.”

At the same time, older brains can be especially susceptible to stress, distraction, and fatigue, he said, all of which worsen memory recall.

Still, older brains can often compensate for their growing weakness, he and other researchers point out. “There’s evidence that older adults can strategically focus memory” on the most important information, Schacter said.

Older brains often become more adept than younger brains at filtering irrelevant information or at making connections between experiences, the researchers agreed, because they’ve had more of them.

“An older brain is a wiser brain. It has experience to draw on,” Miller said.

“The thing I’d most like people to understand is that, yes, there is some normal cognitive decline during aging,” Shepherd said. “But it’s not a disease state. It’s part of life.”

Wisniewski agreed. “We should not be prejudiced about age” and thinking ability, he said. “It’s true that age is the primary risk factor” for Alzheimer’s disease and other types of memory loss. “But many very elderly people remain quite sharp, mentally, and they also have a great depth of wisdom and experience.”

Why do we often forget dates and names

Some types of information are harder to hold onto. Remembering dates and names can be particularly difficult unless we make a point of rehearsing and strengthening those memories, experts say.

Memory for “when an event happened is something that for everyone, regardless of age, is one of the most vulnerable aspects of memory,” Schacter said.

Names are also harder to recall because they “have no inherent meaning — they’re kind of arbitrary,” Schacter said. (A phenomenon called the Baker-baker paradox highlights that it’s harder to remember the name Baker than if the person’s job was a baker because we have more information about the occupation than the name.)

The inability to retrieve names, even those we know well, is a common complaint of aging. Though often something people find worrisome, by itself, this is not a sign of cognitive issues, Schacter said.

On social media, some people criticized the special prosecutor for singling out Biden’s memory lapses related to the death of his son, noting that they also have forgotten the date or year a family member died. “Trauma does that,” one person wrote.

“Pretty bad for the special counsel to criticize Biden for not recalling the details of his son’s death,” Michael Lawson, 36, an architect who lives in Roanoke, wrote on Threads. “My mom died more than ten years ago, and the day of her death is very memorable but not one I actively maintain in my memory library.”

In an interview, Lawson said his mother, Susan Lawson, died at 53, three years after being diagnosed with ovarian cancer.

Lawson said he remembers his mom’s hospice room, the table where the family would gather to eat a meal or play board games, and the window that looked out to a garden.

“The visual of that room is one of those things that stands out,” Lawson said.

“The granularity of the detail isn’t something that I need to go back to,” Lawson said. “The fuzzy memories, the way I’m not totally clear on exactly what she said, here and there, is fine with me.”

The Washington Post