There’s a paradox in memory science: Empirical evidence and life experience both suggest older adults have more knowledge of the world. However, in laboratory settings, they generally perform worse on memory tests than younger adults. What can explain the disparity?
The answer might be “clutter,” according to a review of memory studies published Friday in the journal Trends in Cognitive Science.
Tarek Amer is a postdoctoral fellow at Columbia and Harvard Universities and the review’s first author. While some scientists think that as adults grow older, they begin to form “impoverished memories” — memories that contain less information relative to the memories of younger people — Amer and his colleagues have a different view. Instead, “older adults might actually be forming too many associations between information,” Amer said.
Compared to young adults, healthy older adults (defined in the paper as 60 to 85 years old) process and store too much information, most likely because of greater difficulty suppressing irrelevant information, the analysis found. This difficulty is described as “reduced cognitive control” and can explain the cluttered nature of older adults’ memory representations.
“It’s not that older adults don’t have enough space to store information,” Amer said. “There’s just too much information that’s interfering with whatever they’re trying to remember.”
This explanation stems from and is supported by the team’s review of several behavioral and neuroimaging studies. Their paper “makes a compelling case that, as we get older, part of the problem is that we get less selective,” said Charan Ranganath, a professor at the University of California, Davis Center for Neuroscience. Ranganath was not part of the new paper.
It’s a phenomenon that, on some level, is experienced across ages.
“A great deal of everyday forgetting is not necessarily because we cannot form new memories, but rather, we can’t find what we want when we need it,” Ranganath said.
“Many of us have the experience of being unable to recall a person’s name or locate where we left our keys, only to have that information pop into our head later,” he added.
This happens because people form many similar memories, such as all the people they have recently met or all the places they could have put their keys. That makes it challenging to select the correct information, Ranganath explains.
Amer and colleagues argue this happens more frequently as people get older, not because they are losing brain plasticity or progressing toward amnesia, but because of these “cluttered memoryscapes.” Memories include the target information — what one is being asked to recall — and irrelevant information.
Reduced cognitive control can result in older adults having a harder time focusing on one piece of information because irrelevant information can be “stored in the same memory representation as the one that contains the target information,” Amer said. These distractions are bound to what the person is trying to remember and can ultimately impair memory if one is asked to recall something specific.
Amer illustrates it this way: A person knows several people named Mike, but they are trying to remember the last name of just one of the Mikes. As they think through all of the Mikes they know, they have to filter through everything they know about these people and suppress all the information related to the wrong Mikes. This internal navigation becomes especially difficult when one is older because it becomes more challenging to suppress irrelevant information.
This “interpretation [of the data] is sensible,” said André Fenton, a professor of neural science at New York University, who is not affiliated with the new paper. Fenton studies how brains store experiences as memories.
“We often think of distractions as coming from the outside, but there are distractions of internal origin,” Fenton said. “I would argue that internal distraction is far greater and always more challenging than external distraction.”
More research is needed to understand why reduced cognitive control can result in cluttering. One proposed explanation links back to the hippocampus, the complex brain structure that plays a significant role in learning and memory. It’s possible the hippocampus might be “indiscriminately forming these extra associations between all these pieces of information,” Amer said.
Generally, there’s also a need in memory and aging science to include more diverse populations into study samples, Ranganath said. For example, most research on older adults has been “based on samples of mostly white, highly educated, upper-middle-class individuals.” He thinks these findings would still hold up in a larger, more diverse study sample, but that research needs to happen to know definitely.
Meanwhile, memory cluttering isn’t entirely bad. While “cluttered” is the favored phrase in the paper, its authors write that the word could be substituted for “enriched” or “elaborated.” While the clutter of irrelevant information can make it more difficult to remember a specific detail, excessive knowledge can also help an individual in certain situations — such as when there’s a need to be creative, make a decision, or learn something new. These moments benefit from comprehensive knowledge.
In turn, it’s possible that the paradox of why older adults perform worse on most memory tests despite having more knowledge can be explained by something else: the tests themselves.
“There’s this prevalent idea in the literature that, as we age, we tend to perform worse on memory tests, which is true, but it’s also a result of the types of tests that we tend to use in the lab,” Amer said. “Those usually require a narrow focus of attention on one piece of information: You have to focus on the information, remember it, and then remember it again later on. Those are the types of tests that older adults don’t perform well on.”
But they perform better than younger adults on different types of tests — those that focus more on creativity and decision-making. This suggests the relationship between aging and performance should be viewed with more nuance, he said. Cognitive ability isn’t necessarily declining with age; it depends on the context.
“I think it just helps to know that, as we get older, we still have the capability to learn, but we’re not using it the right way,” Ranganath said. “When we see that we’re actually taking in lots of information, it helps to alleviate that feeling of helplessness and anxiety that we can feel when we can’t recall something. It changes the discussion from ‘aging sucks’ to ‘how can I keep my brain healthy as I get older?’”