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New research says older people are slow on memory tests because they have more mental data to search for the answer.


An Aging Brain Is Still Pretty Smart

It may be slower, but it has a wealth of information to draw from.

A few years ago, Michael Ramscar, a linguistics researcher at the University of Tübingen in Germany, came across a paper saying that cognitive decline starts as early as age 45. He was 45 himself and felt he hadn't yet peaked. He remembers thinking: "That doesn't make sense to me; 99 percent of the people I look up to intellectually, who keep me on my mettle, are older than I am."

The paper concluded that a person's vocabulary declines after age 45, and that finding really made no sense to him. The researchers were trying to measure how quickly people remembered words, he says, without even considering the quantity of words they had stored in memory.

Ramscar began to wonder who has the better memory: the young person who knows a little and remembers all of it, or the older person who has learned a lot and forgets a little of it?

His research, published in the January 2014 issue of Topics in Cognitive Science, argues that studies on memory ask the wrong questions. It could be that older, wiser heads are so chock full of knowledge that it simply takes longer to retrieve the right bits. (It's important to note that the research is aimed at healthy, aging brains, not those afflicted with Alzheimer's disease or other forms of dementia, which rob the brain of memory and other abilities.)

Many memory tests might ask a 20-year-old and a 70-year-old to memorize a list of items, then recall them. The tests don't address the size and content of each subject's existing memory. So Ramscar created computer models simulating young brains and older brains. He fed information into both models but added buckets more information to the model meant to simulate an older brain.

"I could see precious little evidence of decline in [the models of] healthy, older people," he says. "Their slowness and slight forgetfulness were exactly what I'd expect" because with more to draw on, there are more places to search, and there's more information to search through to find an answer.

Both Fuller and Slower

There's no denying that older people have acquired more experience and information than younger people, says Denise Park, co-director of the Center for Vital Longevity at the University of Texas at Dallas, whose research focuses on how the mind changes and adapts as people age. "As we age we accrue knowledge, have a higher vocabulary score, and know more about the world," says Park. "There's a reason we don't have 20-year-olds running the world."

She sees the value of Ramscar's research but also believes there's no denying that the brain deteriorates with age just as every other body part does.

Rather than the brain being slower just because it contains so much information, it is also slowing down from simple aging, she said. Imaging studies show clearly that even healthy aging brains show signs of shrinkage in areas concerned with learning, reason, and memory. At the same time, the greater store of knowledge helps older brains compensate.

So it could be that a couple of things are going on at the same time: The aging brain is accumulating knowledge, kind of like a library full of dusty volumes. And because it is deteriorating like any other body part, it operates more slowly.

So Park believes that we forget more as we get older, and we compensate for that memory loss by being able to draw on a bigger pool of stored knowledge. "It may be true that knowledge slows down the system, but that doesn't mean that the system, as it ages, doesn't also operate more slowly," says Park. "I would argue that the amount of knowledge allows us to compensate for the slowdown."

Her conclusion: "I strongly believe that our everyday performance does not decline with age." That's because as the ability to retrieve memories quickly declines, the brain is still building up stores of knowledge from which to draw.

Storage Space

In the long run, Ramscar hopes his research, which he discusses on his blog, can help define normal patterns of aging, and that older people can begin to think about what is happening to their brains as something other than "a decline."

If only we could do as Sherlock Holmes did: He allowed only pertinent clues, like shed hairs or scratched doorjambs, to find a home in his brain. When his colleague Dr. Watson told him, in A Study in Scarlet, that the Earth revolved around the sun, Holmes dismissed the information as unworthy of storage space: "Depend upon it there comes a time when for every addition of knowledge you forget something that you knew before."