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Edited by: Wayne D. Gray
Online ISSN: 1756-8765
Published on behalf of Cognitive Science Society
Impact Factor: 2.284

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Medicine & Healthcare, Psychology


January 21, 2014

Rethinking Aging: Older Brains Slower Due to Greater Experience, Rather than Cognitive Decline

What happens to our cognitive abilities as we age? If you think the answer involves a steady deterioration of brain function, research reported this week in Topics in Cognitive Science may cause you to think again. The work, spearheaded by Dr. Michael Ramscar of the University of Tuebingen, takes a critical look at the measures that are usually thought to show that our cognitive abilities decline across adulthood: Instead of finding evidence of decline, the team discovered that most standard cognitive measures, which date back to the early 20th Century, are flawed, confusing increased knowledge for declining capacity.

The Tuebingen study uses the same Big Data techniques that have been quietly revolutionizing our on-line experience to build computer models that simulate human performance in cognitive testing. Computers were trained as though they were humans, reading a certain amount each day, and learning new things along the way. When the researchers let a computer “read” only so much, its performance on cognitive tests resembled that of a young adult. But if the same computer was exposed to the experiences we might encounter over a lifetime—with reading simulated over decades—its performance now looked like that of an older adult. Often it was slower, but not because its processing capacity had declined. Rather, just as it takes longer to find a missing sock as a drawer gets bigger, increased “experience” had caused the computer’s database to grow, giving it more data to process—and that processing takes time.

What does this finding mean for our understanding of our ageing minds, for example older adults’ increased difficulties with word recall? These are traditionally thought to reveal how our memory for words deteriorates with age, but Big Data adds a twist to this idea. Technology now allows researchers to make quantitative estimates of the number of words an adult can be expected to learn across a lifetime, enabling the Tuebingen team to separate the challenge that increasing knowledge poses to memory from the actual performance of memory itself. “Imagine someone who knows two people’s birthdays and can recall them almost perfectly. Would you really want to say that person has a better memory than a person who knows the birthdays of 2000 people, but can ‘only’ match the right person to the right birthday nine times out of ten?” asks Ramscar.

Computationally, at least, the team show how the answer to this philosophical conundrum is, “no.” When Ramscar and colleagues trained their computer models on huge linguistic datasets, they found that standardized vocabulary tests, which are used to take account of the growth of knowledge in studies of ageing, massively underestimate the size of adult vocabularies. It takes computers longer to search databases of words as their sizes grow, an unsurprising fact that may have important implication for our understanding of age-related slowdowns and decline. Because the Tuebingen team discovered that to get their computers to replicate human performance in word recognition tests across adulthood, they had to keep their capacities the same. “Forget about forgetting,” explained Tuebingen researcher Peter Hendrix, “if I wanted to get the computer to look like an older adult, I had to keep all the words it learned in memory and let them compete for attention.”

The research shows that studies of the problems older people have with recalling names suffer from a similar blind spot: These days people name their children in very different ways to their grandparents. This cultural shift toward greater name diversity has led to a massive proliferation in the number of names we give to our children, meaning the number of different names anyone learns over their lifetime has increased dramatically. The work shows how this makes locating a name in memory far harder than it has ever been before. Even for computers.

Ramscar and colleagues’ work provides more than an explanation of why, in the light of all the extra information they have to process, we might expect older brains to seem slower and more forgetful than younger brains. Their work also shows how changes in test performance that have been taken as evidence for declining cognitive abilities in fact demonstrates older adults’ greater mastery of the knowledge they have acquired.

"Take paired-associate learning,” a commonly used cognitive test that involves learning to connect words like “up” to “down” or “necktie” to “cracker” in memory. Using Big Data sets to quantify how often different words appear together in English, the Tuebingen team show that younger adults do better when asked to learn to pair “up” with “down” than “necktie” and “cracker” because “up” and “down” appear in close proximity to one another more frequently. However, whereas older adults also understand which words don’t usually go together, young adults notice this less. When the researchers examined performance on this test across a range of word pairs that go together more and less in English, they found older adult’s scores to be far more closely attuned to the actual information in hundreds of millions of words of English than their younger counterparts.

As Prof. Harald Baayen, who heads the Alexander von Humboldt Quantitative Linguistics research group where the work was carried out puts it,  “If you think linguistic skill involves something like being able to choose one word given another, younger adults seem to do better in this task. But, of course, proper understanding of language involves more than this. You have also to not put plausible but wrong pairs of words together. The fact that older adults find nonsense pairs – but not connected pairs – harder to learn than young adults simply demonstrates older adults’ much better understanding of language. They have to make more of an effort to learn unrelated word pairs because, unlike the youngsters, they know a lot about which words don’t belong together.”

Our planet is now home to more elderly people than at any time in human history, but beliefs about their declining cognitive abilities often mean that older adults are seen as a burden on society. Yet, as the Tuebingen researchers note, it is impossible to tell if the mind’s information processing capacities do in fact decline with age if you don’t measure the information the mind processes, or how it changes over time. In every one of the cognitive tests in which the team measured this information, no evidence of any change in our minds’ processing capacities was found. The researchers simply found that the tests required older adults to make more effort as they sorted through the larger stores of knowledge they had acquired from experience.

Commenting on these findings in an editorial in the Journal Topics in Cognitive Science, Editors Wayne Gray and Thomas Hills suggest, “It is time we rethink what we mean by the aging mind before our false assumptions result in decisions and policies that marginalize the old or waste precious public resources to remediate problems that do not exist.”