People of a certain age (and we know who we are) don’t spend much leisure time reviewing the research into cognitive performance and aging. The story is grim, for one thing: Memory’s speed and accuracy begin to slip around age 25 and keep on slipping.
The story is familiar, too, for anyone who is over 50 and, having finally learned to live fully in the moment, discovers it’s a senior moment. The finding that the brain slows with age is one of the strongest in all of psychology.
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Since educated older people generally know more words than younger people, simply by virtue of having been around longer, the experiment simulates what an older brain has to do to retrieve a word. And when the researchers incorporated that difference into the models, the aging “deficits” largely disappeared.
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In fact, the new study is not likely to overturn 100 years of research, cognitive scientists say. Neuroscientists have some reason to believe that neural processing speed, like many reflexes, slows over the years; anatomical studies suggest that the brain also undergoes subtle structural changes that could affect memory.
Still, the new report will very likely add to a growing skepticism about how steep age-related decline really is.
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Dr. Ramscar and his colleagues applied leading learning models to an estimated pool of words and phrases that an educated 70-year-old would have seen, and another pool suitable for an educated 20-year-old. Their model accounted for more than 75 percent of the difference in scores between older and younger adults on items in a paired-associate test, he said.
That is to say, the larger the library you have in your head, the longer it usually takes to find a particular word (or pair).
Scientists who study thinking and memory often make a broad distinction between “fluid” and “crystallized” intelligence. The former includes short-term memory, like holding a phone number in mind, analytical reasoning, and the ability to tune out distractions, like ambient conversation. The latter is accumulated knowledge, vocabulary and expertise.
“In essence, what Ramscar’s group is arguing is that an increase in crystallized intelligence can account for a decrease in fluid intelligence,” said Zach Hambrick, a psychologist at Michigan State University.
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For the time being, this new digital-era challenge to “cognitive decline” can serve as a ready-made explanation for blank moments, whether senior or otherwise.
It’s not that you’re slow. It’s that you know so much.