The Older Mind May Not Be Failing; It May Just Be Fuller
老年記憶衰退，還是記太多了？
By Benedict Carey

Most 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.
多數到了某個年紀的人（我們明白自己屬於哪一類），都不願花太多休閒時間檢視探討認知能力與年齡的研究結果。事實相當殘酷，且舉一例：記憶的速度與正確性從25歲前後開始衰減不止。

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 psychology.
對每個年逾50，終於懂得徹底活在當下、卻發現可能時不我予者，這事實也都很熟悉。腦力隨年齡衰退是心理學最確鑿的發現之一。

Over the years, some scientists have questioned this dotage curve. But these challenges have had an ornery-old-person slant: that the tests were biased toward the young, for example. Or that older people have learned not to care about clearly trivial things, like memory tests. Or that an older mind must organize information differently from one attached to some 22-year-old who records his every move on Instagram.
多年來一直有科學家挑戰這記憶老化曲線，但都有個頑固的偏見：如強調測驗都對年輕人有利；或老人知道不必太在意記憶測驗之類瑣事，或者主張老年人思考時組織資訊的方式，必不同於把每個動作都用數位照相軟體記下的22歲年輕人。

Now comes a new kind of challenge to the evidence of a cognitive decline, from a decidedly digital quarter: data mining, based on theories of information processing. In a paper published in Topics in Cognitive Science, linguistic researchers from the University of Tübingen in Germany used advanced learning models to search enormous databases of words and phrases.
現在又有研究從重要的數位角度，依資訊處理理論提出的「資料探勘」主張對認知減退的證據提出新挑戰。認知科學專題期刊一報告指出，德國杜賓根大學語言學者以先進學習模型研究龐大字詞資料庫。

Since educated older people generally know more words than younger people, 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” disappeared.
受過教育的老年人通常比年輕人認識更多字，實驗便以老年人頭腦如何才能找到一個字來進行模擬。把這項差異置入研究模型時，老人泰半年齡「弱勢」便告消失。

“What shocked me, to be honest, is that for the first half of the time we were doing this project, I totally bought into the idea of age-related cognitive decline in healthy adults,” the lead author, Michael Ramscar, said by email. But the simulations, he added, “fit so well to human data that it slowly forced me to entertain this idea that I didn’t need to invoke decline at all.”
研究領導人南斯卡在電郵中說：「老實說，令我震撼的是進行研究的前半段時，我完全相信健康成人的年齡與認知減退有關。但這項模擬與人們的資料如此契合，逐漸使我不得不同意，我完全不必強調認知減退的問題。」

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.
神經科學家表示，新研究不太可能推翻百年來的研究結果。神經科學家有理由相信神經的處理速度一如多種反射運動，會隨年齡減緩；解剖學研究也指出腦部會有微妙的結構改變，可能影響記憶。

Still, the new report will most probably add to a growing skepticism about how steep age-related decline really is. Many studies comparing older and younger people, did not for example, take into account the effects of pre-symptomatic Alzheimer’s disease, said Laura Carstensen, a psychologist at Stanford University in California.
但這份報告幾乎必然會讓一些人更加懷疑年齡與記憶減退究竟有多大關係。加州史丹福大學心理學者蘿拉．卡斯丹森表示，例如，許多老年人與年輕人記憶力的比較研究，並未考慮阿茲海默症前期症狀對記憶的影響。

Dr. Carstensen and others have found, too, that with age people become biased in their memory toward words and associations that have a positive connotation. This bias very likely applies when older people perform so-called paired-associate tests, a common measure that involves memorizing random word pairs, like ostrich and house.
卡斯丹森等人還發現，隨年齡增長人們會偏好記住具正面意義的文字和聯想。當老年人在做「配對聯想測驗（對字偶進行隨機記憶的一種常用評量方式），例如鴕鳥與房子」時，極可能出現這種偏好。

“Given that most cognitive research asks participants to engage with neutral (and in emotion studies, negative) stimuli, the traditional research paradigm may put older people at a disadvantage,” Dr. Carstensen said.
她說，「多數認知研究都要求給予參與者中性的刺激（情緒性研究則給予負面刺激），這種傳統研究典範可能對老人不利。」

The new data-mining analysis also raises questions about many of the measures scientists use. 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.
新的資料探勘分析也對科學家許多評量標準提出質疑。南斯卡博士與研究夥伴應用先進的學習模型，拿兩組經過評估的字詞來做研究，分別為70歲與20歲受過教育者看過的字。他說，做「配對─聯想測驗」時，他們的模型對於老人與年輕人的分數差異，具有75%的解釋能力。

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).
這表示腦袋存放的字詞越多，通常也得花更長的時間才能找到特定的字（或字偶）。

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.
研究思考與記憶的科學家常把「流質（可變）」與「晶質（固化）」智力做明顯區分。前者包括短期記憶（記住電話號碼）、分析推理，並能對不相干的言辭（如一些場面話）置之不理。後者則是累積學問、字彙及專業知識。

“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. In a variety of experiments, Dr. Hambrick and Timothy A. Salthouse of the University of Virginia have shown that crystallized knowledge climbs sharply between ages 20 and 50 and then plateaus, even as the fluid kind (like analytical reasoning) is dropping steadily – by more than 50 percent between ages 20 and 70 in some studies.
密西根州大心理學者韓布里克表示，「事實上南斯卡團隊所主張的是，晶質智力提昇可彌補流質智力的減退。」他與維吉尼亞大學的索豪斯透過多項實驗顯示，晶質智力在20-50歲間大幅提昇，然後達到高原期，同時期流質智力 （如分析推理）則持續下降；一些研究顯示20-70歲間流質智力減幅超過50%。

Dr. Ramscar’s report was a simulation and included no tested subjects, though he said he does have several memory studies with normal subjects on the way.
南斯卡的報告是一項模擬，不含任何檢驗主題，不過他表示正在準備數項有正規主題的記憶研究。

For now, this new digital-era challenge to “cognitive decline” can serve as a ready-made explanation for blank moments.
目前，這項對「認知減退」的數位時代新挑戰，可以充當對於記憶空白現成的解釋。

It’s not that you’re slow. It’s that you know so much.
不是你的記性遲鈍了，是你知道的東西太多了。

原文參照：
http://newoldage.blogs.nytimes.com/2014/01/27/the-older-mind-may-just-be-a-fuller-mind/

2014-02-18聯合報/G9版/UNITEDDAILYNEWS 任中原譯 原文參見紐時週報十一版上