Seeing the glass as half full: Taking a new look at cognition and aging 11-12

Image credit : Shyam's Imagination Library

From a cognitive perspective, aging is typically associated with decline. As we age, it may get harder to remember names and dates, and it may take us longer to come up with the right answer to a question.

But the news isn’t all bad when it comes to cognitive aging, according to a set of three articles in the July 2014 issue of Perspectives in Psychological Science.

Plumbing the depths of the available scientific literature, the authors of the three articles show how several factors — including motivation and crystallized knowledge — can play important roles in supporting and maintaining cognitive function in the decades past middle age.

Motivation Matters

Lab data offer evidence of age-related declines in cognitive function, but many older adults appear to function quite well in their everyday lives. Psychological scientist Thomas Hess of North Carolina State University sets forth a motivational framework of “selective engagement” to explain this apparent contradiction.

If the cognitive cost of engaging in difficult tasks increases as we age, older adults may be less motivated to expend limited cognitive resources on difficult tasks or on tasks that are not personally relevant to them. This selectivity, Hess argues, may allow older adults to improve performance on the tasks they do choose to engage in, thereby helping to account for inconsistencies between lab-based and real-world data.

Prior Knowledge Brings Both Costs and Benefits

Episodic memory – memory for the events of our day-to-day lives – seems to decline with age, while memory for general knowledge does not. Researchers Sharda Umanath and Elizabeth Marsh of Duke University review evidence suggesting that older adults use prior knowledge to fill in gaps caused by failures of episodic memory, in ways that can both hurt and help overall cognitive performance. While reliance on prior knowledge can make it difficult to inhibit past information when learning new information, it can also make older adults more resistant to learning new erroneous information.

According to Umanath and Marsh, future research should focus on better understanding this compensatory mechanism and whether it can be harnessed in developing cognitive interventions and tools.

Older Adults Aren’t Necessarily Besieged By Fraud

Popular writers and academics alike often argue that older adults, due to certain cognitive differences, are especially susceptible to consumer fraud. Psychological scientists Michael Ross, Igor Grossmann, and Emily Schryer of the University of Waterloo in Canada review the available data to examine whether incidences of consumer fraud are actually higher among older adults. While there isn’t much research that directly answers this question, the research that does exist suggests that older adults may be less frequent victims than other age groups.

Ross, Grossmann, and Schryer find no evidence that older adults are actually more vulnerable to fraud, and they argue that anti-fraud policies should be aimed at protecting consumers of all ages.

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It’s Not a ‘Stream’ of Consciousness 05-11

It’s Not a ‘Stream’ of Consciousness 

IN 1890, the American psychologist William James famously likened our conscious experience to the flow of a stream. “A ‘river’ or a ‘stream’ are the metaphors by which it is most naturally described,” he wrote. “In talking of it hereafter, let’s call it the stream of thought, consciousness, or subjective life.”

While there is no disputing the aptness of this metaphor in capturing our subjective experience of the world, recent research has shown that the “stream” of consciousness is, in fact, an illusion. We actually perceive the world in rhythmic pulses rather than as a continuous flow.

Some of the first hints of this new understanding came as early as the 1920s, when physiologists discovered brain waves: rhythmic electrical currents measurable on the surface of the scalp by means of electroencephalography. Subsequent research cataloged a spectrum of such rhythms (alpha waves, delta waves and so on) that correlated with various mental states, such as calm alertness and deep sleep.

Researchers also found that the properties of these rhythms varied with perceptual or cognitive events. The phase and amplitude of your brain waves, for example, might change if you saw or heard something, or if you increased your concentration on something, or if you shifted your attention.

But those early discoveries themselves did not change scientific thinking about the stream-like nature of conscious perception. Instead, brain waves were largely viewed as a tool for indexing mental experience, much like the waves that a ship generates in the water can be used to index the ship’s size and motion (e.g., the bigger the waves, the bigger the ship).

Recently, however, scientists have flipped this thinking on its head. We are exploring the possibility that brain rhythms are not merely a reflection of mental activity but a cause of it, helping shape perception, movement, memory and even consciousness itself.

What this means is that the brain samples the world in rhythmic pulses, perhaps even discrete time chunks, much like the individual frames of a movie. From the brain’s perspective, experience is not continuous but quantized.

Another clue that led to this discovery was the so-called wagon-wheel illusion, in which the spokes on a wheel are sometimes perceived to reverse the direction of their rotation. This illusion is easy to induce with a strobe light if the rotation of the wheel is such that each strobe flash captures the spoke location slightly behind the location captured on the previous flash, leading to the perception of reverse motion. The illusion results from “sampling” the scene in discrete frames or time chunks.

The telling fact, for perceptual scientists, is that this illusion can also occur during normal observation of a rotating wheel, in full daylight. This suggests that the brain itself, even in the absence of a strobe light, is sampling the world in discrete chunks.

Scientists have uncovered still more clues. It turns out, for example, that our ability to detect a subtle event, like a slight change in a visual scene, oscillates over time, cycling between better and worse perceptual sensitivity several times a second. Research shows that these rhythms correlate with electrical rhythms of the brain.


Consider a study that I conducted with my colleagues, forthcoming in the journal Psychological Science. We presented listeners with a three-beat-per-second rhythm (a pulsing “whoosh” sound) for only a few seconds and then asked the listeners to try to detect a faint tone immediately afterward. The tone was presented at a range of delays between zero and 1.4 seconds after the rhythm ended. Not only did we find that the ability to detect the tone varied over time by up to 25 percent — that’s a lot — but it did so precisely in sync with the previously heard three-beat-per-second rhythm.

Why would the brain do this? One theory is that it’s the brain’s way of focusing attention. Picture a noisy cafe filled with voices, clanging dishes and background music. As you attend to one particular acoustic stream — say, your lunch mate’s voice — your brain synchronizes its rhythm to the rhythm of the voice and enhances the perceptibility of that stream, while suppressing other streams, which have their own, different rhythms. (More broadly, this kind of synchronization has been proposed as a mechanism for communication between neural networks within the brain.)

All of this points to the need for a new metaphor. We should talk of the “rhythm” of thought, of perception, of consciousness. Conceptualizing our mental experience this way is not only more accurate, but it also situates our mind within the broader context of the daily, monthly and yearly rhythms that dominate our lives.

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The Rise and Fall of Cognitive Skills 03-10

The Rise and Fall of Cognitive Skills

Neuroscientists find that different parts of the brain work best at different ages.

Scientists have long known that our ability to think quickly and recall information, also known as fluid intelligence, peaks around age 20 and then begins a slow decline. However, more recent findings, including a new study from neuroscientists at MIT and Massachusetts General Hospital (MGH), suggest that the real picture is much more complex.

The study, which appears in the journal Psychological Science, finds that different components of fluid intelligence peak at different ages, some as late as age 40.

“At any given age, you’re getting better at some things, you’re getting worse at some other things, and you’re at a plateau at some other things. There’s probably not one age at which you’re peak on most things, much less all of them,” says Joshua Hartshorne, a postdoc in MIT’s Department of Brain and Cognitive Sciences and one of the paper’s authors.

“It paints a different picture of the way we change over the lifespan than psychology and neuroscience have traditionally painted,” adds Laura Germine, a postdoc in psychiatric and neurodevelopmental genetics at MGH and the paper’s other author.

Measuring peaks

Until now, it has been difficult to study how cognitive skills change over time because of the challenge of getting large numbers of people older than college students and younger than 65 to come to a psychology laboratory to participate in experiments. Hartshorne and Germine were able to take a broader look at aging and cognition because they have been running large-scale experiments on the Internet, where people of any age can become research subjects.

Their web sites, gameswithwords.org and testmybrain.org, feature cognitive tests designed to be completed in just a few minutes. Through these sites, the researchers have accumulated data from nearly 3 million people in the past several years.

In 2011, Germine published a study showing that the ability to recognize faces improves until the early 30s before gradually starting to decline. This finding did not fit into the theory that fluid intelligence peaks in late adolescence. Around the same time, Hartshorne found that subjects’ performance on a visual short-term memory task also peaked in the early 30s.

Intrigued by these results, the researchers, then graduate students at Harvard University, decided that they needed to explore a different source of data, in case some aspect of collecting data on the Internet was skewing the results. They dug out sets of data, collected decades ago, on adult performance at different ages on the Weschler Adult Intelligence Scale, which is used to measure IQ, and the Weschler Memory Scale. Together, these tests measure about 30 different subsets of intelligence, such as digit memorization, visual search, and assembling puzzles.

Hartshorne and Germine developed a new way to analyze the data that allowed them to compare the age peaks for each task. “We were mapping when these cognitive abilities were peaking, and we saw there was no single peak for all abilities. The peaks were all over the place,” Hartshorne says. “This was the smoking gun.”

However, the dataset was not as large as the researchers would have liked, so they decided to test several of the same cognitive skills with their larger pools of Internet study participants. For the Internet study, the researchers chose four tasks that peaked at different ages, based on the data from the Weschler tests. They also included a test of the ability to perceive others’ emotional state, which is not measured by the Weschler tests.

The researchers gathered data from nearly 50,000 subjects and found a very clear picture showing that each cognitive skill they were testing peaked at a different age. For example, raw speed in processing information appears to peak around age 18 or 19, then immediately starts to decline. Meanwhile, short-term memory continues to improve until around age 25, when it levels off and then begins to drop around age 35.

For the ability to evaluate other people’s emotional states, the peak occurred much later, in the 40s or 50s.

Christopher Chabris, an associate professor of psychology at Union College, said a key feature of the study’s success was the researchers’ ability to gather and analyze so much data, which is unusual in cognitive psychology.

“You need to look at a lot of people to discover these patterns,” says Chabris, who was not part of the research team. “They’re taking the next step and showing a more fine-grained picture of how cognitive abilities differ from one another and the way they change over time.”

More work will be needed to reveal why each of these skills peaks at different times, the researchers say. However, previous studies have hinted that genetic changes or changes in brain structure may play a role.

Researchers have been running large-scale experiments on the Internet, where people of any age can become research subjects. Their websites feature cognitive tests designed to be completed in just a few minutes. Shown here is a “pattern completion test” from their website, testmybrain.org. Image credit: Jose-Luis Olivares/MIT (with image courtesy of the researchers).

“If you go into the data on gene expression or brain structure at different ages, you see these lifespan patterns that we don’t know what to make of. The brain seems to continue to change in dynamic ways through early adulthood and middle age,” Germine says. “The question is: What does it mean? How does it map onto the way you function in the world, or the way you think, or the way you change as you age?”

Accumulated intelligence

The researchers also included a vocabulary test, which serves as a measure of what is known as crystallized intelligence — the accumulation of facts and knowledge. These results confirmed that crystallized intelligence peaks later in life, as previously believed, but the researchers also found something unexpected: While data from the Weschler IQ tests suggested that vocabulary peaks in the late 40s, the new data showed a later peak, in the late 60s or early 70s.

The researchers believe this may be a result of better education, more people having jobs that require a lot of reading, and more opportunities for intellectual stimulation for older people.

Hartshorne and Germine are now gathering more data from their websites and have added new cognitive tasks designed to evaluate social and emotional intelligence, language skills, and executive function. They are also working on making their data public so that other researchers can access it and perform other types of studies and analyses.

“We took the existing theories that were out there and showed that they’re all wrong. The question now is: What is the right one? To get to that answer, we’re going to need to run a lot more studies and collect a lot more data,” Hartshorne says.

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