Ageism impairs elders in many ways, but the most feared and insidious impairment involves the mind, not the body. As with many stereotypes, the notion of cognitive decline in late adulthood begins with a half-truth: Cognition does change in old age. But the fear is worse than the facts.

As at every earlier stage of development, losses and gains are evident. Ageism prevents people from seeing the gains. A realistic view notices both.

SLOWDOWN AND SHRINKAGE As humans age, connections between parts of the brain slow down. It takes longer, with age, to understand what is needed in a particular situation and then to respond. For instance, reading, conversation, and reflexes all take more time.

Senescence reduces the production of neurotransmitters—glutamate, acetylcholine, serotonin, and especially dopamine—that allow a nerve impulse to jump quickly across the synaptic gap from one neuron to another. Neural fluid decreases, myelination thins, and cerebral blood circulates more slowly. The result is an overall slowdown of the brain, evident in reaction time, movement, speech, and thought.

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Deterioration of cognition correlates with almost every motor slowdown. For example, gait speed predicts many measures of intellect (Hausdorff & Buchman, 2013). Walks slow? Talks slow? Oh no—thinks slow!

Brain size decreases with each passing year—less than 1 percent per year through most of adulthood but accelerating after age 60, such that a typical brain at age 80 is 20 percent smaller than at age 30 (Hedman et al., 2012).

The hippocampus (storing memories) and the prefrontal cortex (deciding and planning) shrink most. Cognitive reserve allows some brains to function well even in late, late adulthood; education is protective lifelong. However, neither of these completely compensates for brain senescence (Stern, 2013). No centenarian thinks as well as he or she did at age 30.

In every part of the brain, the volume of gray matter (crucial for processing new experiences) is reduced, in part because the cortex becomes thinner with every decade (Zhou et al., 2013). White matter generally is reduced as well, slowing the mind. However, white matter also increases in an odd way: Bright white spots appear on MRIs after age 50 or so.

These white matter lesions are thought to result from tiny impairments in blood flow. They increase the time it takes for a thought to be processed (Rodrigue & Kennedy, 2011). With age, transmission of impulses from regions of the brain, especially from parts of the cortex and the cerebellum, is disrupted. This correlates more with cognitive ability than with age (Bernard et al., 2013).

A comparative study finds that brain aging is similar in all primates, but humans experience losses relatively earlier than chimpanzees do—at the beginning of late adulthood instead of right before death (Xu Chen et al., 2013). That study’s authors speculate that medical measures have increased the life span, so the human brain survives longer than it was designed to do.

Evidence finds that older adults are as intellectually sharp as they always were on many tasks. However, with multitasking that requires younger adults to use all their cognitive resources, older adults are less proficient, perhaps because they already are using their brains to the max (Cappell et al., 2010). This is a loss but may also be a gain, if older adults no longer make the impulsive mistakes of the young.

Can anything compensate for brain losses in old age, to optimize thinking as people can optimize sex, or driving ability, or health? The answer is yes, sometimes. Brain plasticity occurs throughout life (e.g., Ram et al., 2011; Erickson et al., 2013). Medical research has not been able to stop cognitive aging directly, but protecting the body protects the brain. So cognition is aided if people exercise, eat well, and avoid most drugs (including cigarettes).

Furthermore, new neurons form and dendrites grow in adulthood. That surprised many scientists when it was first discovered. Almost everyone thought that humans never developed brain cells after infancy.

We now know that neurons appear in two specific areas, the olfactory region (smelling) and the hippocampus (remembering) (Surget et al., 2011). In addition, old neurons can develop new dendrites, allowing adults to resist depression and anxiety (Mateus-Pinheiro et al., 2013).

Although neurogenesis may occur in many living things, an evolutionary perspective suggests that humans may have had unique reasons to generate new neurons (Kempermann, 2012). When agriculture began (approximately 10,000 years ago), adults required more planning, remembering, and strategizing than before. Agriculture meant living in towns, not small nomadic clans, and that made human interaction more complex. Thus, “[m]oving actively in a changing world and dealing with novelty and complexity regulate adult neurogenesis. New neurons might thus provide the cognitive adaptability to conquer ecological niches rich with challenging stimuli” (Kempermann, 2012, p. 727).

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As you remember, Flynn found that the intellectual ability of each new cohort is better than that of the previous one. Perhaps the increasing complexity of modern life requires continuing improvement, with urbanization and globalization demanding intellectual expansion. If that is true, older people who continue to cope with challenges will continue to grow neurons.

PET and fMRI scans find that, compared with younger adults, older adults use more parts of their brains, including both hemispheres, to solve problems. This may be compensation: Using only one brain region may no longer be sufficient if that part has shrunk, so the older brain automatically activates more parts.

The positive finding that neurons are created is tempered by another finding—growth of the brain in late adulthood is slow and limited (S. Lee et al., 2012), and treatment for various illnesses, and general anesthesia for surgery, may kill neurons without creating new ones (Monje & Dietrich, 2012; Mashour & Avidan, 2013). The creation and growth of new neurons is less prolific than earlier in life, so it is not sufficient to restore the aging brain to its earlier state.

Health is crucial. Exercise, nutrition, and normal blood pressure are powerful influences on brain health, and these factors predict intelligence in old age. Some experts contend that with good health habits and favorable genes, no intellectual decrement will occur (Greenwood & Parasuraman, 2012).

Particular experiences may be important as well. One team recognizes “considerable heterogeneity in individual trajectories; whereas some persons decline rapidly, others exhibit slower decline, and still others remain stable or even improve as a result of practice and learning” (Boyle et al., 2013, p. 478).

Given the complexity, variation, and diversity of late-life cognition, we need to examine specifics to combat general stereotypes. For this purpose, the information-processing approach is useful, with details of input (sensing), memory (storage), programming (control), and output.

INPUT The first step in information processing is input, in which the brain receives information from the senses. No sense is as sharp at age 65 as at age 15. Glasses and hearing aids mitigate severe sensory losses, but subtle deficits impair cognition. Information must cross the sensory threshold—the divide between what is sensed and what is not—before a person can think about it.

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Older adults are less able to decipher the emotional content in speech, even when they hear the words correctly (Dupuis & Pichora-Fuller, 2010). They are also less able to see nuances of facial expression—a momentarily averted gaze, for instance. Further, it is harder to understand speech when vision is impaired (Tye--Murray et al., 2011), probably because watching lips and facial expressions aids understanding. Thus, small sensory losses—unnoticed but inevitable—impair cognition.

I know a father—not elderly but already with fading eyesight—who was scolding his 6-year-old daughter who was standing 10 feet away. Without his glasses, he did not see that her lip had started to quiver. He was startled when she cried; he did not realize how harsh his words seemed to her.

The cognition of almost 2,000 intellectually normal adults, average age 77, was repeatedly tested 5, 8, 10, and 11 years after the initial intake (Lin et al., 2013). At the 5-year retesting, an audiologist assessed their hearing. Between the start of the study and 11 years later, the average cognitive scores of the adults with hearing loss (who were often unaware of it) were down 7 percent, while those with normal hearing lost 5 percent.

That 2-percent difference seems small, but statistically it was highly significant (0.004). Greater hearing losses correlated with greater declines (Lin et al., 2013). Many other researchers likewise find that small input losses have a notable effect on output.

MEMORY If older people suspect memory loss, anxiety itself impairs their memory (Ossher et al., 2013). Worse than that, simply knowing that they are taking a memory test makes them feel years older (Hughes et al., 2013). Stereotype threat is powerful.

The more psychologists study memory, the more they realize that memory is not one function but many, each with a specific pattern. Some losses of the elderly are quite normal and others pathological (Markowitsch & Staniloiu, 2012). A person who cannot recall a word or a name is experiencing a normal loss of one aspect of memory; a person who cannot remember their city of birth has a pathological deficit.

Generally, explicit memory (recall of learned material) shows more loss than implicit memory (recognition and habits), which means that names are harder to remember than actions: Grandpa can still swim, ride a bike, and drive a car, even if he cannot name both current U.S. senators from his state. Memory tested individually typically shows declines, but memory as part of social learning is less likely to fade (Derksen et al., 2015).

One specific memory deficit is source amnesia—forgetting the origin of a fact, idea, or snippet of conversation. Source amnesia is particularly problematic in the twenty-first century, as video, audio, and print information bombards the mind.

In practical terms, source amnesia means that elders might believe a rumor or political advertisement because they forget the source. Compensation requires deliberate attention to the reason behind a message before accepting a con artist’s promises or the politics of a TV ad. However, elders are less likely than younger adults to analyze, or even notice, information surrounding the material they remember (Boywitt et al., 2012).

A hot political debate in the United States is about “dark money,” where by financial contributions to political candidates can be anonymous (Dawood, 2015). If dark money is banned, that will help younger voters make informed judgments, but older voters, with fragile source memory, may be less affected.

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Another crucial type of memory is called prospective memory—remembering to do something in the future (to take a pill, to meet someone for lunch, to buy milk). Prospective memory also fades notably with age (Kliegel et al., 2008). This loss becomes dangerous if, for instance, a person cooking dinner forgets to turn off the stove, or a person driving on the thruway is in the far lane when the exit appears.

One crucial aspect of prospective memory seems to be the ability to shift the mind quickly from one task to another: Older adults get immersed in one thought and have trouble changing gears (Schnitzspahn et al., 2013). For that reason, many elders follow routine sequences (brush teeth, take medicine, get the paper) and set an alarm to remind them to leave for a doctor’s appointment. (That is compensation.)

Working memory (remembering information for a moment before evaluating, calculating, and inferring its significance) also declines with age. Speed is critical: Older individuals take longer to perceive and process sensations, and that reduces working memory because some items fade before they can be considered (Stawski et al., 2013). Indeed, some experts think speed is the crucial variable that affects IQ over the years.

For example, a common test of IQ is to ask someone to repeat a string of digits just heard, but a slow-thinking person may be unable to process each number and then hold them all in memory. Speed of processing would explain why memory for vocabulary (especially recognition memory, not recall) is often unaffected by age. For instance, speed is irrelevant in knowing that chartreuse is a color, not an animal.

CONTROL PROCESSES Processing of information requires control processes, including selective attention, strategic judgment, and then appropriate action. Together these are the executive function of the brain, the work of the prefrontal cortex.

Each of these is theorized to slip in late adulthood. Crucial for paying attention is avoiding distractions and mind wandering. However, several studies report that the elderly are less likely to find their minds wandering than younger adults (Jackson & Balota, 2012; Frank et al., 2015).

Judgment, on the other hand, might be impaired. Instead of using analysis and forethought, the elderly tend to rely on prior knowledge, general principles, familiarity, and rules of thumb as they make decisions (Peters et al., 2011), basing actions on past experiences and current emotions.

For example, casinos have noticed that elderly gamblers gravitate to slot machines rather than to games requiring analysis. The reason, according to a study of brain scans of young and old slot players, is that the activated parts of older brains are less often the regions in which analysis occurs (McCarrey et al., 2012). When gamblers are able to analyze the odds, as younger players do, they spend less time with the slots.

One particular control process is development of strategies for retrieval. Some developmentalists believe that impaired retrieval is an underlying cause of intellectual lapses in old age because elders have many thoughts and memories that they cannot access. Since deep thinking requires recognizing and comparing the similarities and differences of experiences, if a person cannot retrieve memories of the past, new thinking is shallower than it might be.

Inadequate control processes may also explain why many older adults have extensive vocabularies (measured by written tests) but limited fluency (when they write or talk), why they are much better at recognition than recall, why tip-of-the-tongue forgetfulness is common, and why spelling is poorer than pronunciation.

Many gerontologists think elders would benefit by learning better control strategies. Unfortunately, even though “a high sense of control is associated with being happy, healthy, and wise,” many older adults resist suggested strategies because they believe that declines are “inevitable or irreversible” (Lachman et al., 2009, p. 144). Efforts to improve their use of control strategies are successful, but only when the strategy is explicitly taught (Murray et al., 2015; Brom & Kliegel, 2014; McDaniel & Bugg, 2012).

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OUTPUT The final step in information processing is output. In daily life, output is usually verbal. If the timbre and speed of a person’s speech sounds old, ageism might cause younger adults to dismiss the content without realizing that the substance may be profound. Then, if elders realize that what they say is ignored, they talk less, and output is diminished. Mutual respect is crucial.

Scientists usually measure output through use of standardized tests of mental ability. As already noted, if older adults think their memory is being tested, that alone impairs them (Hughes et al., 2013). Even without stereotype threat, output on cognitive tests may not reflect ability, as you will now see.

Measurement of ability needs to take into account the age and the needs of the person. For example, older adults are at their best in the early morning, when adolescents are half asleep. If both age groups are tested at the same time of day, that would be unfair for either the old or the young.

Similarly, if intellectual ability were to be assessed via a timed test, then faster thinkers (usually young) would score higher than slower thinkers (usually old), even if the slower ones would excel after a few more seconds to think. Further, some places—e.g., a college laboratory—would be more familiar to emerging adults than to older ones, and that might affect results.

These are some reasons that certain age differences in prospective memory appear in laboratory tests but disappear in naturalistic settings, a phenomenon called the “age-prospective memory-paradox” (Schnitzspahn et al., 2011). Motivation seems crucial; elders may remember whatever they believe is important—phoning grandchildren on their birthday, for instance—but not care about repeating a series of disconnected words (a common test of memory).

A focus on what elders actually need and want to remember is called ecological validity. Results of research that takes context and circumstances into account finds that elders have far better memories than ageist predictions and measurements find.

Again, good news must be tempered: “There is no objective way to evaluate the degree of ecological validity . . . because ecological validity is a subjective concept” (Salthouse, 2010, p. 77). It is impossible to be totally objective in assessing memory.

The final ecological question is, “What is memory for?” Fear of memory loss is more typical at age 60 than at age 80. Unless they develop a brain condition such as Alzheimer’s disease (soon described), elders remember how to live their daily lives. Is that enough?