In common with every other creature, humans show diminished physical and cognitive functioning as they age; accompanied by losses in brain, bone, and muscle, senescence is a normal part of aging.1 Despite losses in mental functioning across a variety of domains,2 mental content, such as vocabulary, often remains intact or even grows into late adulthood.3 Most societies regard age as a source of wisdom, suggesting an improvement in the quality of our judgment.4 We are hardly unique in this regard—elephants choose the oldest female in their group as a leader5—but the exaggerated role of learning in humans enhances the effect of age on wisdom.
Deficits in some areas caused by biological senescence may be offset by gains due to increased knowledge and wisdom.6 Members of all cultures and countries, ethnic and religious groups, and social classes experience these deficits and gains, but the degree to which an individual does so varies wildly. Some people show remarkable resilience to functional cognitive losses while others remain youthful and energetic when quite old. But even the most resilient decline with age. Just as there are no eighty-year-olds who could be mistaken for a twenty-year-old, there are no eighty-year-old brains that could be confused with a twenty-year-old brain. There are no eighty-year-old minds as quick and agile as they were at twenty.
In Decline
Senescence and its associated deficits have long been the subject of research. The applied value of this work is entirely a function of the type of answers it uncovers. If research reveals that resilience to aging is genetic, this is of no use to anyone—for the time being, at least. Not so if resilience is a product of psychology or diet. For obvious reasons, many researchers pursue leads that suggest the effects of aging can be ameliorated through treatment.
In the mid-1990s, I attended a colloquium by Lynn Hasher on aging and memory. She argued that age-related memory problems are caused by difficulties inhibiting irrelevant memories. Such difficulties, she argued further, are a normal part of aging accompanying the atrophy of the frontal lobes. Given that many social situations require us to inhibit our initial reactions, it occurred to me that older adults might experience social problems as a consequence of inhibitory failure. Older Americans, for example, often appear more prejudiced than their younger counterparts.7 Social norms during the periods in which generations come of age have been seen as a cause.
Hasher’s research raises the possibility that this explanation might be only part of the story. Automatic stereotypic thoughts are common in most people,8 and perhaps inhibition of these thoughts becomes a particular problem among older adults. Several studies, including my own, have found evidence to support the idea that increased prejudice among older adults is caused by inhibitory losses,9 and that such losses can lead to other social problems.10
When I began presenting this research at conferences, social psychologists showed interest in the findings, but geropsychologists were often uninterested, or even hostile. As one audience member put it, “It sounds like you’re a declinist.” This was, in fact, precisely what I was suggesting: aging leads to decline. When I submitted a paper describing these findings, one of the reviewers wrote: “Although there is something intriguing about the idea that declines in executive function could negatively impact social functioning, the more interesting question may be why they do not.”
This is wishful thinking.
Attitude in Aging
Different individuals age differently. Some older adults show major losses in function, while others show only mild deficits.11 In some cases, cognitive losses can be seen that mirror the degree of brain atrophy visible in MRI scans, while in other cases, people remain mentally robust in the face of substantial physical losses.12 These differences, which are only loosely correlated with the underlying biological substrate, are suggestive of an important role for attitudes and behaviors in the effects of aging.
There is increasing evidence that physical and mental exercise can delay and even reverse some aspects of cognitive decline. Sedentary older adults who take up a program of aerobic exercise show enhanced functioning in the frontal lobes of their brains and experience gains in memory and attention.13 Research also indicates that people who spend a great deal of time engaged in complex thought are able to delay the onset of cognitive decline. Complex thought is measured as the amount of time devoted to formal education, the mental requirements of work, and leisure activities requiring deep thought. The latter need not involve a difficult task in mathematics or challenging mental game—navigating complex social relationships is all it takes.14 These activities play a demonstrable role in the delayed onset of cognitive decline.15
Complex thought is believed to enhance the brain’s wiring by causing it to form more and better connections. In 1949, Donald Hebb proposed that when neurons fire and the connecting neurons do not respond, the connection between the two is weakened, and vice versa.16 When the brain suffers physical degradation later in life, brains with stronger connections are better able to withstand losses before functional deficits emerge.
People who have positive expectations of aging may be more likely to engage in complex thought late in life, which might, in turn, delay cognitive decline. Becca Levy has conducted a series of longitudinal studies examining whether people’s attitudes toward aging when they were young or middle-aged adults is predictive of health outcomes much later in life. Levy found that people who held positive views of aging exhibit decreased biomarkers of stress, such as cortisol17 and inflammation,18 and longer telomeres after significant life stressors, such as military combat or a heart attack.19
Consistent with these signs of reduced stress, people who had positive views of aging earlier in life go on to experience fewer cardiovascular events,20 a reduced likelihood of Alzheimer’s disease,21 and live an average of seven and a half years longer than those who held negative views.22 These studies have been supplemented by experiments in which older adults are subtly primed to think of themselves in terms of positive or negative aspects of aging. Similar effects to the longitudinal studies have been observed.23
These results are striking. Beliefs about aging held at thirty or forty years of age may well predict cognitive and physical functioning in later life. But this does not mean that they play any sort of causal role. Genetic robustness and resilience to aging amongst a person’s parents and grandparents could lead even a very young person to develop a positive attitude toward aging.
In light of our limited knowledge of the genetics of aging, the sources of these beliefs must be examined more thoroughly. Concurrent indicators of health and well-being are typically used as control measures, but the aging trajectories of the participants’ parents and grandparents should also be considered. A person who is genetically robust to aging might be in relatively poor health in middle age but then show little decline over time, and vice versa. If beliefs actually predicted functional decline, above and beyond the genetic components of senescence, we would have much better evidence that positive self-fulfilling prophecies make people robust to senescence. In the absence of controls for the sources of beliefs about aging—and ideally the underlying genetics—it is impossible to know whether the predictive power of positive attitudes means anything at all.
The impact of attitudes and beliefs can, of course, be negative as well as positive. Research in this area has focused on stereotype threat.24 For domains in which people are seen as being stereotypically incompetent, it has been shown that they perform more poorly if they believe their evaluators hold such stereotypes. Older adults are susceptible to such effects, and display deficits in memory and other cognitive processes when they feel they are being negatively stereotyped.25 Yet the degree to which long-term decline is caused by chronic feelings of stereotype threat is unclear. The reverse causal order is easy to imagine.
Even the data regarding the longitudinal impact of complex thought are causally ambiguous. Consider the Nun Study of Aging and Alzheimer’s Disease. Beginning in 1986, a team led by David Snowdon examined brief autobiographies written by young women during the 1930s as part of the process of becoming nuns. The young women were, on average, twenty-two years of age. Their mental functioning was tested when they reached old age and brain integrity then assessed via autopsy. One of the advantages of the study is that after joining the convent the nuns led regimented and similar lives with few outside influences.
Snowdon found that nuns whose autobiographies exhibited a greater density of ideas were more likely to remain mentally sharp in late life.26 One interpretation of this finding is that complex thought led to complex wiring and brains that were more robust to the ravages of aging. The complex thought shown in the autobiographies might, however, simply be a sign of having a better brain to begin with. There is evidence that engaging in a lot of complex thought leads to changes in the brain,27 but the effects of complex thought on long-term mental functioning may, in fact, be negligible.
Positive Impact
Consider the common finding that older adults tend to have smaller circles of close friends. This might seem to suggest that older adults no longer have the energy or cognitive capacity to maintain large social networks. Socio-Emotional Selectivity Theory (SST) suggests that shrinking social networks are not a sign of functional loss, but an emotional response to impending death.28 This theory also explains another well-known effect of aging: older adults tend to focus on and have better memory for positive information, whereas younger adults show equal attention and memory for both positive and negative information.29
SST may yet prove to be the explanation for these effects, but recent research raises alternative possibilities. The social networks of monkeys also shrink as they age.30 Although monkeys may possess some capacity for self-recognition,31 they lack the self-awareness and reflection to understand their eventual demise.32 It seems unlikely that older monkeys are trying to enjoy their remaining days among close friends. Instead, they lack the energy they once had, and find it easier to restrict their social circle. Older monkeys and older humans may not engage in the same behavior for the same reasons but it is entirely possible that there is a common factor at work in both.
Older adults not only show declines in muscle, bone, and brain, but also a gradual deterioration of their immune systems. One potential way to enhance immune functioning is to maintain a positive outlook, a conclusion that the authors of a recent study describe as “provocative but not definitive.”33 Perhaps the aging positivity effect is a strategy for maintaining strong immune functioning. A recent study replicated the aging positivity effect, and showed that better memory for positive but not negative information was associated with higher CD4+ counts and lower CD4+ activation one and two years later.34 Higher CD4+ counts, within the normal range, indicate a greater preparedness to fight off illness. In contrast, activation of CD4+s above the normal range indicates that the person is busy fighting infection and is in poor health.
This relationship between positivity in memory and CD4+s suggests an evolutionary explanation for the aging positivity effect. Although selective pressure is non-existent on older individuals, research suggests that grandparents enhance the survival of their grandchildren. Church records from eighteenth-century Finland show that for every decade a woman lived past the age of fifty, she gained two extra living grandchildren. A form of kin selection may well be at work.
These studies require replication and extension, but they suggest that the interpretation provided by SST might be misguided. The change in time perspective that is thought to underlie shrinking social networks and increased positivity may have nothing to do with either.
Conclusions
Attitudes may indeed play an important role in the magnitude of cognitive and physical losses associated with aging. Suggestive evidence to this effect can be found in the literature. This in turn raises the possibility that such losses might be amenable to interventions that could enhance cognitive functioning and extend life. There is also evidence that age-related changes that appear to be losses might instead reflect changing priorities. Despite the large number of impressive studies showing such positive effects, the causal role of attitudes in most, if not all, age-related losses in cognitive and physical functioning remains unclear.
