RETIREMENT RESEARCH November 2016, Number 16-17 COGNITIVE AGING: A PRIMER By Anek Belbase and Geoffrey T. Sanzenbacher* Introduction Cognitive aging has received growing attention in will generally need more time to learn new skills or recent years as many researchers have documented a concepts; and 2) many retirees can continue to man- significant age-related decline in the brain’s process- age their own financial affairs in their 70s and 80s, ing ability. This decline could potentially undermine though about one quarter will likely develop a cogni- retirement security in two ways: 1) by limiting the tive impairment that will pose a threat to their finan- ability to work longer; and 2) by eroding the capacity to cial independence. manage finances in retirement. This brief summarizes the explosion of recent research on cognitive aging by answering basic ques- Defining and Measuring tions about what researchers are learning and why their findings matter to retirement experts and the Cognitive Ability public. This overview is the first brief in a series of A basic definition of cognition – “the act or process of three; the other two will focus on how cognitive aging knowing” – points out two aspects of cognitive ability: affects the ability of individuals to work between ages 1) having knowledge; and 2) acquiring knowledge.1 50-70 and to handle personal finances between ages Psychologists commonly refer to knowledge as “crys- 70-90. tallized intelligence” and the ability to process new in- The discussion proceeds as follows. The first sec- formation as “fluid intelligence.” Figure 1 (on the next tion introduces definitions and measures of cognitive page) illustrates how overall cognitive ability depends ability. The second section discusses how researchers on these two aspects of cognition and provides some identify changes in cognitive ability with age, while the examples. third summarizes their findings. The fourth section Most real-world activity relies on both crystal- discusses how age-related changes in different cogni- lized and fluid intelligence. Some researchers have tive capacities can affect real-world performance. The attempted to measure performance on everyday final section concludes that: 1) most older workers can tasks directly. For example, driving performance maintain their productivity up to age 70, although they * Anek Belbase is a research fellow at the Center for Retirement Research at Boston College (CRR). Geoffrey T. Sanzen- bacher is a research economist at the CRR. 2 Center for Retirement Research Figure 1. Components of Cognitive Ability Measuring Changes in Cognitive ability Cognitive Ability While a variety of tools exist to measure different aspects of cognitive ability at a given point in time, Crystallized intelligence Fluid intelligence measuring changes over the life-cycle requires its own methodologies. For this purpose, researchers have Problem Vocabularly Procedural Reaction solving & relied on two basic study designs: 1) cross-sectional Memory & facts knowledge speed planning studies, which compare the performance of, say, a 30-year old to a 60-year old in a test conducted at the Source: Authors’ illustration. same point in time; and 2) longitudinal studies, which compare the performance of the same individual at, say, ages 30 and 60. has been studied extensively using simulators, with Cross-sectional studies are relatively easy to admin- performance depending on both knowledge, such as ister, but tend to overestimate the rate of cognitive de- knowing traffic rules, and fluid ability, such as reacting cline because of cohort effects – factors such as better quickly to avoid hazards.2 But the results of such test- education and nutrition have led more recent cohorts ing are hard to extrapolate to other tasks, because they to perform better on tests than earlier cohorts. As a do not address why performance varies. For example, result, any point-in-time comparison will yield large reduced driving ability in one’s 70s and 80s may not differences between the test scores of the young and equate to poor financial capacity because driving could old that may not be predictive of the younger genera- have deteriorated due to a decline in reaction speed, tion’s cognitive path.6 which is unrelated to financial decision-making ability. Longitudinal studies eliminate this problem by fol- On the other hand, if driving performance declined lowing the same individuals over time. However, this due to difficulty remembering the meaning of road approach is expensive, since studies must last decades signs, the underlying memory problems could affect to be useful. They also can underestimate the rate of financial judgement as well. age-related decline in cognitive ability for two reasons: Standardized tests offer an alternative to simulated 1) people who drop out of the study may be more tasks that is more generalizable because it identifies likely to have experienced steep decline (due to poor the processes underlying behavior. The IQ test, ini- health or dementia); and 2) taking the same test on tially developed to assess whether young children had multiple occasions leads to improvements in perfor- the cognitive ability to attend first grade, serves as a mance due to practice. To make matters worse, both model for many of these tests.3 This type of cognitive the longitudinal and cross-sectional approaches suffer test typically consists of multiple choice questions that from “noise” – the same person can do differently assess a mix of crystallized and fluid intelligence. on the same test at different times, even if taken just But standardized tests are an indirect measure of seconds apart. cognitive ability. A growing body of research relies on Fortunately, researchers have developed ways to brain scans to directly observe brain activity. These correct for these shortcomings, such as taking the av- scans are usually administered while participants per- erage of several tests to reduce the effect of noise from form a task like mentally rotating three-dimensional any single test. Problems associated with cross-sec- images.4 Such scans have allowed researchers to tional and longitudinal studies can also be addressed explain where in the brain different cognitive activities through statistical techniques. For example, in cross- originate. This knowledge, in turn, has helped explain sectional studies, one can account for the differences how age-related changes in specific brain regions in test scores caused by differences in education by could affect cognitive ability and performance.5 comparing scores only among individuals with similar Issue in Brief 3 educational attainment. In longitudinal studies, one This loss in neural matter follows a pattern – from the can figure out how much, on average, practice boosts front to the back of the brain and from the outer parts test scores, and adjust the scores of people who take of the brain to the inner parts of the brain.7 Figure 3 the test often to reflect the boost they received from shows these patterns in a brain scan, with the older this practice. Figures 2a and 2b show the value of brains having lower concentrations of neurotransmit- these adjustments. ter receptors in the front of the brain, as indicated by low amounts of red and green shading. Figure 2. Age-related Changes in Episodic Memory Figure 3. Difference in Concentration of a. Unadjusted Dopamine Receptors, by Age 10 Estimated memory change (T score) 0 -10 -20 Cross-sectional data (unadjusted) 24 years 44 years 86 years Longitudinal data (unadjusted) -30 Note: These images are PET scans from three subjects, 35 40 45 50 55 60 65 70 75 80 85 showing the concentration of dopamine receptors in the Age brain. Red indicates highest concentrations, dark spots indicate lowest. b. Adjusted Source: Brookhaven National Laboratory (1998). 10 Estimated memory change (T score) These changes in the brain are correlated with pre- 0 dictable age-related changes in cognitive ability.8 On average, starting in an individual’s 30s or 40s, reaction -10 speed starts to slow, working memory starts to deterio- rate, and other components of fluid intelligence begin to weaken, with noticeable declines in fluid intelli- -20 gence widespread by the time people are in their 50s Cross-sectional data (adjusted for education) Longitudinal data (adjusted for practice) and 60s. But crystallized intelligence tends to increase -30 or remain steady into one’s 70s and 80s among people 35 40 45 50 55 60 65 70 75 80 85 without cognitive impairment. Age With declining fluid intelligence on one hand, Source: Adapted from Nyberg et al. (2012). and resilient crystallized intelligence on the other, the ability to perform everyday tasks can either decline or improve with age, depending on both the task and What We Know About the person. With respect to tasks, older adults have a harder time reading or hearing when confronted with Age-related Cognitive Change distractions, are more prone to making errors when asked to perform under time pressure, and are less Several themes have emerged from research on age- able to acquire and transfer new information.9 On related cognitive change using the methods outlined the other hand, older adults tend to score better than above. Brain scans reveal that the brain loses matter younger adults on tests of general and domain-specific as one ages, with acceleration toward the end of life. knowledge.10 4 Center for Retirement Research Of course, within any age group, the level of and 3) the capacity of the brain to acquire completely cognitive ability varies, as does the degree of cognitive new functions, such as learning how to play a musical change. Figure 4 illustrates these variations using a instrument for the first time, is severely diminished test of cognitive function that incorporates both fluid due to changes in brain structure. and crystallized intelligence. The test was adminis- Since different cognitive capacities decline at dif- tered several times over a 7-year period to a sample of ferent rates, the effect of cognitive aging on real-world 3,075 individuals who were ages 70-79 at the start of performance depends on the situation. In situations the study. In addition to showing variation in the level where an individual has direct experience and exten- of cognitive score at age 70, the figure identifies three sive practice – like paying bills or speaking to a cus- distinct groups who differ in the changes they experi- tomer service representative – age generally improves ence over time. The “maintainers” have a higher ini- performance through one’s 50s and 60s, with little tial score and show no decline over the 7-year period, decline thereafter; performance speed, however, could while the other two groups have lower initial scores decrease, especially in one’s 70s and 80s. In situa- and show minor or major declines. tions where an individual has related experience, but reactions are not automatic, like driving on unfamiliar streets, age generally leads to decreased performance starting in one’s 60s. Declines in performance are Figure 4. Cognitive Scores Over 7-Year Period for especially significant when a task is complex, such Individuals Initially Ages 70-79 as driving on unfamiliar streets on a rainy night. In 100 situations where an individual has little or no relevant experience, like learning a new language, age often results in significant declines in the quality and speed of performance starting as early as childhood. Cognitive score 90 80 Conclusion Maintainers Minor decliners Reviewing the ways in which cognitive aging could Major decliners affect real-world performance provides useful insights 70 for anyone concerned with the well-being of retirees, Y1 Y3 Y5 Y8 from policymakers to financial planners to individuals Testing year themselves. Source: Reproduced from Yaffe et al. (2009). One way that cognitive change could affect retire- ment security is by limiting the ability to work. In this respect, the wide range of cognitive skills that older workers build and maintain as they age implies How Change in Ability Affects that most workers can remain productive in their Real-World Performance 50s and 60s despite cognitive aging. This finding is supported by numerous studies that show insignifi- cant age-related losses in productivity across a variety The research clearly shows that fluid intelligence de- of occupations.11 However, declines in processing clines with age while crystallized intelligence accumu- capacity and speed can affect the performance of lates, and that the brain changes in both structure and some workers engaged in complex tasks under time activity. These changes together predict the follow- pressure. For example, the performance of air- ing three patterns: 1) the brain acquires the ability to traffic controllers, who must track the flight paths of react intelligently and automatically to a wider range multiple airplanes at once while also quickly react- of situations with age due to increased crystallized ing to unusual situations, declines significantly by intelligence; 2) the maximum capacity and speed for age 56.12 And diminished ability to adapt, or acquire processing information at any given moment dimin- completely new skills, implies that older workers will ishes with age, largely due to declining fluid abilities; require more time to adjust to occupational changes, Issue in Brief 5 a finding supported by studies that show that the abil- Endnotes ity to learn new material (both in the lab and on the job) diminishes with age.13 1 Merriam-Webster’s Collegiate Dictionary (2010). A second way in which cognitive change could affect retirement security is through a diminished 2 Andrews and Westerman (2012). capacity to manage money. This skill is largely learned through experience; thus, older individuals typically 3 Other prominent tests include the Scholastic have already acquired the cognitive skills to carry out Aptitude Test (SAT) for assessing general academic common tasks, like paying bills on time.14 However, potential and the Armed Forces Vocational Aptitude due to the increasing prevalence of 401(k) plans – Battery test for determining suitability for an occupa- where (unlike traditional pensions) retirees must tion. For examples of some other common cognitive decide how to invest their nest egg and how much tests, see the Appendix. to draw from it each month – even retirees used to making financial decisions might need help from a 4 For example, see Ivanoff, Branning, and Marois financial expert. And retirees who take over finan- (2009) or Langenecker, Nielson, and Rao (2004). cial matters from a spouse (due to death or illness) must learn new financial concepts in their 70s and 5 For example, see Casey et al. (2005). 80s if they want to avoid making financial mistakes.15 Finally, the risk of dementia and severe cognitive 6 For an excellent analysis of the methodological con- impairment rises exponentially in one’s 70s and 80s.16 siderations, see Schaie and Willis (2015), Chapter 2. This pattern means that a significant share of retirees will eventually need help managing their finances in 7 See Chapter 1 of Craik and Salthouse (2008), retirement, which includes being protected against DeCarli et al. (1995), Pantoni and Garcia (1997), or financial fraud and abuse. Sullivan et al. (1995). The next two briefs in this series will elaborate on how these two topics – work and finances – are af- 8 Individuals who show greater changes in brain fected by cognitive decline. structure and activation also show greater decline in fluid cognitive abilities; brain regions that show the most deterioration correspond to a decline in the abilities mediated by those regions (for a summary, see Salat (2011)). 9 Mund, Bell, and Buchner (2010). 10 Ackerman (2000). 11 See Jeske and Rossnagel (2015) and Ng and Feld- man (2013). 12 Heil (1999). The Federal Aviation Authority actu- ally requires its air traffic controllers to retire at 56, with a provision allowing those with exceptional skills and experience to continue until 61. 13 Salthouse (2012). 14 Schaie and Willis (2016). 15 For example, see Agarwal et al. (2009). 16 Wilson et al. (2003). 6 Center for Retirement Research References Ackerman, Phillip L. 2000. “Domain-Specific Knowledge Ivanoff, Jason, Philip Branning, and René Marois. as the ‘Dark Matter’ of Adult Intelligence: Gf/Gc, 2009. “Mapping the Pathways of Information Personality and Interest Correlates.” The Journals of Processing from Sensation to Action in Four Dis- Gerontology Series B: Psychological Sciences and Social tinct Sensorimotor Tasks.” Human Brain Mapping Sciences 55(2): 69-84. 30(12): 4167-4186. Agarwal, Sumit, John C. Driscoll, Xavier Gabaix, and Jeske, Debora and Christian Stamov Rossnagel. 2015. David Laibson. 2009. “The Age of Reason: Finan- “Learning Capability and Performance in Later cial Decisions Over the Life-Cycle with Implica- Working Life: Towards a Contextual View.” Educa- tions for Regulation.” Brookings Papers on Econom- tion and Training 57(4): 378-391. ic Activity 2009(2) 51-117. Langenecker, Scott A., Kristy A. Nielson, and Stephen M. Andrews, Elizabeth C. and Stephen J. Westerman. Rao. 2004. “fMRI of Healthy Older Adults uring D 2012. “Age Differences in Simulated Driving Stroop Interference.” Neuroimage 21(1): 192-200. Performance: Compensatory Processes.” Accident Analysis & Prevention 45: 660-668. Merriam-Webster’s Collegiate Dictionary. 2010. Spring- field, MA: Merriam-Webster, Inc. Brookhaven National Laboratory. 1998. “New Study Connects Brain Chemistry to Old Age’s Most Mund, Iris, Raoul Bell, and Axel Buchner. 2010. “Age Common Symptoms: Decreases in Motor Skills Differences in Reading with Distraction: Sensory and Mental Agility Could be Preventable.” Upton, or Inhibitory Deficits?” Psychology and Aging 25(4): NY. Available at: https://www.bnl.gov/bnlweb/ 886-897. pubaf/pr/1998/bnlpr030298a.html. Ng, Thomas W. H., and Daniel C. Feldman. 2013. Casey, B. J., Nim Tottenham, Conor Liston, and Sarah “How Do Within-Person Changes Due to Aging Durston. 2005. “Imaging the Developing Brain: What Affect Job Performance?” Journal of Vocational Have We Learned About Cognitive Development?” Behavior 83(3) 500-513. Trends in Cognitive Sciences 9(3): 104-110. Nyberg, Lars, Martin Lövdén, Katrine Riklund, Ulman Craik, Fergus and Timothy Salthouse. 2008. The Lindenberger, and Lars Bäckman. 2012. “Memory Handbook of Aging and Cognition: Third Edition. Aging and Brain Maintenance.” Trends in Cognitive New York, NY: Psychology Press. Sciences 16(5): 292-305. DeCarli, Charles, D. M. Murphy, M. Tranh, C. L. Pantoni, Leonardo and Julio H. Garcia. 1997. “Cogni- Grady, J. V. Haxby, J. A. Gillette, J. A. Salerno et al. tive Impairment and Cellular/Vascular Changes in 1995. “The Effect of White Matter Hyperintensity the Cerebral White Matter.” Annals of the New York Volume on Brain Structure, Cognitive Perfor- Academy of Sciences 826(1): 92-102. mance, and Cerebral Metabolism of Glucose in 51 Healthy Adults.” Neurology 45(11): 2077-2084. Salat, David H. 2011. “The Declining Infrastructure of the Aging Brain.” Brain Connectivity 1(4): 279-293. Heil, Michael C. 1999. “Air Traffic Control Specialist Age and Cognitive Test Performance.” Report to Salthouse, Timothy A. 2012. “Consequences of Age- the U.S. Department of Transportation Federal Avia- Related Cognitive Declines.” Annual Review of tion Administration. Psychology 63: 201-226. Issue in Brief 7 Schaie, K. Warner and Sherry Willis. 2016. Handbook of the Psychology of Aging: 8th Edition. Boston, MA: Academic Press. Sullivan, Edith V., Laura Marsh, Daniel H. Mathalon, Kelvin O. Lim, and Adolf Pfefferbaum. 1995. “Age- Related Decline in MRI Volumes of Temporal Lobe Gray Matter but not Hippocampus.” Neurobi- ology of Aging 16(4): 591-606. Wilson, R. S., L. A. Beckett, J. L. Bienias, D. A. Evans, and D. A. Bennett. 2003. “Terminal Decline in Cognitive Function.” Neurology 60(11): 1782-1787. Yaffe, K., Fiocco, A. J., Lindquist, K., Vittinghoff, E., Simonsick, E. M., Newman, A. B., and Harris, T. B. 2009. “Predictors of Maintaining Cognitive Function in Older Adults: The Health ABC Study.” Neurology 72(23): 2029-2035. APPENDIX Issue in Brief 9 Table A1. Tests of Cognitive Ability Test name Format Time to complete Description The test requires the examinee to transcribe, from Non-verbal Timed, <90 Digit Symbol Substitution Test memory, a set of symbols corresponding to the memory seconds numbers 1 to 9. Not timed, 5-10 A 30-point questionnaire used to measure Mini-Mental State Examination Battery minutes cognitive impairment. A 60-point multiple choice test in which the Non-verbal, Timed, 35-40 Raven’s Progressive Matrices subject is asked to identify the missing element Aptitude minutes that completes a pattern. Participants are given words that are presented in Stroop Interference Task Reaction Timed/reaction certain colors and are asked to say the color of a word. Test of visual attention and task switching in Trail Making Test Non-verbal Timed which the subject connects a set of 25 dots as quickly as possible while maintaining accuracy. An IQ test designed to measure intelligence and Weschler Adult Intelligence Scale Aptitude Timed, 40 minutes cognitive ability in adults and adolescents. The task is to match cards according to different Not timed, 20-30 Wisconsin Card Sorting Test Non-verbal principles – by color, form, or number of shapes, minutes without being given these principles. Source: Authors’ compilation from various sources. RETIREMENT RESEARCH About the Center Affiliated Institutions The mission of the Center for Retirement Research The Brookings Institution at Boston College is to produce first-class research Syracuse University and educational tools and forge a strong link between Urban Institute the academic community and decision-makers in the public and private sectors around an issue of criti- cal importance to the nation’s future. To achieve Contact Information Center for Retirement Research this mission, the Center sponsors a wide variety of Boston College research projects, transmits new findings to a broad Hovey House audience, trains new scholars, and broadens access to 140 Commonwealth Avenue valuable data sources. Since its inception in 1998, the Chestnut Hill, MA 02467-3808 Center has established a reputation as an authorita- Phone: (617) 552-1762 tive source of information on all major aspects of the Fax: (617) 552-0191 retirement income debate. 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