Although differences among people are frequently assumed to increase with age, cross-sectional comparisons of measures of brain structure and measures of cognitive functioning often reveal similar magnitudes of between-person variability across most of adulthood. The phenomenon of nearly constant variability despite systematically lower means with increased age suggests that individual differences in rates of aging may be relatively small, particularly compared to the individual differences apparent at any age. The current study examined between-person variability in cross-sectional means and in short-term longitudinal changes in five cognitive abilities at different ages in adulthood. The variability in both level and change in cognitive performance was found to be similar among healthy adults from 25 to 75 years of age in all five cognitive abilities. Furthermore, the correlations between scores at the first and second occasions were very high, and nearly the same magnitude at all ages. The results indicate that between-person differences in short-term cognitive changes are not inevitably greater among healthy older adults than among young adults.
A total of 3,781 healthy adults between 18 and 97 years of age completed trait anxiety and depressive symptoms inventories and also performed a battery of cognitive tests. Consistent with recent research on cognitive abilities, the cognitive variables could be organized into a hierarchical structure, with 5 first-order abilities and a single g-factor representing the variance common to the first-order abilities at the top of the hierarchy. Analyses were conducted to determine where in this hierarchy effects associated with trait anxiety and depressive symptoms were operating. The results indicated that trait anxiety and depressive symptoms had significant relations at the highest level in the hierarchy of cognitive abilities, but few relations of either characteristic were evident on the cognitive abilities, or on measures of working memory, after controlling influences at the g-factor level.
cognitive abilities; mood effects; level of influence; hierarchical structure of cognitive ability
Longitudinal change in five cognitive abilities was investigated to determine if the direction or magnitude of change was related to the individual’s ability level. Adults between 18 and 97 years of age performed three versions of 16 cognitive tests on two occasions separated by an average of 2.7 years. In order to control for influences associated with regression toward the mean, level of ability was determined from scores on the first version of the cognitive tests on the first occasion, and across-occasion change was examined on the second and third versions. Change in every cognitive ability was significantly more negative with increased age. However, there was little indication of ability-dependent change in any of the five cognitive abilities, either in differences between composite scores, or in estimates of latent change. Although there are reasons to expect cognitive change to be less negative at either high or low levels of ability, these data suggest that neither the direction nor magnitude of change is related to initial ability when influences of regression toward the mean are controlled.
aging; longitudinal change; ability-dependent change; regression toward the mean
Two major challenges facing researchers interested in cognitive change are that measures of change are often not very reliable, and they may reflect effects of prior test experience in addition to the factors of primary interest. One approach to dealing with these problems is to obtain multiple measures of change on parallel versions of the same tests in a measurement burst design. A total of 783 adults performed three parallel versions of cognitive tests on two occasions separated by an average of 2.6 years. Performance increased substantially across the three sessions within each occasion, and for all but vocabulary ability these within-occasion improvements were considerably larger than the between-occasion changes. Reliabilities of the changes in composite scores were low, but averages of the three changes had larger, albeit still quite modest, reliabilities. In some cognitive abilities individual differences were evident in the relation of prior test experience and the magnitude of longitudinal change. Although multiple assessments are more time consuming than traditional measurement procedures, the resulting estimates of change are more robust than those from conventional methods, and also allow the influence of practice on change to be systematically investigated.
Longitudinal; Aging; Neurocognitive; Reliable change; Measurement burst; Gains and losses
Adult age differences in a variety of cognitive abilities are well documented, and many of those abilities have been found to be related to success in the workplace and in everyday life. However, increased age is seldom associated with lower levels of real-world functioning, and the reasons for this lab-life discrepancy are not well understood. This article briefly reviews research concerned with relations of age to cognition, relations of cognition to successful functioning outside the laboratory, and relations of age to measures of work performance and achievement. The final section discusses several possible explanations for why there are often little or no consequences of age-related cognitive declines in everyday functioning.
cognitive aging; cognitive functioning; job performance; accommodations; typical versus maximal performance
Individual differences associated with age and various neurological conditions are often found in many different neuropsychological and cognitive variables. These variables are frequently treated as though they were independent of one another, with the results interpreted in terms of effects on task-specific processes. However, an alternative perspective evaluates the breadth of the individual difference influences, and takes relations with other variables into account when considering effects on specific neurocognitive variables. This analytical procedure is illustrated in analyses of the WAIS-IV and WMS-IV standardization data, and of data from the Virginia Cognitive Aging Project.
Cognition; Memory; Aging; Correlation study; Statistical models; Multivariate analysis
Significant declines in longitudinal comparisons of neurocognitive performance are seldom evident until adults are in their 60s or older, but relatively little is known about the existence, or nature, of age-related changes at earlier periods in adulthood. The current research was designed to address this issue by examining characteristics of change in measures from 12 neuropsychological and cognitive tests at different periods in adulthood. Although change was largely positive for adults under about 55 years of age and frequently negative for adults at older ages, the reliabilities of the changes in the neuropsychological and cognitive variables were similar at all ages. Furthermore, there were few systematic relations of age on the reliability-adjusted correlations between the changes in composite scores representing different abilities. These results imply that although neurocognitive declines may not be apparent at young ages because of positive retest effects or other factors, at least in some respects longitudinal changes may have nearly the same meaning across all of adulthood.
aging; cognitive change; longitudinal; reliability
Interpretation of cognitive change has been complicated because different influences on change are not easily distinguished. In this study, longitudinal cognitive change was decomposed into a component related to the length of the interval between test occasions (i.e., time-dependent change) and a component unrelated to the test-retest interval (i.e., time-independent change). Influences of age on the two hypothesized components were investigated in a sample of more than 1,500 adults for whom the intervals between test occasions ranged from less than 1 year to more than 8 years. Although overall change was negatively related to age for all seven composite cognitive variables, little or no effect of age was apparent for the time-dependent component of change. The results suggest that the relations between age and cognitive change over intervals of less than 8 years are largely influenced by factors operating at or near the initial test occasion.
longitudinal; cognitive change; aging; retest interval
Although an increasing number of studies have investigated relations between dimensions of personality and level of cognitive functioning, the research results have been somewhat inconsistent. Furthermore, relatively little is known about whether the personality–cognition relations vary as a function of age in adulthood. The current project examined these issues with data from a sample of 2,317 adults between 18 and 96 years of age who each completed a personality inventory and performed a broad battery of cognitive tests. The results revealed strong relations of the personality trait of Openness with several distinct cognitive abilities and smaller relations of other personality traits with specific cognitive abilities. Comparisons across different age groups indicated that the personality–cognition relations were both qualitatively and quantitatively similar across the adult years.
Big Five; cognition; age; structural invariance
The Wechsler Adult Intelligence Scale–fourth edition (WAIS-IV) and the Wechsler Memory Scale–fourth edition (WMS-IV) were co-developed to be used individually or as a combined battery of tests. The independent factor structure of each of the tests has been identified; however, the combined factor structure has yet to be determined. Confirmatory factor analysis was applied to the WAIS-IV/WMS-IV Adult battery (i.e., age 16-69 years) co-norming sample (n = 900) to test 13 measurement models. The results indicated that two models fit the data equally well. One model is a seven-factor solution without a hierarchical general ability factor: Verbal Comprehension, Perceptual Reasoning, Processing Speed, Auditory Working Memory, Visual Working Memory, Auditory Memory, and Visual Memory. The second model is a five-factor model composed of Verbal Comprehension, Perceptual Reasoning, Processing Speed, Working Memory, and Memory with a hierarchical general ability factor. Interpretative implications for each model are discussed.
WAIS-IV; WMS-IV; joint factor analysis; confirmatory factor analysis; memory; working memory; intelligence
There are many reports of relations between age and cognitive variables and of relations between age and variables representing different aspects of brain structure, and a few reports of relations between brain structure variables and cognitive variables. These findings have sometimes led to inferences that the age-related brain changes cause the age-related cognitive changes. Although this conclusion may well be true, it is widely recognized that simple correlations are not sufficient to warrant causal conclusions, and other types of correlational information, such as mediation and correlations between longitudinal brain changes and longitudinal cognitive changes, also have limitations with respect to causal inferences. These issues are discussed, and the existing results on relations of regional volume, white matter hyperintensities, and DTI measures of white matter integrity to age and to measures of cognitive functioning are reviewed. It is concluded that at the current time the evidence that these aspects of brain structure are neuroanatomical substrates of age-related cognitive decline is weak. The final section contains several suggestions concerned with measurement and methodology that may lead to stronger conclusions in the future.
The commentaries on my article contain a number of points with which I disagree, but also several with which I agree. For example, I continue to believe that the existence of many cases in which between-person variability does not increase with age indicates that greater variance with increased age is not inevitable among healthy individuals up to about 80 years of age. I also do not believe that problems of causal inferences from correlational information are more severe in the cognitive neuroscience of aging than in other research areas; instead, I contend that neglect of these problems has led to confusion about neurobiological underpinnings of cognitive aging. I agree that researchers need to be cautious in extrapolating from cross-sectional to longitudinal relations, but I also note that even longitudinal data are limited with respect to their ability to support causal inferences.
Increased age has been found to be associated with differences in affect and personality which have been interpreted in terms of better emotional regulation and increased maturity. However, these findings have largely been based on self-report data, and the primary goal of the current research was to investigate the hypothesis that age-related differences in affect and in certain desirable personality traits might, at least partially, reflect age differences in social desirability. As expected, increased age was associated with lower levels of negative affect and neuroticism and higher levels of positive affect, life satisfaction, agreeableness and conscientiousness, and scores on the social desirability scale were positively related to age and to desirable self-report characteristics, but negatively related to undesirable self-report characteristics. Importantly, controlling for the variance in the social desirability measure resulted in less positive age trends in both types of self-report measures.
self-reports; affect; personality; social desirability; aging
A total of 1,576 adults between 18 and 95 years of age performed a battery of cognitive tests and the Connections version of the trail making test twice, with an average interval between assessments of 2.5 years. Consistent with previous results, speed ability and fluid cognitive ability were strongly correlated with trail making performance. Neither speed nor fluid cognitive ability at the first occasion predicted longitudinal changes in trail making performance, but there were significant correlations between the changes in these abilities and the changes in trail making performance. These results indicate that individual differences in speed and fluid cognitive abilities are associated with individual differences in trail making performance both at a single point in time (cross-sectional differences), and in the changes over time (longitudinal changes).
longitudinal change; cognitive abilities; age differences and changes
The cognitive abilities involved in the Connections (Salthouse, et al., 2000) version of the trail making test were investigated by administering the test, along with a battery of cognitive tests and tests of complex span and updating conceptualizations of working memory, to a sample of over 3,600 adults. The results indicate that this variant of the trail making test largely reflects individual differences in speed and fluid cognitive abilities, with the relative contributions of the two abilities varying according to particular measure of performance considered (e.g., difference, ratio, residual). Relations of age on trail making performance were also examined. Although strong age differences were evident in the Connections and working memory measures, with both sets of variables there was nearly complete overlap of the age differences with individual differences in speed and fluid cognitive abilities.
neuropsychological assessment; meaning of tests; working memory; fluid ability; age differences
The current project investigated why people with high levels of Openness/Intellect tend to have higher levels of cognitive functioning than people with lower levels of Openness/Intellect. We hypothesized that the positive relationship between Openness/Intellect and cognition might be attributable to more open people being more likely to engage in cognitively stimulating activities that are beneficial for cognitive functioning. Three conceptualizations of activity engagement based on: (a) self ratings of duration and intensity of engagement; (b) perceived routineness of one’s activities; and (c) disposition to engage in cognitively stimulating activities, were investigated as possible mediators of the Openness/Intellect-cognition relations. Although several of the relevant simple correlations were of moderate size and statistically significant, we found little evidence that activity engagement mediated the relations between Openness/Intellect and cognition.
Openness/Intellect; cognition; engagement; activities; need for cognition; busyness; routine
Many analytical methods are not very sensitive to change because of the difficulty of distinguishing short-term fluctuation from the developmental change of primary interest. The current project investigated one possible solution to this problem in the form of a measurement-burst design in which research participants perform several versions of each test at each measurement occasion.
Over 1,200 adults across a wide-age range performed different versions of cognitive tests on several sessions at each measurement occasion.
Four methods of incorporating short-term variability were compared with respect to the magnitude of the correlations of the ability measures with each other and with respect to the magnitude of their relations with age.
The results revealed that more sensitive assessments of change can be obtained by taking short-term fluctuation into account with measurement-burst designs. In particular, capitalizing on the availability of multiple measures at each occasion to form latent constructs representing the level and change in cognitive performance may provide the most sensitive assessment of cognitive change.
Cognitive change; Intra-individual variability; Measurement burst
Approximately 2,500 adults (ages 18–97) completed multiple study-test trials of a list of unrelated words. Consistent with past research, females outperformed males in the recall task. To assess whether sex differences in recall performance were attributable to differences in acquiring and/or retaining information, the data were analyzed at the individual item level to distinguish gains (i.e., items not recalled on Trial n that were recalled on Trial n+1) and losses (i.e., items recalled on Trial n that were not recalled on Trial n+1). Being a male, increased age, lower verbal episodic memory ability, and lower vocabulary ability were associated with smaller gains and greater losses. Even when controlling for the influence of other individual difference variables, being a male was still associated with fewer gains across the majority of trials. These results suggest that one factor contributing to sex differences in recall performance are differences in acquiring new items rather than differences in retaining information across trials.
Sex Differences; Verbal Learning; Memory
Longitudinal comparisons of neurocognitive functioning often reveal stability or age-related increases in performance among adults under about 60 years of age. Because nearly monotonic declines with increasing age are typically evident in cross-sectional comparisons, there is a discrepancy in the inferred age trends based on the two types of comparisons. The current research investigated the role of practice effects in longitudinal comparisons on the discrepancy.
Longitudinal data over an average interval of 2.5 years were available on five abilities (i.e., reasoning, spatial visualization, episodic memory, perceptual speed, vocabulary) in a sample of 1,616 adults ranging from 18 to over 80 years of age. Practice effects were estimated from comparisons of the performance of people of the same age tested for either the first or second time, after adjusting for the possibility of selective attrition.
Increased age was associated with significantly more negative longitudinal changes with each ability. All of the estimated practice effects were positive, but they varied in magnitude across neurocognitive abilities and as a function of age. After adjusting for practice effects the longitudinal changes were less positive at younger ages and slightly less negative at older ages.
It was concluded that some, but not all, of the discrepancy between cross-sectional and longitudinal age trends in neurocognitive functioning is attributable to practice effects positively biasing the longitudinal trends. These results suggest that the neurobiological substrates of neurocognitive functioning may change across different periods in adulthood.
retest effects; cross-sectional versus longitudinal; within-individual neurocognitive change
Properties of cognitive change scores were compared in adults over age 70, for whom longitudinal changes are often negative, and in adults in two age groups under age 70, for whom the changes are often close to zero. Longitudinal assessments of three measures of memory and three measures of speed across an average interval of 2.4 years were obtained from a sample of 1,282 healthy adults between 18 and 92 years of age. Although substantial longitudinal declines were primarily apparent in adults 70 years of age and older, adults under and over age 70 were similar with respect to the variability and reliability of the cognitive changes, and in the magnitude of the correlations of the changes with each other and with variables which have been identified as risk factors for late-life cognitive decline and dementia. It is suggested that longitudinal changes in cognition can be considered to represent a paradox in that the mean values of the changes are more negative at older ages, but the change scores have similar measurement properties, and appear to be just as systematic, among adults under and over 70 years of age.
This review summarizes the scientific talks presented at the conference “Therapeutics for Cognitive Aging,” hosted by the New York Academy of Sciences and the Alzheimer’s Drug Discovery Foundation on May 15, 2009. Attended by scientists from industry and academia, as well as by a number of lay people—approximately 200 in all—the conference specifically tackled the many aspects of developing therapeutic interventions for cognitive impairment. Discussion also focused on how to define cognitive aging and whether it should be considered a treatable, tractable disease.
Researchers frequently attempt to identify the specific neurocognitive processes that might be responsible for differences in performance associated with neurological status or other individual difference characteristics by administering two or more conditions of an experimental task to different groups of participants, and focusing on the group-by-condition interaction as the primary outcome of interest. Three limitations of this approach are discussed, and an alternative analytical method is proposed to overcome the limitations. The method is demonstrated in analyses of data from 10 cognitive tasks in two independent studies, including two flanker tasks which are often used to assess aspects of inhibition.
Flanker inhibition; executive functions; selective influences; aging; unique individual differences
Although factor analysis is the most commonly-used method for examining the structure of cognitive variable interrelations, multidimensional scaling (MDS) can provide visual representations highlighting the continuous nature of interrelations among variables. Using data (N = 8,813; ages 17–97 years) aggregated across 38 separate studies, MDS was applied to 16 cognitive variables representative of five well-established cognitive abilities. Parallel to confirmatory factor analytic solutions, and consistent with past MDS applications, the results for young (18–39 years), middle (40–65 years), and old (66–97 years) adult age groups consistently revealed a two-dimensional radex disk, with variables from fluid reasoning tests located at the center. Using a new method, target measures hypothesized to reflect three aspects of cognitive control (updating, storage-plus-processing, and executive functioning) were projected onto the radex disk. Parallel to factor analytic results, these variables were also found to be centrally located in the cognitive ability space. The advantages and limitations of the radex representation are discussed.
cognitive control; working memory; cognitive abilities; multidimensional scaling; radex
Cross-sectional comparisons have consistently revealed that increased age is associated with lower levels of cognitive performance, even in the range from 18 to 60 years of age. However, the validity of cross-sectional comparisons of cognitive functioning in young and middle-aged adults has been questioned because of the discrepant age trends found in longitudinal and cross-sectional analyses. The results of the current project suggest that a major factor contributing to the discrepancy is the masking of age-related declines in longitudinal comparisons by large positive effects associated with prior test experience. Results from three methods of estimating retest effects in this project, together with results from studies comparing non-human animals raised in constant environments and from studies examining neurobiological variables not susceptible to retest effects, converge on a conclusion that some aspects of age-related cognitive decline begin in healthy educated adults when they are in their 20s and 30s.
cognitive aging; early adulthood; normal aging