Contextual analysis of fluid intelligence

Aging Cognition Unconfounded by Prior Test Experience

OBJECTIVE

Investigate time-related age differences in cognitive functioning without influences of prior test experience.

METHODS

Cognitive scores were compared in different individuals from the same birth years who were tested in different years, when they were at different ages. These types of quasi-longitudinal comparisons were carried out on data from three large projects: the Seattle Longitudinal Study [Schaie, K. W. (2013). Developmental influences on adult intelligence: The Seattle Longitudinal Study (2nd ed.). New York, NY: Oxford University Press], the Betula Project [Ronnlund, M., & Nilsson, L-G. (2008). The magnitude, generality, and determinants of Flynn effects on forms of declarative memory and visuospatial ability: Time-sequential analyses of data from a Swedish cohort study. Intelligence, 36, 192-209], and the Virginia Cognitive Aging Project (this study).

RESULTS

In each data set, the results revealed that the estimates of cognitive change with no prior test experience closely resembled the estimates of age relations based on cross-sectional comparisons. Furthermore, longitudinal comparisons revealed positive changes at young ages that gradually became more negative with increased age, whereas all of the estimates of change without prior test experience were negative except those for measures of vocabulary.

DISCUSSION

The current results suggest that retest effects can distort the mean age trends in longitudinal comparisons that are not adjusted for experience. Furthermore, the findings can be considered robust because the patterns were similar across three data sets involving different samples of participants and cognitive tests, and across different methods of controlling experience effects in the new data set.

Heterogeneous ability profiles may be a unique indicator of impending cognitive decline

OBJECTIVE

Prior research has found that within-person standard deviations across different neuropsychological domains are larger in various clinical groups than in healthy control groups, but little is known about the specificity of these measures to clinical conditions.

METHOD

Within-person standard deviations were computed across composite scores representing episodic memory, perceptual speed, inductive reasoning, and spatial visualization and compared in older adults differing in the amount of subsequent cognitive change, and as a function of age in a large sample of adults ranging from 18 to 89 years of age.

RESULTS

The standard deviations at an initial occasion were significantly greater in older adults who experienced the most negative longitudinal change, but relations of the standard deviations with age were only evident in adults under 65 years of age, and they were negative rather than positive.

CONCLUSIONS

These findings suggest that high values of within-person variability may have specificity in predicting late life cognitive decline.

Quantity and structure of word knowledge across adulthood

Cross-sectional and longitudinal data from moderately large samples of healthy adults confirmed prior findings of age-related declines in measures of the quantity of word knowledge beginning around age 65. Additional analyses were carried out to investigate the interrelations of different types of vocabulary knowledge at various periods in adulthood. Although the organizational structures were similar in adults of different ages, scores on tests with different formats had weaker relations to a higher-order vocabulary construct beginning when adults were in their 60's. The within-person dispersion among different vocabulary test scores was also greater after about 65 years of age. The discovery of quantitative decreases in amount of knowledge occurring at about the same age as qualitative shifts in the structure of knowledge raises the possibility that the two types of changes may be causally linked.

Correlates of cognitive change

Although there has been considerable interest in identifying potential correlates of cognitive change, results of past studies have been inconsistent. The present study incorporated a number of methodological features intended to maximize sensitivity to detect characteristics of individuals with different amounts of cognitive change. Cognitive change in 5 cognitive abilities was analyzed with 2nd-order latent growth curve models applied to data from a moderately large sample of healthy adults ranging from 18 to 99 years of age (Ns of 4,802 with 1 occasion, 2,265 with 2 occasions, and 1,128 with 3 occasions). There was significant individual difference variance in the longitudinal changes in several cognitive abilities, even in separate analyses of individuals between 18 years of age and 39, between 40 and 64, and 65 and over. Potential correlates of change included measures of self-rated health, vision, mood, personality, and lifestyle. Most of the potential correlates of change had high reliability, and several analyses were based on even more reliable factors determined by the variance common to multiple measures. Despite favorable conditions for detecting correlates of change, there was little evidence that cognitive change was moderated by any of the variables examined. Possible reasons for the inconsistent results regarding correlates of cognitive change are discussed.

Frequent assessments may obscure cognitive decline

Effects of an initial testing experience on the level of cognitive performance at a 2nd occasion are well documented. However, less is known about the effects of additional testing experiences beyond the 1st on the amount of cognitive change over a specified interval. This issue was investigated in a moderately large sample of adults between 18 and 95 years of age who performed a battery of cognitive tests either 2 or 3 times at variable intervals between each assessment. Multiple regression analyses were used to examine effects of the number of assessments on change while controlling the length of the interval between the 1st and last assessments. Change in each of 5 cognitive domains was less negative when there was an intervening assessment. To illustrate, for adults between 65 and 95 years of age, the estimated change from a 1st to a 2nd assessment across an average interval of 3.9 years was -.25 standard deviation units (p < .01), but it was only -.06 standard deviation units, and not significantly different from 0, when an intervening assessment occurred during the interval. These results indicate that cognitive change may not be detected when individuals are assessed frequently with relatively short intervals between the assessments.

Achievement-Relevant Personality: Relations with the Big Five and Validation of an Efficient Instrument

Many achievement-relevant personality measures (APMs) have been developed, but the interrelations among APMs or associations with the broader personality landscape are not well-known. In Study 1, 214 participants were measured on 36 APMs and a measure of the Big Five. Factor analytic results supported the convergent and discriminant validity of five latent dimensions: performance, mastery, self-doubt, effort, and intellectual investment. Conscientiousness, neuroticism, and openness to experience had the most consistent associations with APMs. We constructed a more efficient scale- the Multidimensional Achievement-Relevant Personality Scale (MAPS). In Study 2, we replicated the factor structure and external correlates of the MAPS in a sample of 359 individuals. Finally, we validated the MAPS with four indicators of academic performance and demonstrated incremental validity.

The role of education and verbal abilities in altering the effect of age-related gray matter differences on cognition

Evidence suggests that individual variability in lifetime exposures influences how cognitive performance changes with advancing age. Brain maintenance and cognitive reserve are theories meant to account for preserved performance despite advancing age. These theories differ in their causal mechanisms. Brain maintenance predicts more advantageous lifetime exposures will reduce age-related neural differences. Cognitive reserve predicts that lifetime exposures will not directly reduce these differences but minimize their impact on cognitive performance. The present work used moderated-mediation modeling to investigate the contributions of these mechanisms at explaining variability in cognitive performance among a group of 39 healthy younger (mean age (standard deviation) 25.9 (2.92) and 45 healthy older adults (65.2 (2.79)). Cognitive scores were computed using composite measures from three separate domains (speed of processing, fluid reasoning, and memory), while their lifetime exposures were estimated using education and verbal IQ measures. T1-weighted MR images were used to measure cortical thickness and subcortical volumes. Results suggest a stronger role for cognitive reserve mechanisms in explaining age-related cognitive variability: even with age-related reduced gray matter, individuals with greater lifetime exposures could perform better given their quantity of brain measures.

Relations between Running Memory and Fluid Intelligence

A total of 1,734 adults performed two running memory tasks and a battery of cognitive tests representing four cognitive abilities. Simultaneous analyses were used to identify unique relations of each cognitive ability, including fluid intelligence, on the running memory measures. The large sample size allowed powerful analyses of the relations at the level of individual trials, separate list lengths, and different serial positions. The results indicated that the relations of running memory performance with cognitive abilities were remarkably constant from the first to the last trial, across different list lengths, and on successive input positions. It is proposed that an important aspect of fluid intelligence is the ability to cope with novelty and complexity, and that running memory tasks may merely be one of many ways in which those processes can be operationalized.

Do age-related increases in tip-of-the-tongue experiences signify episodic memory impairments?

Tip-of-the-tongue experiences (TOTs), in which a name is known but cannot be immediately retrieved from memory, can be a cause of concern if these experiences are viewed as a sign of memory decline. The current study was conducted to investigate the relation between age and TOT frequency, and the influence of episodic memory, which is the type of memory most often assessed to detect memory problems, on that relation. In a sample of adults, increased age was found to be associated with more TOTs across different types of materials, and additional analyses suggested that these relations between age and TOT frequency were not attributable to the use of different response criteria or to different amounts of knowledge. Because statistical control of a measure of episodic memory had little effect on the relation between age and TOT frequency, age-related increases in TOTs and age-related decreases in episodic memory appear to be at least partially independent phenomena.

Effects of age and ability on components of cognitive change

Prior experience with a cognitive task is often associated with higher performance on a second assessment, and these experience effects can complicate the interpretation of cognitive change. The current study was designed to investigate experience effects by obtaining measures of cognitive performance separated by days and by years. The analyses were based on data from 2017 adults with two longitudinal occasions, of whom 948 had also completed a third occasion, with each occasion consisting of three parallel versions of the tests on separate sessions. Change across short intervals was typically positive, and greater among older adults and adults with low levels of cognitive ability, whereas change over intervals of approximately three years was often negative, particularly at older ages. In contrast to the expectation that change over short intervals might be informative about change over longer intervals, relations between short-term change and long-term change were negative, as the individuals who gained the most with assessments separated by days tended to experience the greatest losses across assessments separated by years.

Complementary cognitive capabilities, economic decision making, and aging

Fluid intelligence decreases with age, yet evidence about age declines in decision-making quality is mixed: Depending on the study, older adults make worse, equally good, or even better decisions than younger adults. We propose a potential explanation for this puzzle, namely that age differences in decision performance result from the interplay between two sets of cognitive capabilities that impact decision making, one in which older adults fare worse (i.e., fluid intelligence) and one in which they fare better (i.e., crystallized intelligence). Specifically, we hypothesized that older adults' higher levels of crystallized intelligence can provide an alternate pathway to good decisions when the fluid intelligence pathway declines. The performance of older adults relative to younger adults therefore depends on the relative importance of each type of intelligence for the decision at hand. We tested this complementary capabilities hypothesis in a broad sample of younger and older adults, collecting a battery of standard cognitive measures and measures of economically important decision-making "traits"--including temporal discounting, loss aversion, financial literacy, and debt literacy. We found that older participants performed as well as or better than younger participants on these four decision-making measures. Structural equation modeling verified our hypothesis: Older participants' greater crystallized intelligence offset their lower levels of fluid intelligence for temporal discounting, financial literacy, and debt literacy, but not for loss aversion. These results have important implications for public policy and for the design of effective decision environments for older adults.

General fluid-type intelligence is related to indices of white matter structure in middle-aged and old adults

General fluid-type intelligence (gF) reflects abstract reasoning and problem solving abilities, and is an important predictor for lifetime trajectories of cognition, and physical and mental health. Structural and functional neuroimaging studies have demonstrated the role of parieto-frontal gray matter, but the white matter (WM) underpinnings of gF and the contribution of individual gF components to gF-WM relationship still need to be explored. The aim of this study was to characterize, in a sample of 100 healthy middle-aged and old subjects (mean=63.8 years), the relationship between gF and indices of WM structure obtained from diffusion tensor magnetic resonance imaging (DT-MRI) (fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD)). gF was estimated by principal component analysis including measures of episodic memory, reasoning, and processing speed. Tract-based spatial statistics and permutation-based inference statistics were used to test the association between gF and WM indices, while controlling for the effect of age and sex. We hypothesized a positive relationship between gF and WM structure. Based on previous studies, we further hypothesized that this relationship was heavily influenced by the processing speed component of gF. We found a robust relationship between gF and DT-MRI measures of FA, RD and MD in all major WM tracts. Higher gF score was related to higher degree of WM integrity, in middle-aged as well as old individuals. Thus, the distributed relationship between gF and indices of WM microstructure is consistent with the notion that gF reflects efficient signaling between cortical areas. Furthermore, analysis of relationships between WM measures and gF components revealed an association with information processing speed and reasoning ability, but not with episodic memory. Thus, although all subcomponents loaded high on gF factor, the speed-related components were most strongly associated with DT-MRI-derived measures. These results suggest that DT-MRI can be used to parse gF.

Selectivity of attrition in longitudinal studies of cognitive functioning

OBJECTIVES

Identify characteristics distinguishing people who do and do not continue to participate in a longitudinal study and determine whether the longitudinal changes for people who continue are representative of the changes that would have occurred had longitudinal data been available from all of the initial participants.

METHOD

Moderately large samples of returning (N = 2,082) and nonreturning (N = 1,698) participants across a wide age range (i.e., 18-97 years of age) performed a battery of cognitive tests and completed personality and mood questionnaires. Differences between the groups were examined with multiple regression analyses with age, returner status, and their interaction as predictors.

RESULTS

Compared with participants who did not return, returning participants at the initial occasion had higher levels of each cognitive ability and of certain personality characteristics (e.g., agreeableness and openness), but many of the differences were only apparent among adults older than 50 years of age. Importantly, there was no evidence that the longitudinal change for nonreturning participants would have been different from that among the participants who did return.

DISCUSSION

The phenomenon of selective attrition is more complex than often assumed, and it may not necessarily limit the generalizability of longitudinal comparisons.

Evaluating the correspondence of different cognitive batteries

It is widely accepted that abilities are a meaningful level of abstraction for distinguishing among individuals with respect to their levels of cognitive functioning. However, relatively little is known about the extent to which different combinations of tests reflect the same cognitive abilities, or about the relation of cognitive abilities in one test battery with specific tests in another battery. Data from two cognitive batteries were analyzed to determine the correspondence of ability factors in the two batteries, and to evaluate the relative influence of cognitive abilities from one battery on the subtest scores in the other battery. Although the batteries involved different combinations of tests, correlations between the theoretically similar ability factors in the two batteries were very high (i.e., r > .84). Furthermore, with only a few exceptions, the primary influences on the subtest scores in one battery were from the theoretically relevant ability factor in the other battery.

Effects of first occasion test experience on longitudinal cognitive change

Effects of additional test experience on longitudinal change in 5 cognitive abilities was examined in a sample of healthy adults ranging from 18 to 80 years of age. Participants receiving experience with parallel versions of the cognitive tests on the first occasion had more positive cognitive change an average of 2.5 years later than participants performing only a single version of the tests on the first occasion. Importantly, these test experience effects were similar in adults of different ages, which implies that retest contributions to cognitive change are comparable among healthy adults between 18 and 80 years of age.

Within-cohort age-related differences in cognitive functioning

It is widely accepted that the level of cognitive functioning can be influenced by characteristics of the environment that change over time. Many developmental researchers have referred to these influences as cohort effects, and have used year of birth as the basis for determining cohort membership. Furthermore, age-related differences in cognitive functioning are sometimes assumed to be primarily attributable to cohort differences, which implies that differences between birth cohorts should be much larger than differences within birth cohorts. Comparisons of composite scores for five cognitive abilities in different people tested at different ages in different years revealed that within-cohort differences across ages were often as large as between-cohort differences across ages. These results lead to questions about the practice of relying on birth cohort to represent influences on cognitive functioning associated with temporal shifts in characteristics of the environment.

Selling points: What cognitive abilities are tapped by casual video games?

The idea that video games or computer-based applications can improve cognitive function has led to a proliferation of programs claiming to "train the brain." However, there is often little scientific basis in the development of commercial training programs, and many research-based programs yield inconsistent or weak results. In this study, we sought to better understand the nature of cognitive abilities tapped by casual video games and thus reflect on their potential as a training tool. A moderately large sample of participants (n=209) played 20 web-based casual games and performed a battery of cognitive tasks. We used cognitive task analysis and multivariate statistical techniques to characterize the relationships between performance metrics. We validated the cognitive abilities measured in the task battery, examined a task analysis-based categorization of the casual games, and then characterized the relationship between game and task performance. We found that games categorized to tap working memory and reasoning were robustly related to performance on working memory and fluid intelligence tasks, with fluid intelligence best predicting scores on working memory and reasoning games. We discuss these results in the context of overlap in cognitive processes engaged by the cognitive tasks and casual games, and within the context of assessing near and far transfer. While this is not a training study, these findings provide a methodology to assess the validity of using certain games as training and assessment devices for specific cognitive abilities, and shed light on the mixed transfer results in the computer-based training literature. Moreover, the results can inform design of a more theoretically-driven and methodologically-sound cognitive training program.

Robust cognitive change

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.

Increased prospective memory interference in normal and pathological aging: different roles of motor and verbal processing speed

This is a study on prospective memory (PM) and the PM interference effect in normal and pathological aging. One hundred and seven subjects, including 41 healthy young adults, 40 non-demented older adults and 26 patients with mild Alzheimer's disease (AD) participated in this study using a laboratory event-based PM task. PM task performance was comparable between the non-demented older and young adults, but impaired in the AD patients. The PM interference effect increased progressively from the healthy young adults, the non-demented older adults, to the AD patients. Path analysis revealed that the possible mechanism mediating the increased PM interference was the slow motor processing speed in normal aging, while it was the slow verbal speed in pathological aging. It is suggested that different neuropsychological mechanisms may underpin the affected performance of PM task in normal and pathological aging.

Does the direction and magnitude of cognitive change depend on initial level of 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.

Psychometric properties of within-person across-session variability in accuracy of cognitive performance

Although most psychological assessments are based on measures related to an individual's average level of performance, it has been proposed that measures of variability around one's average may provide unique individual difference information and have clinical significance. The current study investigated properties of within-person variability in measures of performance accuracy in a sample of more than 1,700 healthy adults. Contrary to what has been reported with measures of within-person variability in reaction time, measures of within-person variability in performance accuracy from different cognitive tests had weak correlations with one another, very low stability across time, and near-zero correlations with longitudinal change in cognitive abilities.

Using contextual analyses to examine the meaning of neuropsychological variables across samples of english-speaking and spanish-speaking older adults

The meanings of several target neuropsychological variables, including measures of executive functioning, were examined using contextual analysis across a sample of English-speakers and a sample of Spanish-speakers. Results of the contextual analysis, which examined the contributions of the latent constructs of memory, psychomotor speed, visual spatial ability, and knowledge and comprehension, to the target neuropsychological variables indicate that each of the target variables likely reflects the unique contribution of several reference abilities. These findings provide evidence that the neuropsychological variables are multi-dimensional. The patterns of relations were similar across the samples of English and Spanish speakers.

Measuring Working Memory Capacity With Automated Complex Span Tasks

Individual differences in working memory capacity are related to a variety of behaviors both within and outside of the lab. Recently developed automated complex span tasks have contributed to increasing our knowledge concerning working memory capacity by making valid and reliable assessments freely available for use by researchers. Combining the samples from three testing locations yielded data from over 6,000 young adult participants who performed at least one of three such tasks (Operation, Symmetry, and Reading Span). Normative data are presented here for researchers interested in applying cutoffs for their own applications, and information on the validity and reliability of the tasks is also reported. In addition, the data were analyzed as a function of sex and college status. While automated complex span tasks are just one way to measure working memory capacity, the use of a standardized procedure for administration and scoring greatly facilitates comparison across studies.

Does the level at which cognitive change occurs change with age?

Increased age in adulthood is associated with systematically more negative cognitive change, but relatively little is known about the nature of change at different ages. The present study capitalized on the hierarchical structure of cognitive abilities to investigate possible age differences in the level at which change operates. Reductions in the longitudinal associations between test scores when across-time relations were specified at different levels in the hierarchical structure were used to infer contributions to change from the level of abilities and from the level of a general factor. Although the pattern of influences varied across different cognitive abilities, the results revealed little or no age differences in the relative contributions to change from different levels in the hierarchy.

Natural and constrained language production as a function of age and cognitive abilities

Although it is often claimed that verbal abilities are relatively well maintained across the adult lifespan, certain aspects of language production have been found to exhibit cross-sectional differences and longitudinal declines. In the current project age-related differences in controlled and naturalistic elicited language production tasks were examined within the context of a reference battery of cognitive abilities in a moderately large sample of individuals aged 18-90. The results provide support for age-related increases in lexical sophistication and diversity at the discourse level, and declines in grammatical complexity in controlled and naturalistic contexts. Further, age-related decreases in facility with complex grammatical constructions in controlled sentence production were statistically independent of the cognitive abilities assessed in this project.

Are individual differences in rates of aging greater at older ages?

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 with 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 5 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 5 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.

How general are the effects of trait anxiety and depressive symptoms on cognitive functioning?

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.

Personality-cognition relations across adulthood

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.

What cognitive abilities are involved in trail-making performance?

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.

Influence of social desirability on age differences in self-reports of mood and personality

ABSTRACT Increased age has been found to be associated with differences in affect and personality that 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.

Correlates of level and change in the Mini-Mental State Examination

The goal of the current project was to determine (a) the cognitive abilities assessed by the Mini Mental State Examination (MMSE; M. F. Folstein, S. E. Folstein, & P. R. McHugh, 1975), (b) whether the same abilities are associated with MMSE performance among people of different ages, and (c) whether the same abilities are involved in changes within the same people over time. The authors therefore examined whether the initial levels of 5 cognitive ability constructs (vocabulary, reasoning, memory, space, and speed) predicted initial levels of MMSE performance and whether the initial levels or the changes in these 5 cognitive abilities predicted change in the MMSE performance. The major findings were that 3 cognitive constructs (vocabulary, reasoning, and memory) contribute to performance in the MMSE but that their respective contributions to the MMSE vary as a function of age and time. In particular, individual differences and change in the MMSE are primarily related to individual differences in reasoning among adults younger than about 70 years, whereas both initial level of MMSE performance and longitudinal change in MMSE performance primarily related to initial level and change in memory ability among adults older than 70 years. The results therefore imply that both the level of performance on the MMSE at a single point in time and the change in MMSE over time may represent somewhat different cognitive abilities at different ages.

Adaptation, expertise, and giftedness: towards an understanding of cortical, subcortical, and cerebellar network contributions

Current cortico-centric models of cognition lack a cohesive neuroanatomic framework that sufficiently considers overlapping levels of function, from "pathological" through "normal" to "gifted" or exceptional ability. While most cognitive theories presume an evolutionary context, few actively consider the process of adaptation, including concepts of neurodevelopment. Further, the frequent co-occurrence of "gifted" and "pathological" function is difficult to explain from a cortico-centric point of view. This comprehensive review paper proposes a framework that includes the brain's vertical organization and considers "giftedness" from an evolutionary and neurodevelopmental vantage point. We begin by discussing the current cortico-centric model of cognition and its relationship to intelligence. We then review an integrated, dual-tiered model of cognition that better explains the process of adaptation by simultaneously allowing for both stimulus-based processing and higher-order cognitive control. We consider the role of the basal ganglia within this model, particularly in relation to reward circuitry and instrumental learning. We review the important role of white matter tracts in relation to speed of adaptation and development of behavioral mastery. We examine the cerebellum's critical role in behavioral refinement and in cognitive and behavioral automation, particularly in relation to expertise and giftedness. We conclude this integrated model of brain function by considering the savant syndrome, which we believe is best understood within the context of a dual-tiered model of cognition that allows for automaticity in adaptation as well as higher-order executive control.

Influence of age on practice effects in longitudinal neurocognitive change

OBJECTIVE

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.

METHOD

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.

RESULTS

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.

CONCLUSIONS

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.

Influence of cognitive abilities and age on word recall performance across trials and list segments

The influence of cognitive abilities and age on multitrial word recall performance was examined for different list segments (i.e., first, middle, and last) and across trials by having 2497 participants ages 18-98 complete a multitrial word list test along with reference cognitive ability tests. As expected, higher episodic memory ability was associated with better recall on all list segments but with a smaller influence for the last items on the early trials. Performance improved across trials, but there were no relations of the fluid intelligence construct that might be postulated to be associated with effective strategy implementation with any of the recall measures. Advanced age was associated with lower levels of performance, but very few of the age relations were significant after the variation in the reference cognitive abilities was controlled for.

The role of activity engagement in the relations between Openness/Intellect and cognition

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.

Cognitive correlates of cross-sectional differences and longitudinal changes in trail making performance

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).

Selective review of cognitive aging

Research concerned with relations between adult age and cognitive functioning is briefly reviewed. The coverage is necessarily selective, and is organized in terms of five major questions. These are what abilities are related to age, how many distinct influences are contributing to the relations between age and cognitive functioning, do the differences between people increase with advancing age, what is responsible for the discrepancies between cross-sectional and longitudinal age comparisons of cognitive functioning, and what methods can be used to identify causes of age-related influences on cognition. Although definitive answers are not yet possible, quite a bit of information relevant to the questions is now available. Moreover, the existing information has implications for the design, analysis, and interpretation of cognitive and neuropsychological research concerned with aging.

Dealing with short-term fluctuation in longitudinal research

OBJECTIVES

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.

METHODS

Over 1,200 adults across a wide-age range performed different versions of cognitive tests on several sessions at each measurement occasion.

RESULTS

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.

CONCLUSIONS

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.

Does the meaning of neurocognitive change change with age?

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.

Is flanker-based inhibition related to age? Identifying specific influences of individual differences on neurocognitive variables

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.

Memory score discrepancies by healthy middle-aged and older individuals: the contributions of age and education

The aim of this study was to examine discrepancies between immediate/delayed recall and recall/working memory in middle-aged and older persons by age and education. Participants were 322 healthy individuals from the community who were stratified into three age and three education groups. Immediate and delayed recall distributions of WMS-III Logical Memory (LM) scores approximated normal curves, and LM savings scores showed a significant, but small, effect of age. LM (immediate, delayed) and Letter-Number Sequencing (LNS) discrepancies varied as a function of age and education. The difference between LM and LNS was not significant in the younger and less educated participants, but increased with age in the most educated group, and in the oldest group LNS exceeded LM (immediate and delayed). The results indicate deterioration in encoding and retrieval, rather than storage, with age, and show a differential, but small, effect of age and education on the memory measures. Working memory was resistant to age-related decline relative to immediate and delayed recall in the oldest, most educated group. Delayed recall-working memory discrepancy is relatively stable with age and education and may be a useful index of the onset of memory pathology across different ages and levels of education.

Confirmatory Factor Analysis and Multidimensional Scaling for Construct Validation of Cognitive Abilities

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.