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This chapter presents an overview of the phenomena of adult cognitive development. It lays out the reasons why intelligence in adulthood should be studied by giving a brief history of the study of adult intelligence. It points out that intellectual competence attains increasing importance from middle adulthood onwards, when level of intellectual competence may determine job retention. It discusses whether independent living within the community remains possible in later life, and considers maintenance of control over financial decision making. A conceptual model is then given to tackle the developmental influences that have an impact on the life course of cognition. The model provides the rationale for the various influences related to cognitive development. An account is then given of the history and objectives of the Seattle Longitudinal Study.

This chapter presents the database for the Seattle Longitudinal Study and details the study participants and the measurement battery. The chapter also discusses, in addition to the cognitive ability measures, the neuropsychological assessment battery; measures of cognitive style; everyday problem solving; self-reported cognitive change; lifestyles, health status, health behaviors, and the subjective environment; as well as measures of personality traits and attitudes.

This chapter reviews the central core of the Seattle Longitudinal Study: the results from the longitudinal inquiries. The longitudinal studies consist of six seven-year follow-ups, five fourteen-year follow-ups, four twenty-one-year follow-ups, three twenty-eight-year follow-ups, two thirty-five-year follow-ups, and one forty-two-year follow-up. The longitudinal database is integrated to provide estimates of age changes based on the largest available number of study participants for each age interval. To permit comparison with the cross-sectional findings, the base mean-level estimates were set to the observed average values across all cohorts for participants tested at age 53 (the average age of the total sample). The average intra-individual age changes aggregated across all cohorts for which each age interval is available were then cumulated and added to or subtracted from these base values. These predicted values are provided for the total sample as well as being separately by gender.

This chapter summarizes several methodological issues, including certain research design and analysis paradigms, related to the Seattle Longitudinal Study. The discussion begins with a brief exposition of the relationship between cross-sectional and longitudinal data within the context of the general developmental model, followed by a presentation of the rationale for a variety of simple and sequential schemes for data acquisition and analysis. The problems of internal validity of developmental studies and designs for the measurement and control that plague developmental studies are explored. The chapter ends by exploring the relationship between observed measures and latent (unobserved) variables, and how confirmatory (restricted) factor analysis can be applied to assess construct equivalence across cohorts, age, and time in the study of developmental problems.

This chapter reports findings with respect to the trait of social responsibility and describes the work on personality traits derived from the seventy-five Test of Behavioral Rigidity (TBR) questionnaire items included in the Seattle Longitudinal Study. Preliminary data on recent work relating the TBR-derived personality factors to the NEO (Neuroticism, Extraversion, Openness) are presented. New work on the Center for Epidemiologic Studies-Depression Scale (CES-D) questionnaire used as a subjective measure of depression in the SLS participants older than 60 years is described.

This chapter describes some of the methodological studies that were conducted as part of the Seattle Longitudinal Study. The discussion mentions the shift from a sampling-without-replacement paradigm to one that involved sampling with replacement, as well as the issue of the aging of tests and results from an investigation designed to determine whether switching to more recently constructed tests would be appropriate in the context of the longitudinal study (1975 collateral study). The possible effect of repeated measurement designs in understating cognitive decline is considered and analyses that adjust for practice effects are presented. The issue of structural equivalence across cohorts, age, time, and gender is also explored.

This chapter discusses the effects of health on the maintenance of intellectual functioning, the role of health behaviors, the effects of cognitive abilities as predictors of physical health, mortality, and medication use, as well as the role of perceptions of social support on health. A series of studies is described that relates the role of disease and intellectual functioning in the Seattle Longitudinal Study. The first study implicated cardiovascular disease as associated with earlier onset of decline of intellectual functioning. The second study, concerned with the structural relationship between disease processes and maintenance of intellectual functioning, also implicated cardiovascular and musculoskeletal conditions as leading to excess risk for cognitive decline.

Although the Seattle Longitudinal Study was designed to focus on cognitive changes in normal community-dwelling populations, it is inevitable that a prospective study of aging will eventually include in its successive follow-up cycles individuals who are beginning to show cognitive impairment and eventually may develop full-blown symptoms of dementia. This chapter reports some initial findings on the apolipoprotein E genetic marker of dementia as it relates to cognitive decline. Studies involving the neuropsychological assessment of a community-dwelling sample of older adults who have not previously been identified as suffering from cognitive impairment are described, along with the extension analyses that link the clinical measures with the psychometric battery for the study of normal aging. The chapter ends by analyzing studies that obtain postdicted estimates of earlier performance on the neuropsychological measures and speak to the possibility of early detection of risk for cognitive impairment.

This chapter presents conclusions from the Seattle Longitudinal Study. The lessons learned are reviewed in the context of the five questions considered in this book regarding the life course of intellectual competence, and the conclusions reached from interventions in the normal course of adult cognitive development are discussed. The findings from studies designed to learn more about adult cognition in a developmental behavior, genetic, and/or family context are described, along with findings from extensions into identifying the genetic and environmental influences that shape adult intellectual development. The chapter ends by providing information on how to access certain limited data sets from the SLS that are being made available for use by qualified researchers and college teachers for secondary analyses or instructional purposes.

This chapter reports the results of the cognitive intervention studies and their long-term follow-up and replication with new cohorts, as part of the Seattle Longitudinal Study. These studies lead to the conclusion that, for many persons, cognitive decline in old age may be a function of disuse rather than deterioration of the physiological substrates of cognitive behavior. A brief five-hour training program on the abilities of Inductive Reasoning and Spatial Orientation involving individual tutorials was designed to improve the performance of participants above the age of sixty-four years. Participants were assigned either to training in the ability on which they had declined or randomly to one of the two training conditions if they had declined or remained stable on both abilities.

This chapter describes analyses on the relation between personality and cognition. Included in the analyses are three different subsets from the Seattle Longitudinal Study. Interestingly, it was found that there are modest but significant concurrent relationships between personality trait measures and ability construct that account for up to 20% of shared variance. The personality dimensions that were most substantively related to high performance on cognitive ability factors were high untroubled adequacy, low conservatism, and low group dependency from the thirteen personality factors measure and high scores of Openness on the NEO Personality Inventory. There is moderate stability across time for the personality measures which is fairly comparable with the stability found in much of the personality literature.

This chapter presents data from the Seattle Longitudinal Study on the similarity of perceptions about family environments of parents and their adult offspring and the similarity in such perceptions of adult siblings reported in adulthood. Perceptions about family environments are considered both with respect to the family of origin (i.e., the family setting experienced by the study participants when they lived with their own parents) and with respect to the current family (i.e., their family unit at the time these data were collected). Included in this chapter also are analyses of the relation of perceived family environments to reported current intensity of contact between parent and offspring and between sibling pairs.

This chapter describes the pilot studies that led to the selection and validation of the measures used in the Seattle Longitudinal Study. The 1956 baseline study is presented and its findings are compared with the six cross-sectional replications. For purposes of an orderly presentation, the basic cognitive battery that is common to all study cycles is analyzed. Data for the fifth, sixth, and seventh cycles for the extended cognitive battery and the practical intelligence measures are then presented. Finally, the cross-sectional findings for the measures of cognitive style (Test of Behavioral Rigidity, TBR) are discussed.

This chapter reports findings regarding cohort and period differences in cognitive abilities as well as on other variables included in the Seattle Longitudinal Study. Here, expanded operational definitions are provided for the computation of cohort and period effects and cumulative findings through the seventh study cycle are expanded and updated. Possible applications of the period effect estimates are considered. An example is provided of how corrections for cohort and period effects can be applied to adjust longitudinal estimates to obtain increased generalizability.

This chapter gives an account of family studies of intellectual abilities in adulthood designed to consider similarities in adult parent-offspring and sibling pairs as well as similarity in married couples. Of particular interest is new material on changes in the rate of cognitive change across biologically related generations. Married couples were studied for as long as twenty-one years. They showed significant initial within-couple correlations on verbal meaning, inductive reasoning, and word fluency, and social responsibility, and on the Index of Educational Aptitude, even when age and education were controlled. Spousal similarity increased by length of marriage on verbal meaning, and attitudinal flexibility, and on the Index of Intellectual Ability.

This chapter presents evidence on the distinctiveness of cognitive styles of motor-cognitive flexibility, attitudinal flexibility, and psychomotor speed from the domain of psychometric intelligence as measured in the Seattle Longitudinal Study. The concurrent and predictive relationships for the domains utilizing the cognitive style and core battery primary mental ability variables over the age ranges studied are then considered, along with similar data for the latent ability constructs over the seven- and fourteen-year periods. The predictive direction is identified to lead from the cognitive style measures to the ability measures of verbal meaning, number, and word fluency in the core battery and to the latent construct measures of verbal and numeric ability.

The Life Complexity Inventory (LCI) has been used since 1974 to characterize the microenvironment of participants in the Seattle Longitudinal Study. Early analyses of this instrument identified eight lifestyle factors that were related to measures of intellectual abilities. Low-to-modest positive correlations were found between amount of leisure activity and levels of cognitive functioning. Positive lifestyle characteristics were also correlated with high levels of cognitive functioning, with the dimensions of prestige, social status, and work characteristics showing the highest correlations. This chapter discusses lifestyle variables that affect intellectual functioning. Family similarity in lifestyles was examined for parent-offspring and sibling dyads, along with the effects of work characteristics and retirement on cognitive functions.

This chapter examines the accuracy of adults' perceptions with regard to an issue that is of increasing concern with age: whether our intellectual abilities are actually declining. These concerns were investigated by evaluating the accuracy of participants' assessment of intellectual change over seven years. Subjective report of performance change was compared with actual observed change over seven years. The seven-year retrospective data were replicated for a second seven-year period in 1991 and the stability of the congruence types identified in this study over a fourteen-year period was investigated. Judgments of short-term change after repeated testing and training interventions spanning a four-week period for three different training occasions were also evaluated.

This book presents the history, results, and latest data from the Seattle Longitudinal Study (SLS), first launched in 1956 to investigate various aspects of intellectual development from early adulthood to old age in a random sample of 500 individuals aged 25–95 years. The SLS examined whether intelligence changes uniformly throughout adulthood, or whether there are different life-course-ability patterns; the patterns and magnitude of generational differences; the factors that account for individual differences in age-related change in adulthood; and whether the intellectual decline that increases with age can be reversed by educational intervention. This book updates and integrates data collected through 2005 and expands work on biomarkers of cognitive aging, along with the link between changes in cognition and brain structure. It includes three new chapters dealing with health behaviors and intellectual functioning, biological influences on cognitive change, and prediction of individual cognitive decline. This introductory chapter discusses the origin, history, and objectives of the SLS and explains the rationale for studying intelligence in adulthood. It also describes the theoretical framework for understanding intellectual development in adulthood.