Biomedical subjects
Publications and source records attributed to K W Schaie.
The impact of methodological changes on gerontology is illustrated by discussing the example of the age-cohort-period problem as an innovation in research design, and examining the case of confirmatory factor analysis as an illustration of how methodological innovation informs theory.
The interrelationship of measures of rigidity-flexibility and of psychometric intelligence is examined. The latent factors of Attitudinal Flexibility, Motor-Cognitive Flexibility, and Psychomotor Speed are derived from the Test of Behavioral Rigidity, and factors of Inductive Reasoning, Spatial Orientation, Verbal Ability, Numeric Ability, Verbal Memory, and Perceptual Speed are derived from the Thurstone Primary Mental Abilities Test and the Educational Testing Service Kit of Factor-Referenced Tests. The data base in this study comes from the fifth wave of the Seattle Longitudinal Study (N = 1,628; age range, 22-95 years). The Rigidity-Flexibility factors were found to be independent of the cognitive domain. Also, longitudinal stability of the factor structure of the rigidity-flexibility domain was confirmed for 837 participants tested in both 1977 and 1984.
Results are presented from cross-sectional and longitudinal analyses of data from the Test of Behavioral Rigidity for 3,442 subjects over the age range from 22 to 84 years. Data are presented on the Behavioral Flexibility, Attitudinal Flexibility, and Social Responsibility questionnaire scales, as well as on performance score measures indexing Associational Flexibility, Instructional Set Flexibility, Copying Speed, and Associational Speed. Data on these scales were obtained for 5 samples examined 7 years apart (1956, 1963, 1970, 1977, and 1984). These data permit analyses of birth cohort differences and rate of change within the same individuals, as well as successive samples drawn from the same cohort over as long as 28-year periods. Results of the analyses confirm the presence of substantial generational differences, with generally only limited change over time within cohorts.
We now return to the sets of hypotheses formulated in the introductory section to explore how the findings reported above bear on these propositions. Our first hypothesis dealt with whether family similarity could be observed in adulthood and whether there were differing ability patterns in such similarity. Significant family similarities were observed for our total sample for all ability measures, except Perceptual Speed, and for the cognitive style measures. The magnitude of correlations for the ability measures are comparable for those found between young adults and their children (DeFries et al., 1976). Similar to the DeFries study, we also found differences in resemblance across subsets. For example, same gender pairs showed higher correlations on Verbal Meaning, Number, and Word Fluency but opposite-gender pairs on Spatial Orientation, Inductive Reasoning, and Motor-Cognitive Flexibility. Also, greater similarity was found between mother-offspring pairs than father-offspring pairs on Inductive Reasoning and Psychomotor Speed. Moreover, higher parent-offspring correlations were found for daughters than for sons, suggesting at least the possibility that females may experience greater shared environmental influences than males. Our first hypothesis also argued for the possible effect of early shared environment upon offspring performance on Verbal Meaning and Word Fluency. After age adjustment, these were indeed the abilities that showed the highest parent-offspring similarity. Our second hypothesis proposed that if shared environmental influences are relatively unimportant in adulthood, then similarity within parent-offspring pairs should remain reasonably constant in adulthood across time and age. Our examination of this issue with a longitudinal sample ranging over a 21-year period strongly supports this proposition for all of those variables that displayed significant parent-offspring correlations. Indeed, parent-offspring correlations measured at approximately the same age of parent and offspring and when those ages were 20 years apart had similar magnitudes. The third hypothesis asked whether family similarity would decrease with age because of the increasing amount of nonnormative, nonshared environment expected as adult life progresses. Counterintuitively, no such decrease in similarity could be observed. Indeed, for two variables there was evidence for increasing similarity as a function of offspring age. This finding makes good sense for our Perceptual Speed variable. Most of our younger offspring typically have not yet experienced age-related decline on this variable, whereas some of their parents have. Both older offspring and parents may have experienced sufficient decline so that once again their observed similarity is increased.(ABSTRACT TRUNCATED AT 400 WORDS)
The results of psychometric analyses of the Metamemory Questionnaire (MQ; Zelinski, Gilewski, & Thompson, 1980), developed to evaluate perception of everyday memory functioning, are presented for a sample of 343 men and 435 women aged 16 to 89. Exploratory factor analysis yielded 4 correlated factors--General Frequency of Forgetting, Seriousness of Forgetting, Retrospective Functioning, and Mnemonics Usage--which accounted for 36.7% of the variance in responses to the MQ. Factor structure was invariant across age groups (16-54 vs. 55-89 years), 2 independent samples, and over 3 years. Because some of the original MQ scales did not load on the factors, only 64 of the original 92 items were retained for inclusion in the Memory Functioning Questionnaire (MFQ). Internal consistency of MFQ scores is high. The MFQ is therefore reliable for evaluating memory self-appraisals.
Cross-sectional data on age differences in perceptual speed are presented from the Seattle Longitudinal Study for the age range 22-91 years (N = 1,620, first assessed in 1977; N = 628, first assessed in 1984). In addition, 838 subjects were followed over the 7-year interval. Markers of perceptual speed were the Identical Pictures and Finding A's tests from the ETS Kit of Factor-Referenced Tests. Significant age differences, age changes, and cohort differences were found at both observed variable and latent construct levels. Cross-lagged correlations examine the role of perceptual speed in predicting later performance on other abilities (Verbal Meaning, Inductive Reasoning, Spatial Orientation, Number, and Word Fluency). When perceptual speed is partialled out of scores for these abilities, aging effects are reduced markedly for all abilities, but least for Spatial Orientation and Inductive Reasoning.
After a review of findings from the Seattle Longitudinal Study of adult cognitive development, this paper discusses the application of event history analysis, a technique pioneered by sociologists, to data involving changes of states in individual behavior related to human aging. The dependent variable of interest for psychologists and other developmentalists should be the age (calendar or functional) at which the event occurs rather than its index in historical time. Using occurrence of significant decline in cognitive abilities as an exemplar, hazard functions are presented that allow the assessment of risk for future decline, as well as the prediction of the calendar age when individuals can expect cognitive decline under alternative assumptions.
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We analyzed data on psychometric intelligence from the Seattle Longitudinal Study, simultaneously estimating longitudinal factors, their covariance structure, and their mean levels. Data on five Thurstone Primary Mental Abilities subtests were available for 412 adults, ages 22-70 at first test, who were tested three times at 7-year intervals. A previous longitudinal factor analysis had shown high stability of individual differences (covariance stability) in general intelligence for three adult age groups. We extended that model to estimate factor means. All three age groups showed high levels of covariance stability, but differed sharply in their mean profiles. The young group showed increasing levels of general intelligence, the middle-aged group had stable levels of intelligence, and the old group showed salient, approximately linear, decline. The patterns of stability in middle-age, followed by mean decline and high covariance stability in old age, suggest a normative developmental transition from a stability pattern to a decline pattern of general intelligence, with the inflection point occurring somewhere around age 60.
Surviving members of the Berkeley Older Generation Study were interviewed and tested with the Wechsler Adult Intelligence Scale in 1969-1970 and again in 1983-1984, when subjects' ages ranged from 73 to 93. Health was assessed by self-reports at both measurement periods. Although many individuals showed some decline in intellectual functioning, substantial individual differences were apparent at all age levels. More than one half of the subjects showed no reliable change, and a minority showed a reliable increase in verbal scores. The role of self-reported health has increasing importance in the maintenance of intellectual functioning in advanced old age.
This study compared the intellectual and personality functioning of continuing participants in a longitudinal study with individuals who were lost from the panel after at least 7 years of involvement. Based on their reason for discontinuation, participants who were lost to the panel were categorized into three attrition groups: deceased, ill, and voluntary dropouts. When the performance of these groups prior to leaving the study was compared with that of the continuing participants, no general differences were found. However, specific differences were revealed, particularly on crystallized-type intellectual abilities and the personality factors. Participants who were lost due to illness or death had functioned at the lowest levels of the four groups prior to attrition. These effects varied by age. In late middle age, ill participants functioned at the lowest levels, whereas in old age, participants who subsequently died scored lowest of the four groups prior to attrition. Individuals who had voluntarily discontinued participation in the study most closely resembled the continuing participants, particularly in late middle age. The results indicate that performance effects associated with continued participation vary by age, the intelligence or personality factor being considered, and the reason for loss of the participant. Furthermore, they suggest that loss of participants from a longitudinal panel does not inevitably bias the validity of developmental findings.
We report results of the first empirical test, as far as we know, of the assumption of structural invariance of latent constructs from pretest to posttest in cognitive training research on the elderly. In all, 401 participants in the Seattle Longitudinal Study, over 62 years old, received a 5-hr test battery at pre- and posttest that included 16 ability tests, marking the five primary abilities of Spatial Orientation, Inductive Reasoning, Numerical Ability, Verbal Ability, and Perceptual Speed. A total of 229 of our subjects received 5 hr of individual training on either Spatial Orientation or Inductive Reasoning. Restricted factor analysis with the LISREL algorithm tested the hypothesis of measurement equivalence across test occasions, separately for the control subjects and for each of the training groups. When ability-specific cognitive training intervenes, no structural change is observed for abilities not subject to intervention. However, slight shifts occurred in the optimal regression weights for the different markers for the training target abilities.
We address two questions of central interest in adult intellectual development: the equivalence of psychometric tests' measurement properties at different ages, and the stability of individual differences in intelligence over time. We performed a series of longitudinal factor analyses using the LISREL program to model longitudinal data from Schaie's Seattle Longitudinal Study. The results indicate complete invariance in the loadings of five subtests of Thurstone's Primary Mental Abilities battery on a general intelligence factor. Individual differences in general intelligence were highly stable over 14-year epochs, with standardized factor correlations averaging about .9 between adjacent 7-year testing intervals. These results indicate that most individuals in this relatively select longitudinal sample maintained their relative ordering in intelligence.
We examined the effects of cognitive training with elderly participants from the Seattle Longitudinal Study. Subjects were classified as having remained stable or having declined over the previous 14-year interval on each of two primary abilities, spatial orientation and inductive reasoning. Subjects who had declined on one of these abilities received training on that ability; subjects who had declined on both abilities or who had remained stable on both were randomly assigned to the spatial orientation or inductive reasoning training programs. Training outcomes were examined within an ability-measurement framework with empirically determined factorial structure. Significant training effects, at the level of the latent ability constructs, occurred for both spatial orientation and inductive reasoning. These effects were general, in that no significant interactions with decline status or gender were found. Thus, training interventions were effective both in remediating cognitive decline on the target abilities and in improving the performance of stable subjects.
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The present study investigated the effects of three conditions of pretest activity on the intellectual performance of 90 middle aged (50-61) and elderly (62-72) individuals. The Primary Mental Abilities Test was presented under three pretest conditions: physical, mental and physical, and no activity. Multi- and univariate analyses revealed significant age (or cohort) and sex differences in intellectual performance, but no significant pretest treatment effects. These results, when combined with similar recent findings of other investigators, indicate that pretest activity effects are less powerful than some widely cited previous research has suggested.
The relation of intelligence and competence is discussed and external validity issues are examined for the dimensions of settings, measurement variables, treatment variables and experimental units. It is argued that external validity across situations and life stages cannot be obtained for any single measure of intellectual ability. External validity problems are exacerbated beyond young adulthood since single criterion goals comparable to that of educational aptitude in work with the young are not available, and tasks do not retain ecological validity when the situational context of the individual under study changes due to developmental progression and idiosyncratic modification of individual life situation and roles. External validity in adulthood must therefore be addressed by examining task-by-person-by-situation interfaces separately for different life stages and across cohort groupings. A major test construction and validation program is outlined, and examples are given showing how some of the aspects of such a program can be operationalized.