Various research designs employed in developmental psychology for the investigation of maturational and aging effects are examined. It is found that discrepancies and contradictions in the conclusions derived from cross-sectional and longitudinal studies are consequences of the violation of assumptions implicit in these research designs. The conventional methods are shown to be special cases of a general model for research on behavior change over time. The properties of the general model are explicated and the assumptions for the customary designs are reviewed in the light of these properties. The complete model requires consideration of the components of age, time and cohort differences in the identification of developmental change. Both the longitudinal and cross-sectional methods in this context require strong assumptions which can rarely be met. New research strategies are therefore suggested which involve the optimal combination of cross-sectional and longitudinal methods into sequential designs. Such designs and their assumptions are presented both for the independent random sampling and the repeated measurement cases.
A program of research is summarized that represents the author's lifelong efforts to understand the adult life course of intellectual abilities. The Seattle Longitudinal Study has assessed mental abilities in more than 5,000 adults and has followed some for as long as 35 years. Integrative findings are provided on patterns and magnitudes of age changes, cohort differences, factor structure of mental abilities, antecedents for individual differences in aging trajectories, and interventions designed to remediate cognitive aging effects.
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.
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