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LONGITUDINAL PERSPECTIVES ON INTELLECTUAL DEVELOPMENT

Professor of Medical Psychology Department of Psychiatry and Behavioral Sciences Duke University School of Medicine Durham, NC

Developmental Influences on Adult Intelligence: The Seattle Longitudinal Study, by K. Warner Schaie. Oxford University Press, New York, 2005, 496 pp., $69.95 (cloth).

This volume on the Seattle Longitudinal Study (SLS) is the second of a series (see Schaie, 1996) summarizing findings from the SLS that not only expand the times of measurement but puts adult intellectual development in context of environmental, health, and family influences. The SLS began in 1956, is now approaching its 50^th birthday, and provides an invaluable guide to the intellectual history of research in the psychology of adult development and aging.

The study started with the following question: Why do cross-sectional studies of intelligence give a different picture of aging than longitudinal studies? In searching for answers, Dr. Schaie and his colleagues have made major contributions to developmental methodology and the substance of adult development.

For any longitudinal study to have "legs" the operationalization of the measurement is probably the most important decision—it must be state of the art and valid at first time of measurement and reliable enough to be repeated and allow for observation of true developmental changes while still providing information worth knowing 50 years later. Four key decisions have served the study and the field well: (1) an inspired decision that worked, Dr. Schaie's selection of Thurstone's Primary Mental Abilities for the basis of the SLS; (2) the choice of a random sample of participants in Group Health Cooperative as a study population; (3) the addition of new random samples for retest and sociocultural effects; and (4) the addition of a new, younger cohort at each time of measurement.

Each longitudinal follow-up sequence with its accompanying random samples from the same cohorts—at 7-year intervals—provided longitudinal as well as cross-sectional and time-lag sequences. In general, the main cognitive measures were repeated and additional measures were added partly in response to developments in the field, partly to appeal to study sections for continued funding, but mostly due to the intellectual curiosity of the study itself.

The data are presented in conceptual summaries with extensive tables and figures throughout the text and the appendices. As well as the cognitive sequences, there are also subpopulations of spouses, siblings, and recruited adult children and their siblings with new data on personality and behavior genetics (a veritable feast of data, presented for multiple audiences), means, proportions, and odds ratios. And then, even more exciting, are the preliminary studies on uses of the longitudinal cognitive data as predictors of dementia. It is impossible for me to imagine what the psychology of aging would be without the contributions from the SLS. But read it for yourself! Perhaps most impressive is the description of ongoing data collection. This is a study with a bright future as well as a stellar past.

Reference

• Schaie, K.W., (1996). Intellectual development in adulthood: The Seattle Longitudinal Study. New York: Cambridge University Press.

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Siegler, I. Search for Related Content PubMed Articles by Siegler, I.