Longitudinal Research

Longitudinal means lengthwise; a longitudinal study deals with the growth and change of an individual or group over time. The Handbook of General Psychology differentiates between cross-sectional, longitudinal, and clinical research. In the field of psychology, “the longitudinal method consists of measuring the same individuals at different intervals over a period of time. Some longitudinal studies are relatively short-term, others are impressively long-term: thirty or more years” (Wolman 1973: 864–65). An example of an extremely long-term study is Lewis Terman's “Life Cycle Study of Children with High Ability,” which he started in 1921 and finished in 1991.

Scholars have used other terms besides longitudinal research to describe these studies. The Danish sociologist Kaare Svalastoga preferred “sequential”; the American psychologist John Dollard described life history as the ...