Longitudinal Data Sets: Evidence for Ontogenetic Development or Chronicles of Cultural Change

Limitations of single‐cohort data sets are discussed, and their pitfalls are illustrated by means of a multiple‐cohort study of the cognitive ability of spatial orientation. The questions of gender differences in age changes and experimental attrition are further illustrated by examining a study of the questionnaire‐derived personality traits of social responsibility. Finally, implications are suggested for the internal and external validity of inferences drawn from analysis of the Ginzberg‐Yohalem data set.