Aged heterogeneity: fact or fiction? The fate of diversity in gerontological research.

Studies examining age-related changes typically report findings as age-based generalizations that neglect the phenomenon of variability in gerontological research. This paper examines the degree of attention given in 185 studies to individual differences and the empirical patterns of variability reported in those studies that present measures of dispersion. Measures of dispersion were reported in 43% of the gerontological studies reviewed and in 24% of the developmental studies. Overall, a majority of all gerontological studies presenting data reported increases in variability with increasing age (65%). This pattern was more pronounced in longitudinal studies than in cross-sectional ones.