Normative personality change over 40 years was shown in 2 longitudinal cohorts with hierarchical linear modeling of California Psychological Inventory data obtained at multiple times between ages 21-75. Although themes of change and the paucity of differences attributable to gender and cohort largely supported findings of multiethnic cross-sectional samples, the authors also found much quadratic change and much individual variability. The form of quadratic change supported predictions about the influence of period of life and social climate as factors in change over the adult years: Scores on Dominance and Independence peaked in the middle age of both cohorts, and scores on Responsibility were lowest during peak years of the culture of individualism. The idea that personality change is most pronounced before age 30 and then reaches a plateau received no support.

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The precise, quantitative portrayal of intraindividual change is a key goal of developmental researchers. Research designs particularly appropriate to selected aspects of this goal are multivariate, replicated, single‐subject, repeated measures (MRSRM) designs. Data collected with these designs may be factor analyzed with P‐technique factor analysis to elucidate, for each individual studied, patterns of systematic change. The nature of the factor patterns obtained for each individual can then be compared across individuals to determine the relative idiosyncrasy or generality of patterns of change. This paper extends an earlier review (Luborsky & Mintz, 1972) of studies using multivariate, single‐subject, repeated measures designs and P‐technique factor analysis. The emphasis here is on both more recent studies and the value of subject replication in creating a confluence of idiographic and nomothetic approaches to the study of behavior and behavioral development across the lifespan.

Six aspects of personality were examined for a sample of 211 individuals across either a 30- or 40-year time span. Latent curve analyses found an underlying pattern of lifetime change for self-confidence, cognitive commitment, outgoingness, and dependability. An underlying pattern of lifetime stability was found for assertiveness. No shared systematic underlying pattern could be fit to individuals' lifetime trajectories for warmth. Although individuals shared a single underlying pattern of change or stability for 5 of the 6 dimensions of personality considered here, they also showed differences in the degree and direction of personality change.

Developmental paths of psychological health were examined for 236 participants of the Berkeley Growth Study, the Berkeley Guidance Study, and the Oakland Growth Study. A clinician-reported aggregate index, the Psychological Health Index (PHI), based on California Q-Sort ratings, was created for subsets of participants at 14, 18, 30, 40, 50, and 62 years of age. Latent curve analysis was then used to explicate the life span development of psychological health. Psychological health development could be successfully modeled via 2 piecewise latent growth curves. Psychological health appears to be stable in adolescence and to steadily increase from 30 to 62 years of age. A moderately strong positive correlation between the 2 developmental curves indicates that those with greater psychological health in adolescence show more improvement in adult psychological health tend to also. Results illustrate the value of the PHI and the power of latent curve analysis to explicate longitudinal stability and change.