Roberts and DelVecchio’s (2000) meta-analysis treated time lag between measurement occasions as a confound to be controlled. It is nearly a truism that traits are less stable over longer periods of time. Fraley and Roberts (2005) specifically emphasized this point by re-analyzing the data with variation in time interval, rather than age of the participants, as the primary independent variable predicting differential stability. They detected time-based decay that varied depending on the initial age of assessment. In order to avoid potential confounding of age- and time lag- effects, we will control for the linear effect of time lag in all analyses. However, the emphasis of the current meta-analysis is on lifespan age-based trends. In order to confine the scope of this article, we will not report results of analyses that explore more nuanced nonlinear functions of time-lag (importantly, results that control for nonlinear effects of time-lag are nearly identical to those presented here).
