This study is the first to empirically demonstrate the genetic and environmental stability trends of personality across nearly the entire lifespan. By aggregating data and applying meta-analytic techniques, we have provided a provocative picture of personality development. We obtained data from 24 studies that sampled more than 40,000 individuals who ranged in age from infancy to old age. Our approach, however, was not without limitations. First, we chose to apply random-effects connected-linear spline models to describe the age-trends in the data. These models have the advantage of being able to detect discontinuities in trends. For example, we found that increasing phenotypic stability appears to stall in early childhood. There are two interpretations of this finding. Either phenotypic stability truly stalls during this developmental period, or the model was overspecified and simply picked up on noise in the data that was not meaningful. To counteract this possibility, we have provided results from a number of different modeling approaches. By providing the most complex connected-linear spline model, the trends can be examined with the greatest flexibility. Alternatively, the continuous exponential trend provides
