A different story emerged for genetic and environmental stability. Genetic stability only required two slopes. This model indicated that genetic stability was high in infancy (b0 = .553, p < .001), and increased linearly until age 30 (b0–30 = .016, p < .001). At this age, genetic stability reached unity and remained nearly perfectly stable across the remainder of the lifespan. The preferred model for environmental stability was slightly more complex. In infancy, environmental stability rises quickly (b0–3 = .176, p < .001), and then continues to rise at a slow, steady rate over the majority of the lifespan (b3–60 = .006, p < .001). Following age 60, environmental stability appears to decrease. However, this decrease appears to be attributable to measurement error. The age-trends for measurement error corrected environmental stability displays a somewhat jagged trend (i.e., rises in infancy, declines in childhood, and then rises in adolescence), but following age 30, environmental stability remains constant (b30–90 = .002, p = .22).
