The mean effect size model indicates that roughly half of the variance in personality on average can be attributed to genes (48%) and half to the environment (52%) which is consistent with previous research (Bouchard & Loehlin, 2001). However, there are significant age-trends across the lifespan. The full connected-linear model for heritability indicates substantial genetic influences very early in life, followed by a drop off in early childhood and plateau in middle age. Environmentality displays the opposite trend. However, not all of these slopes were necessary to account for the age trends present in the data. To represent the reduced models in a consistent tabular form, we have placed arrows in the table representing whether an earlier or later parameter estimate is applied to the age range. Adjacent parameter estimates represent alterations of the slope of the developmental trend. For example, the BIC preferred model of heritability indicated that only two slopes were required to properly describe the trend. One slope is for the ages of 0 to 15, and therefore an arrow has been placed in the b0–3 column
