Figure 1.

Expected mean trajectories for mother- and nursery-reared animals and corresponding 95% confidence intervals of the expected trajectories of individual animals within these groups for Orientation (1a), State Control (1b), and Motor Activity (1c). The mean trajectories for each group are displayed using bold lines and 95% intervals of the within-group, between-animal differences in change are displayed by the shaded areas. Estimates are based on the validation sample. The variances of the random intercept and slope correspond to the between-animal variability in the factor scores at 7 days of age and in the linear rates of change, respectively. Assuming that the random effects are normally distributed, then approximately 95% of the individual intercepts and slopes are expected to range about their respective mean values by ± 1.96*SD of the corresponding random effect. For instance, the mean intercept of Orientation (1a) for nursery-reared animals was equal to 0.35 and the SD of the random intercept was 0.41. It follows that approximately 95% of intercepts for nursery-reared animals are expected to range from 0.35 ± 1.96*0.41 or −0.45 to 1.15. These values are shown for each of the three factors by the shaded areas. The lightest shading represents expected animal-level trajectories for the mother-reared animals and the darkest shading represents expected trajectories for the nursery-reared animals. The overlap between groups is represented by the medium shade of gray. As shown, there is overlap between groups in the expected range of the individual-level trajectories for each other the three factors. Thus, even though there were statistically significant differences in the mean factor scores between groups, there was considerable overlap in the expected trajectories of the individual animals.