Do Non-shared Environmental Influences Persist Over Time? An Examination of Days and Minutes

Non-shared environmental influences show only minimal stability over time prior to adulthood. The long assessment lags (typically 3–5 years) that characterize most longitudinal twin studies, however, make it difficult to interpret these results. To more rigorously evaluate non-shared environmental stability prior to adulthood, we fitted biometric correlated factors models to (1) seven consecutive days of self-reported negative and positive affect in 239 twin pairs aged 16–25 years and (2) seven consecutive minutes of observer rated warmth and control in 687 twin pairs aged 6–10 years. We then empirically examined patterns of etiologic stability over time using a mixed effects analog to the one-way ANOVA. Genetic and shared environmental correlations were found to be highly stable over both days and minutes. By contrast, non-shared environmental correlations decreased monotonically with increasing lag length, and moreover, were small-to moderate in magnitude when examining intervals longer than a few minutes. Such findings imply that the non-shared environment may be comprised primarily of transient and idiosyncratic effects prior to adulthood.