Two complementary studies examined the unique contribution of positive emotion to development. The studies considered different ages, measured emotion in different contexts, and utilized different statistical methodologies, thereby answering unique questions about the development of children’s positivity, the relationship between mothers’ and children’s positivity, and the relationship between positivity and later behavioral outcomes.

Study 1 tested a conceptual model, examining the sequelae of positivity within the mother-child relationship. During toddlerhood, children spend the majority of their time at home, making relationships between mothers’ and children’s positive emotion particularly relevant.  Concurrent bidirectional relationships at both 24 and 36 months between children’s and mothers’ positivity were found.  Mothers’ and children’s positivity at 24 months predicted their own positivity at 36 months, but cross-lagged pathways were not significant. Mean differences in positivity were not found.  Both individuals’ positivity at 36 months predicted later social competence, but only maternal positivity predicted internalizing and externalizing behaviors.  Results of an alternative model, which included mothers’ negative emotion, were consistent, except mothers’ positive emotion no longer predicted internalizing behavior.  Thus, positive emotion early in development predicts both later positivity and important developmental outcomes, over and above mothers’ negative emotion.

Study 2 identified two trajectory groups of children’s positive emotionality from 24 months to 5th grade in childcare and school.  This is the first study to longitudinally track positive emotion with peers from toddlerhood through the school years. Studying positive emotion outside of mother-child interactions permitted Study 2 to test the cross-context influence of early maternal positivity on children’s positivity.  The first, larger group identified started low in positivity and increased over childhood.  The second, smaller group began high in positivity and decreased.  These groups were significantly different in positivity at all time points.  For both groups, tests of mean differences at consecutive ages indicated stability during toddlerhood and the school years, but change during preschool. High maternal positive emotion at 24 months predicted membership in the second group (high/decreasing), and membership in this group predicted greater social competence in 6th grade.  In conclusion, positive emotion is distinct from negative emotion and contributes unique information about children’s behavior.