Trajectories of infant positive emotion during the still face paradigm are associated with toddler temperament.

Guided by temperament and positive psychology theory, this study examined whether changes in infant expressed positive emotion were related to toddler temperamental positivity. At 4 months of age, infant expressions of positive, neutral and negative emotion were coded across the Still Face Procedure (SFP). Temperamental positivity was assessed at 24 months of age when toddlers participated in several tasks designed to elicit a range of emotions. Using a conditional multiphase nominal growth model that accommodated the structure of the SFP (free play, still face, and reunion episodes) and the categorical nature of the second-by-second repeated measurements of emotion, trajectories of infant emotion were derived and related to 24-month temperamental positivity. Results revealed that although temperamentally positive toddlers showed similar emotion trajectories overall to their peers differences emerged for the start of the still face episode. Temperamentally positive toddlers were more likely to show higher levels of positive (and lower levels of negative) emotion expression when mothers switched from free play to the still face episode. The data indicate that toddler temperamental positivity may be foreshadowed in early infancy by positive emotion expression immediately following an interactive rupture.