Glee in threes: Positive affect synchrony in parent-infant triads is moderated by maternal hair cortisol and parenting stress.

Background: Positive affect synchrony, or the reciprocal exchange of positive affect during free play, can scaffold infants' socioemotional development. However, parental stress may compromise the expression and exchange of positive affect within families. The current study assesses whether parenting stress and hair cortisol are associated with positive affect synchrony during a triadic play interaction.