Mother–infant mutual eye gaze supports emotion regulation in infancy during the Still-Face paradigm

•Mutli-linear model can be used to better understand synchronicity of mother–infant interactions.•Mutual eye gaze between a mother and her infant enhances emotional regulation.•Infant's use of self-regulation strategies improves emotional regulation during a stressful situation. This study was designed to examine the sequential relationship between mother–infant synchrony and infant affect using multilevel modeling during the Still Face paradigm. We also examined self-regulatory behaviors that infants use during the Still-Face paradigm to modulate their affect, particularly during stressors where their mothers are not available to help them co-regulate. There were 84 mother–infant dyads, of healthy full term 4 month old infants. Second-by-second coding of infant self-regulation and infant affect was done, in addition to mother–infant mutual eye gaze. Using multilevel modeling, we found that infant affect became more positive when mutual gaze had occurred the previous second, suggesting that the experience of synchronicity was associated with observable shifts in affect. We also found a positive association between self-regulatory behaviors and increases in positive affect only during the Still-Face episode (episode 2). Our study provides support for the role of mother–infant synchronicity in emotion regulation as well as support for the role of self-regulatory behaviors in emotion regulation that can have important implication for intervention.