We investigated the dynamics of head motion in parents and infants during an age-appropriate, well-validated emotion induction, the Face-to-Face/Still-Face procedure. Participants were 12 ethnically diverse 6-month-old infants and their mother or father. During infant gaze toward the parent, infant angular amplitude and velocity of pitch and yaw decreased from face-to-face (FF) to still-face (SF) episodes and remained lower in the following Reunion (RE). During infant gaze away from the parent, angular velocity of pitch decreased from FF to SF and remained lower in the RE. Windowed cross-correlation suggested strong bidirectional effects with frequent shifts in the direction of influence. The number of significant positive and negative peaks was higher during FF than RE. Gaze toward and away from the parent was modestly predicted by head orientation. Together, these findings suggest that head motion is strongly related to age-appropriate emotion challenge, are consistent with the hypothesis that perturbations of normal responsiveness carry-over even after the parent resumes normal responsiveness in the reunion, and that there are frequent changes in direction of influence in the postural domain.