Field for fathers being important?

Filmed 4 month old babies in face-to-face interation with primary caregiver mothers, secondary caregiver fathers and primary caregiver fathers. Primary caregiver fathers, like mothers, spent more time holding and smiliing and imitating with babies more than secondary fathers. Important for reciprocity and interactional synchrony, part of the attachment formation, potential to be more the emotional focused primary attachment figure - prodive responsivness requried for a close emotional attachment but perhaps only as the primary caregiver.