Fathers can be primary attachment figures
Some evidence suggests that when fathers do take on the role of being the main caregiver they adopt behaviours more typical of mothers.
FIELD (1978) filmed 4 month old babies and found that primary caregiver fathers, like mothers, spent more time smiling, imitating and holding babies than secondary caregiver fathers.
These behaviours are related to interactional synchrony and the formation of an emotional attachment (ISABELLA ET AL 1989).