We found that the increase in oxytocin happened via a different pathway in fathers, involving actual parenting and not pregnancy and childbirth.
Oxytocin has been considered for nearly a century as a “maternal” hormone due to its involvement in labor, contractions and in the creation of breastmilk. Over the last two decades, human oxytocin research has shown this hormone’s involvement in all aspects of human sociality, including empathy, social collaboration, theory-of-mind, and romantic love. Oxytocin’s involvement in fatherhood, however, has remained less understood than its role in motherhood.
Over the past few years, studies from our lab have begun to unravel the role of oxytocin in the development of fatherhood and in patterns of paternal care. We measured oxytocin in fathers from three angles. First, we measured levels of the hormone in plasma, saliva, and urine in relation to paternal behavior. Second, we administered intranasal oxytocin to fathers and examined its effect on the father’s and the infant’s physiology and behavior. Finally, we imaged the brain response of mothers, fathers, and primary-caregiving fathers to their infant’s cue to assess the “parental brain” and its links with fathers’ oxytocin.
The first set of studies surprisingly revealed that fathers have similar levels of baseline oxytocin as mothers, and in both mothers and involved fathers oxytocin levels are higher compared to individuals who did not recently have a baby. This was found even in the first weeks following childbirth and even when mothers were breastfeeding. This was the first indication that fathers are biologically prepared to care for infants, as mothers are. We found that the increase in oxytocin following childbirth happened via a different pathway in fathers, involving actual parenting and not pregnancy and childbirth.
We found, however, that oxytocin was linked to a different set of parenting behaviors in fathers. Mothers’ oxytocin was linked to maternal affectionate touch, talking in “motherese” and mutual gazing, while fathers’ oxytocin correlated with a “paternal” way of interaction – highly arousing play, focus on joint exploration, and stimulatory touch. We further found that after 15 minutes of affectionate touch in mothers and stimulatory contact in fathers, both parent and infant’s oxytocin increased significantly, highlighting the role of parent-specific relational behavior and tactile contact in activating the production of oxytocin.
The second set of studies administered an oxytocin nasal spray to fathers and examined the effect of this on the father’s and the infant’s hormones, heart rhythms, and relational behavior. We found that this increased the father’s oxytocin, decreased the stress hormone cortisol, altered testosterone production and augmented the expression of paternal behavior. Moreover, we found that when fathers were under the influence of oxytocin, the infant’s oxytocin levels were also significantly higher compared to placebo and they increased their social orientation and social behavior. These surprising findings show how parent and child can influence each other’s oxytocin levels and the role of the hormone in developing the child’s social repertoire.
In our studies of parents’ brains, we found that oxytocin was linked to the brain changes we observed in both mothers and fathers. Following up with children from mother-father and two-father families we found that their social and emotional competencies were similar. We found a link between their development and earlier changes in their parents’ brains, all linked to higher levels of oxytocin in both parents and child.