In recent years, social and cultural changes to human society have resulted in a shift in the parental involvement in childrearing. Traditionally, women have played a larger role in the upbringing of infants. Involvement from the father has substantially increased in the last few decades but there is still considerable variation as to paternal involvement across different cultures.

For some time it has been assumed by many that women are “hardwired” to be mothers. Some suggested that while pregnancy and labor trigger caregiving in women through certain neurobiological processes, the father’s brain may adapt to parenting through an involvement in childrearing. Until now, however, no such studies had investigated this theory.

In order to investigate any changes that may occur in the father’s brain with childrearing experience, a team of researchers led by Ruth Feldman from Bar-Ilan University gathered study participants from two different first-time parenting duos in Israel. One group of parents consisted of biological mothers and fathers where the mother was the primary caregiver, although the fathers also played significant roles in childrearing. The second group consisted of homosexual male couples where one of the males was the biological father of the child. The homosexual couples assumed responsibility of the children very shortly after birth and played equal roles in childrearing.

The study involved making video recordings of the parents interacting with the children at their homes, and also the parents and children alone. Shortly before and after each recording was made saliva samples were also collected in order to measure levels of a hormone called oxytocin. Oxytocin has many nicknames, such as the “trust hormone” and the “love molecule”. This hormone also acts as a neurotransmitter and is released during various activities such as sex, birth and breast feeding and plays a significant role in bonding.

A week later, the parents were played back the recordings of themselves interacting with their children and then given a functional MRI scan to look at brain activity. The researchers found that all of the participants displayed activation of 2 distinct but linked regions that together were coined the “parenting network.” One of the systems was the emotional processing network which contains structures such as the amygdala and is involved in reward and motivation, amongst other things. The other system was the mentalizing network that contains regions such as the superior temporal sulcus and is implicated in social understanding and empathy.

The researchers also unveiled some differences between the parents. In general, they found that the mothers displayed greater activation in the emotional processing networks, whereas the heterosexual fathers displayed greater activation in the socio-cognitive circuits that are more experience-dependent. In both cases the increased activation was correlated with oxytocin levels and behavior. According to the researchers, these results seem to suggest that while the mothers may be naturally more geared toward nurturing and protecting, which could be due to the surge of certain hormones during pregnancy and childbirth, the fathers may have to develop these qualities through experience of childrearing.

What is perhaps more intriguing is the finding that the brains of the homosexual fathers were different to that of the heterosexual fathers. They exhibited activation of the amygdala which was comparable to that of the mothers, but also activation of the superior temporal sulcus (STS) which was similar to that of heterosexual fathers. In all of the men, the connectivity between the amygdala and the STS was linked to the amount of time spent looking after the infants.

Taken together, these results strongly suggest that caregiving experience can tune the parenting networks of the fathers in a similar manner to that of mothers which likely results from processes during pregnancy and childbirth.