A new study has found correlations between levels of hormones in fathers in the first days of the birth and their caring activity during the following months.
Earlier research has strongly established a link between lower testosterone in fathers and higher investment in the care of infants and children. Similarly, higher levels of cortisol in fathers play a role in focusing their attention on the infant.
Researchers have proposed a “behavioural synchrony” model, whereby parent and infant interact through care, physical touch and gaze to create matching hormonal reactions in each. Whilst popularly attributed only to mother-infant interactions, the same patterns are seen in father-infant interactions. Humans have evolved a strategy in which fathers commonly cooperate with mothers to raise infants, and this is underpinned by hormonal changes in fathers.
The study took place in a hospital in UNICEF designated “baby-friendly” hospital in Indiana, USA, and involved 298 fathers.
Levels of testosterone and cortisol were measured on the day of the birth, both before and after one hour of holding the baby. The levels were measured again at the same time the next day. Then, 2-4 months later, fathers were asked to assess their own level of engagement in direct care (e.g. bathing and dressing), indirect care (e.g. arranging childcare and washing clothes) and playing.
The researchers found that lower testosterone levels on day 2 were correlated with greater participation in direct and indirect care during the following 2 to 4 months.
They did not find such correlations for day 1 and suggest as an explanation that testosterone levels on day 1, just after the birth, are immediate reactions to events of the moment and less related to longer-term orientations. They suggest that their new research is complementary to recent work by other scholars showing correlations between later caring activity and fathers’ testosterone levels through the pregnancy.
Higher cortisol levels immediately after the birth predict greater future involvement in direct and indirect care and in play. Greater increase in cortisol while holding the baby was correlated with later indirect care and play (but not direct care).
The researchers surmise that there are other processes in play that fully explain these findings, which need further study. For example, cortisol reactivity may be influenced by different experiences during the pregnancy. Also, cortisol reactivity may depend on how the baby is at the time, for example, calm or crying, something that was not measured in this study. The study did observe large variations between fathers in cortisol levels and changes.
The study is a new contribution to understanding how hormonal changes in fathers around the birth contribute to parenting behaviour. UNICEF’s baby-friendly standard for hospitals requires support for mother-baby bonding, but not for father-baby bonding, despite this and other evidence that father-baby bonding is friendly to babies.
Kuo PX, Braungart-Rieker, Lefever JEB, Sarma mS, O’Neill M & Gettler LT (2018), Fathers’ cortisol and testosterone in the days around infants’ births predict later paternal involvement, Hormones and Behavior
Photo: © UNICEF/UN0205047/Zehbrauskas