Oxytocin, dubbed 'the hormone of love and bonding', is elicited during sexual intercourse, and is involved in maintaining close relationships.
Now, Ruth Feldman, psychology professor at Bar-Ilan University in Israel and colleagues have measured plasma oxytocin from sixty-two pregnant women during their first trimester, third trimester, and the first postpartum month.
They also observed the mother and child interact, defining the level of attachment along four aspects: gaze, affect, touch, and vocalization. Stronger attachment would mean that the mother focused her gaze mostly on the child, exhibited a positive energy towards the child, maintained constant affectionate and stimulating touch with the child, used a "motherese" speech with the child, and these species-typical maternal behaviours were adapted to the infant's alert state.
After the mothers completed an extensive survey and an interview on their bond-related thoughts, feelings, and behaviours, the researchers computed the link between levels of oxytocin and bonding.
The results are fascinating. Initial levels of oxytocin at the first trimester predicted bonding behaviour. Therefore, mothers with a high level of the hormone at the beginning of the pregnancy engaged in more of the aforementioned bonding behaviours after birth.
Additionally, mothers who had higher levels of oxytocin across the pregnancy and the postpartum month also reported more behaviour that supports the formation of an exclusive relationship (i.e. singing a special song to the infant, or bathing and feeding them in a special way). These mothers were also more preoccupied by thoughts of checking on the infant, the infant's safety when they are not around, and the infant's future.
This study suggests that women with higher levels of oxytocin during their first trimester are primed to the formation of an exclusive bond with their infants. The findings also show that oxytocin is related to the mental, as well as the behavioural, aspect of bonding. More generally, this study confirms that there is a cross-species continuity in mechanisms that motivate species-specific expressions of bonding.
The study appears in the November issue of Psychological Science, a journal of the Association for Psychological Science.