New Delhi: Leaving a worn t-shirt or blanket carrying a mother’s scent beside a baby is one of the oldest parenting tricks in the book. Babies are already stamped with their mother’s scent long before birth, having absorbed it while floating in amniotic fluid in the womb, and that familiarity helps them settle and nap a little longer.
Fathers don’t get that biological head start through pregnancy and birth. But a new study in Science Advances suggests infants can still recognise and respond to dad’s body odour, even when he isn’t in the room.
Smell is one of the earliest senses to mature in mammalian newborns, developing well before hearing and vision. Researchers have long known that chemical signals from the mother shape babies’ social and cognitive development, helping them respond to familiar versus new faces and calming their brain and body when something feels frightening. But researchers are only beginning to explore whether infants recognise and respond to their father’s scent in the same way.
“Fathers are becoming increasingly involved in childcare, but we still know much less about their unique contribution to early development,” said Yaara Shapira, lead author of the study.
Smell as a stand-in for the parent
To find out, Shapira and colleagues studied 40 father-infant pairs. Fathers wore a t-shirt for two consecutive nights, which was then stored in a sealed jar. Each infant took part in three brief interactions: one with their own father, and two with an unfamiliar man — one where the father’s t-shirt was present, and one with a fresh, unworn shirt as a control. Throughout all three interactions, EEG caps recorded brain activity from both infant and adult simultaneously, allowing the researchers to measure how synchronised their brain rhythms were.
“We measured whether the patterns of neural activity in the infant and adult become temporally coordinated during interaction. It is a bit like two dancers moving together to the same rhythm,” said Shapira.
During face-to-face interaction, babies’ brains synchronised more strongly with their own fathers than with unfamiliar men. The effect concentrated in a specific circuit: the father’s left central brain region and the infant’s right temporal region, an area tied to social processing.
They also looked at whether infants’ brains synchronised with strangers’. They found that when the father’s t-shirt carrying his body odour was present during a stranger interaction, infant-stranger brain synchrony rose to nearly the same level as in a real father-infant interaction. But when an unworn t-shirt was present instead, the stranger’s and infant’s brain activity showed weaker coordination.
With dad’s scent present, infants smiled and cooed more with the stranger and seemed more excited overall, consistent with the idea that fathers tend to bring exploratory play, while mothers’ presence is associated with calmness and safety.
The researchers also wanted to understand if this effect depended on how involved a father was in caregiving. They asked fathers to fill in a questionnaire to assess their role in day-to-day caregiving. The team found that babies of more hands-on dads showed stronger synchrony in the presence of their father’s scent, suggesting the effect scales with how much sensory exposure a child gets from their father in daily life.
What it means
The authors argue that smell functions as a stand-in for the parent. It might be a sensory bridge that lets an infant’s social brain borrow dad’s presence to feel safe enough to engage with an unfamiliar adult. They suggest that smell can recreate some of the same neural conditions that occur during a real interaction with the parent.
“The importance of body odours in bonding, and cognitive and social development in babies, but also in adult relationships, has yet to receive the attention it deserves. In babies, in the absence of verbal communication, it may play an even larger role,” said Eva Mishor, research associate at Tel Aviv University, Israel, who was not associated with the study.
What’s still unknown
Their findings also suggest that father-infant brain synchrony operates on a different neural mechanism than mother-infant synchrony. Earlier work shows that mother-infant synchrony is carried by the theta rhythm, a brain wave pattern tied to emotional processing. In this study, father-infant synchrony instead rode on the alpha rhythm, which matures later in development and is linked to attention regulation.
Mishor cautions that the study speaks to the role a male caregiver plays in a child’s development, not to fatherhood’s biological role more broadly.
“It’s still not understanding fatherhood’s biological role,” she said. “It sheds light on the different roles parents may have on their child’s development and bonding.”
Shapira is also careful to flag what the study can’t yet answer and what comes next in establishing how a father’s or any other caregiver’s scent shapes infant development.
“An important next step will be to compare paternal body odour directly with the body odour of other family members or an unfamiliar adult. This would allow us to determine whether the observed effect is truly specific to the infant’s own father or instead reflects a more general response to familiar or unfamiliar human body odour,” she said.
(Edited by Prashant Dixit)