Babies bond better with strangers when they can smell their mother

Maternal body odour signals to babies that they can safely build relationships with other adults, a trait that may have evolved so that mothers can share the load of child rearing

By Alice Klein

Babies are more socially receptive to unfamiliar women when they can smell their mother’s natural body odour, suggesting that maternal scent functions as a safety signal.

Previous research has found that mothers’ unique smell signatures allow their babies to recognise them and have a soothing effect when they are in pain.

Yaara Endevelt-Shapira at The Interdisciplinary Center in Herzliya, Israel, and her colleagues wondered if signals in maternal odour also change the way that infants respond to strangers.

They asked 62 mothers to wear cotton T-shirts for two consecutive nights and avoid using deodorant or other scented products, so that their natural smell would rub off onto the clothing.

Their babies – aged 7 months on average – were then strapped into chairs and introduced to an unfamiliar woman who was about the same age as their mother, lived in the same area and was a mother herself.

When the babies had their mother’s T-shirt under their nose, they were more likely to smile, laugh and gaze at the stranger than if they were sniffing an identical unworn T-shirt.

Electroencephalography (EEG) devices fitted to both participants’ heads showed that the babies’ electrical brainwaves were also more likely to synchronise with the stranger’s when they could smell their mother’s T-shirt. The same kind of brainwave synchronisation is found between babies and their mothers when they gaze at each other and is thought to be a sign of feeling mutual connection.

The findings suggest that “maternal body odours can assist infants in transitioning to social groups, exploring new environments and communicating with unfamiliar partners”, says Endevelt-Shapira.

This could explain why bringing a “transitional object” like a blanket or cuddly toy from home can help young children settle into nursery school, because it might smell a bit like their mother, says Endevelt-Shapira. The researchers didn’t look at whether the scent of fathers or other familiar caregivers can have a similar effect.

Human babies benefit from bonding with adults other than their parents because they are more helpless than the young of other species and often require a wider circle of care, says Endevelt-Shapira. This may be why maternal odour facilitates these external relationships, she says.

The current study found that maternal scent helps babies to bond with women who are similar to their own mothers, but more research is needed to see if the effect extends to women from different cultures and men, says Endevelt-Shapira.

Journal reference: Science Advances, DOI: 10.1126/sciadv.abg6867

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