Baby smell
Hexadecanal has no perceptible odour, but that when you sniff it, it affects the way you behave toward others. Image Credit: Shutterstock

Turns out babies are more than just cute and cuddly – they are also quiet manipulators. A new study, published in the journal ‘Science Advances’ last month, found that a chemical secreted by a baby’s scalp incites visceral gendered responses.

The study, conducted by the Azrieli National Center for Brain Imaging and Research at the Weizmann Institute of Science in Israel, only tested 127 participants – 67 men and 60 women – but the findings were surprising. The researchers had expected aggression to spike in both genders, however there was a marked difference in response to smelling the hormone.

The study found that in the case of women, it triggers aggression whereas in men, it tempers it. “We found that HEX [Hexadecanal] has no perceptible odour, but that when you sniff it, it affects the way you behave toward others — specifically, your aggressive responses to others,” Dr Eva Mishor, who led the study, was quoted as saying by New York Post.

She added that this could just be an evolutionary development. “Male aggression translates many times into aggression toward newborns; infanticide is a very real phenomenon in the animal kingdom. Meanwhile, female aggression usually translates into defending offspring,” she said. “HEX, it would seem, affects men in that there was more social regulation, their aggression was kept in check and it served as a ‘cool down’ signal for them, while in women the regulation decreased and it can be thought of as a ‘set free’ signal.”

Paula Surdo, an expat and mum of two, says: “I kind of agree with that finding, because it’s a human instinct for the mum to become more protective. Think of a cat, for example, when she has kittens she gets aggressive. Men on the other hand are not as wound up. So this reaction is probably just animal instinct.”

Mum Chinsea Tedeschi agrees with this assessment, saying that women are also prone to going overboard in their protectiveness so it’s not so inconceivable that aggression is a hormonal reaction to a baby’s smell.

Infants speak to us – but it’s through a silent bond, through hormonal secretions that over generations we’ve learnt to read.

“Babies cannot communicate through language, so chemical communication is very important for them. Functional magnetic resonance imaging scans have revealed that though men and women similarly perceive HEX as having no odour, their neurological response to it are radically different. Women react aggressively whereas men do not,” explains UAE-based Clinical Psychologist Sneha John, who works at Camali Clinic.

UAE-based mum Marissa, who requested to be identified with only her first name, says she loved smelling her kids’ scalps, but it didn’t make difference to her temperament: “Years ago, I really enjoyed smelling my then babies scalp. Now, at age 7 and 10, I enjoy smelling their arms and faces, for example. I love the sweet smell they still have. I couldn’t say if when they were babies the smell incited aggression in the protective sense of the word ... maybe subconsciously?”

Baby and mum
When Hexadecanal is emitted, it triggers a response in the left side of the brain known to process social cues like gestures and expressions.

How does HEX work?

John explains: “When Hexadecanal is emitted, it triggers a response in the left side of the brain known to process social cues like gestures and expressions. The brain then sends the message to a part called the amygdala, which controls aggression in humans.”

Pakistani expat and mum-to-two Naima Alvi Bawany says that while the term ‘aggression’ is a bit confusing in this context, she can understand the need to protect the kids. “I can understand that…peace and contentment that comes with kids. I used to think it was cuddling but it could be this. I’m not sure.

“I remember my father-in-law; he passed away five-six years ago, he would hold my kids and smell them, and he’d say, ‘children are like milk but grandkids are like the cream’. And he would hug and smell and say it revitalised him.”

Perhaps we shouldn’t be surprised at this visceral reaction; studies have shown that humans have instinctive reactions to smells; they trigger memories and emotions and in some cases, recognition. UAE-based mum Sneha Kothari says: “Regardless of what causes intoxicating aroma, scent plays a pretty powerful role and is directly connected to our brains. The body odour of babies develops a mother-infant bond and triggers memories.”

The bond is elemental. Did you know? Mums can identify their newborns just by smelling them. According to a study, published by the US National Library of Medicine National Institutes of Health in 2009, mums could distinguish between their baby’s scent and others even six hours post birth, even though they had been separated from their baby for most of that time. The reverse – a baby’s natural affiliation for the smell of his/her mother - is likewise true.

What can we say … the nose always knows.

Have a story to share? Write to us at