Bonding between parents and children is often shaped by small, everyday moments – a hug, shared playtime, or a quiet conversation. But scientists are now finding that these repeated interactions may leave a biological trace that builds over months.
In a new study, scientists discovered that mothers with higher long-term levels of the bonding hormone oxytocin, measured in hair samples, tended to share stronger emotional connections with their preschool children.
Researchers at Ben-Gurion University of the Negev (BGU) found that oxytocin levels in mothers and children often moved together, and higher maternal levels were linked to warmer, more responsive interactions.
The findings suggest that the biology of bonding may develop gradually alongside the everyday rhythms of caregiving.
Why saliva tells less
A single saliva test can change dramatically within minutes, and a 2020 analysis found that results often vary from one visit to the next.
The body releases quick bursts of this hormone in response to touch, stress, or attention, so the exact timing of the test can strongly affect the reading.
Researchers often collect saliva right after a task or a moment of interaction, such as a cuddle, but these brief snapshots may miss the patterns that build up over weeks.
Hair samples provide a slower, longer-term signal that reflects hormone levels over time, though scientists are still working to understand exactly what those measurements represent.
Bonding begins in biology
Scientists tie parenting and bonding to oxytocin, a brain-and-body messenger that shapes social attention and caregiving behavior.
Neurons release it during close contact, and it can calm stress responses while making social cues feel more noticeable.
In parents, that chemical nudge supports gentle touch, eye contact, and back-and-forth timing that helps children stay regulated.
Even so, a hormone linked to connection does not guarantee connection, because culture, sleep, and hardship also shape behavior.
Hormones preserved in hair
Scientists have used hair samples for more than a decade to measure cortisol, the hormone linked to the body’s stress response.
As hair grows, small amounts of hormones circulating in the bloodstream become trapped inside the strands, creating a record that builds up over time.
In the lab, researchers cut a short section of hair close to the scalp and measure the average hormone level stored in that segment, which reflects several weeks rather than a single moment.
This method cannot capture day-to-day fluctuations, but it can reveal longer-term patterns that develop gradually, much like relationships shaped by repeated everyday interactions.
Measuring bonding in families
In the 2026 study, researchers collected small hair samples from 28 mothers and their children, who were between 3 and 5 years old.
The team at BGU also observed each pair during free play, rating how warm, responsive, and engaged their interactions appeared.
They then compared those interaction scores with oxytocin levels measured from both the mothers’ and children’s hair, which reflect hormone activity built up over several months.
This approach allowed the researchers to connect biology and behavior, but it could not determine whether hormone levels influenced interaction quality or whether everyday interactions shaped hormone levels over time.
Mothers and children aligned
Across the sample, children showed higher hair oxytocin levels than their mothers, a pattern that surprised the research team.
Within each pair, however, mother and child levels tended to move in the same direction, meaning higher maternal levels often paired with higher child levels.
This alignment hints at shared biology, shared environments, or shared daily routines, even though the data cannot separate those possibilities.
A single hair reading cannot show who influences whom, but it does suggest that the two bodies remain biologically connected.
Maternal oxytocin levels also lined up with better emotional interaction during observed play, especially when children’s levels were low to average.
When a child’s oxytocin levels were already high, the mother’s level mattered less for the warmth and responsiveness researchers recorded.
The pattern suggests that a child’s biology can sometimes buffer or amplify how maternal chemistry shows up in behavior, reinforcing that a simple high–low hormone score can never fully explain a relationship on its own.
Further research is needed
A Hebrew-language article about the project stressed that the findings were early and still needed tougher testing.
With a narrow sample, the study could not test whether the same hair-based bonding patterns hold across different cultures, stresses, or family structures.
“These results highlight the complex role of oxytocin in mothers and children in shared emotional processes between them,” said Professor Florina Uzefovsky, who led the study.
Before anyone treats hair oxytocin as a personal score, researchers need larger samples, shared protocols, and clearer biological meaning.
Hair reveals bonding patterns
Future studies at BGU could test fathers, track families over years, and examine whether parenting programs shift hair oxytocin levels alongside observable behavior.
Because this biological marker changes slowly, it may reveal whether an intervention influences everyday parent–child interaction rather than reflecting only a single good day.
“The study shows a stable body measure for mother and child behavior and their relationship, and it demonstrates oxytocin in hair for understanding the mother-child bond,” said Uzefovsky.
Any real-world application would also raise privacy concerns, since hormone levels can reveal sensitive biological information that individuals may not intend to share.
Still, hair-based hormone measurements could help researchers connect day-to-day caregiving with biological patterns that accumulate quietly over months.
If larger studies confirm the signal, the approach may guide long-term family research while remaining far from any clinical shortcut.
The study is published in the journal European Neuropsychopharmacology.
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