The brains of bilingual mothers and their young children remain closely synchronised during play, even when interacting in a second language, according to a new UK study published in Frontiers in Cognition.
Interbrain synchrony refers to the simultaneous activity of neural networks across the brains of people who are socially interacting, such as when talking, learning, singing, or working together. This alignment is thought to strengthen emotional connection, improve communication, and focus attention. It is also considered important for healthy bonding between parents and children.
Researchers found that this neural alignment is not disrupted when bilingual mothers use an acquired language with their child.
“Here we show that the brains of bilingual moms and their kids stay just as ‘in sync’ through neural synchrony irrespective of whether they play in the mom’s native language or in an acquired second language,” said first author Efstratia Papoutselou, a research fellow at the School of Medicine at the University of Nottingham.
“This is an important finding because it suggests that using a second language doesn’t disrupt the brain-to-brain connection that supports bonding and communication.”
Many children worldwide grow up in multilingual families. In the EU, the percentage of mixed-language households rose from 8% to 15.6% between 2014 and 2023. While the social, cognitive, and academic benefits of bilingualism are well documented, the researchers explored whether speaking more than one language could affect parent-child bonding.
Even highly proficient speakers may speak a second language more slowly and with more pauses or corrections, particularly in emotionally charged or demanding situations.
“Second-language speakers often report a sense of emotional distancing when using their non-native language, which may influence how they express affection, discipline, or empathy in parent-child interactions,” wrote the authors.
The team studied 15 UK families with children aged three to four who had been raised bilingually. English was not the mothers’ first language, but all had achieved C1 or C2 proficiency under the Common European Framework of Reference for Languages.
During a laboratory visit, each mother and child sat at a table with toys while wearing caps fitted with functional near-infrared spectroscopy technology (fNIRS). This method measures changes in oxygen levels in blood vessels in the brain as an indicator of neural activity.
Pairs took part in three randomised conditions: playing together in the mother’s native language, playing together exclusively in English, or playing independently and silently with a screen separating them.
The measurements showed statistically significant neural synchrony in each mother-child pair. Synchrony was stronger during interactive play than during independent play.
The strongest synchrony appeared in the prefrontal cortex, which is involved in decision making, planning, reasoning, and emotion. Weaker synchrony was observed in the temporo-parietal junction, a region linked to social cognition and attention.
Crucially, synchrony was equally strong whether the pairs played in English or in the mother’s native language.
The researchers concluded that using an acquired language did not affect a mother’s ability to synchronise brain activity with her child during interactive play. The findings suggest that the neural foundations of bonding and learning remain intact across languages when proficiency is high.
“Bilingualism is sometimes seen as a challenge but can give real advantages in life. Our research shows that growing up with more than one language can also support healthy communication and learning,” said senior author Douglas Hartley, a professor at the NIHR Nottingham Biomedical Research Centre.
The study used a naturalistic free-play approach with hyperscanning, a technique that records brain activity from two people simultaneously. The results confirm that interbrain coupling in bilingual mother-child pairs remains stable across languages when language proficiency is high, underscoring the resilience of neural mechanisms that support parent-child bonds.