Direct eye contact from an adult speaker appears to shape which words babies learn by aligning the infant’s brain activity with the adult’s, a effect that may act as a learning switch. A new study, conducted across the United Kingdom and Singapore and published in Nature Communications, suggests that this one-way neural coordination helps link a caregiver’s gaze to an infant’s selective word learning. The research team involved Wei Zhang of Nanyang Technological University and Victoria Leong, a professor at NTU’s School of Social Sciences and the Department of Pediatrics at the University of Cambridge.
Babies grow up amid a cacophony of sights and sounds, and they rely on ostensive cues—signals such as direct gaze or infant-directed speech—to identify information worth learning. The study focuses on interpersonal neural coupling, a measure of how strongly activity in one person’s brain predicts subsequent activity in another’s.
Previous developmental work has shown social cues influence language acquisition. For instance, a 2003 study found nine-month-olds learned unfamiliar foreign speech sounds when interacting with a live person but not from identical video lessons, while a 2017 study reported stronger brainwave synchrony when an adult made direct eye contact with a baby. Yet it remained unclear what such shared brain activity truly accomplishes.
The authors address this gap by testing whether adult-to-infant neural synchrony underpins selective learning in social contexts. Leong said: “We had previously published a seminal demonstration that eye contact modulates adult-infant neural synchrony. The current study replicates (across two countries) and extends these findings to show that neural synchrony underpins infants’ selective learning in social contexts.”
Forty-seven nine-month-old infants participated in the experiment, with 29 from the United Kingdom and 18 from Singapore. The British infants came from English-speaking households, while the Singaporean group came from bilingual English-Chinese families. All infants were developing typically.
In the lab, infants watched a monitor displaying a female speaker reciting three artificial languages. Each language comprised four three-syllable words, such as “pe-tu-do” or “di-lo-ga,” spoken in a steady cadence without emotional inflection. The sequences contained statistical cues that help identify word boundaries, mimicking natural speech patterns.
To isolate the effect of eye contact, the speaker wore polarising glasses and, crucially, the camera could be adjusted to vary eye visibility. In the full gaze condition, the glasses appeared transparent and eyes were fully visible; in the partial gaze condition, the lenses darkened like sunglasses; in the no gaze condition, the lenses were opaque. The experiment kept the speaker’s delivery constant while changing only eye visibility.
Each block began with a familiarisation phase, during which babies watched the speaker for 60 seconds while researchers recorded eye movements and brain activity via electroencephalography. In the testing phase, infants heard either valid words from the languages or artificial nonwords made by crossing syllables between words. The researchers assessed learning by measuring how long babies looked at the screen, with longer looking at nonwords indicating recognition of the language’s structure.
Behaviourally, infants showed selective learning only when the speaker’s gaze was fully visible. On average, they looked 1.22 seconds longer at nonwords than at words in the full gaze condition, a small to moderate effect. In the partial gaze condition the difference was 0.76 seconds, and in the no gaze condition it was 0.34 seconds.
“We’re not passive sponges,” Leong explained in the Cambridge news release. “They heard all three languages, but only learned the one, which was when they could see the speaker’s eyes.” The researchers emphasised that this learning pattern could not be explained by general differences in visual attention, as infants spent similar amounts of time watching the speaker across all gaze conditions.
Co-author Kaili Clackson, from the University of Cambridge, framed the finding as a gap between looking behaviour and learning. “Even when the infants seemed to be staring at a screen attentively, unless there was eye contact, nothing was going in – the information washed over them,” Clackson said. “The brain synchrony shows that it’s a selection process.” She added: “These cues are really powerful because when you preface new information with them, they tell the baby: this is important, you need to listen.”
When comparing the UK and Singapore groups, Singaporean infants watched the speaker longer than their British peers, a pattern the authors attributed to possible differences in response to unfamiliar Western facial features. However, learning performance did not differ significantly between the two groups, and both cohorts reacted similarly to the presence or absence of gaze.
Leong suggested the findings illuminate early cognitive development across cultures. “This suggests that although there are already cultural differences in what we pay attention to or find novel from 9 months of age, the brain’s learning mechanisms set infants up to learn in a fundamentally similar way across cultures.”
To probe the neural basis of the effect, the researchers examined alpha rhythms—brainwaves around 6 to 9 cycles per second—in 42 usable brain recordings. They investigated whether the adult speaker’s brain activity could predict later infant brain activity as they watched.
The analysis found that adult-to-infant coupling predicted learning beyond chance, explaining about 25 percent of the variation in learning, versus around 20 percent for models built on shuffled data. In contrast, the infants’ own internal brain connectivity did not predict learning, though it correlated with a parent-reported checklist of early communicative gestures, explaining about 34 percent of the variation (versus roughly 22 percent for shuffled data).
The team also assessed neural entrainment, the tendency of brainwaves to track the rising and falling loudness of speech. Full gaze strengthened this tracking at a few recording sites but, on its own, entrainment did not predict learning. A mediation analysis suggested that adult-to-infant coupling may bridge eye contact to learning: stronger coupling was observed with full gaze than with no gaze, and stronger coupling aligned with greater learning. The authors described this as preliminary, noting the coupling metric was chosen for its predictive value for learning.
“Eye contact helps the baby decide what is important to learn in a social context, acting as a ‘switch’ to synchronize their brainwaves with those of the speaker and facilitating learning,” Leong said.
The findings echo earlier PsyPost coverage of eye contact promoting aligned brain activity, though the prior work examined spontaneous synchrony between familiar adult pairs rather than adult-to-infant coupling during learning.
Beyond theoretical implications, the researchers highlighted practical takeaways for caregivers. “As parents, we need to be conscious of the need to use social cues like eye contact and calling your child’s name, as these cues don’t just focus your child’s attention, they activate the learning process,” Leong said. “If you’re on your phone and distracted when you’re trying to give them instructions or teach them something, there’s less of a likelihood that they’ll take it seriously or learn compared to if you put your phone down and look them in the eye.”
The study is modest in size, with 47 infants for behavioural testing and 42 for brain recordings. The authors acknowledge that subtler effects in the partial gaze condition might emerge more clearly in larger samples, and that the study used pre-recorded video rather than live interaction. They also note that infants succeeded in learning statistical word patterns from video, unlike previous live-interaction findings from 2003.
Other caveats include the possibility that eye contact plays a different role in communities where physical closeness is emphasised, as seen in some Arab cultures. Methodologically, the researchers limited their analysis to a single shared frequency band (6 to 9 Hertz) for practical reasons, even though typical adult alpha waves peak higher. Finally, while the statistical models reveal associations, experimental manipulations would be needed to establish a direct causal link between neural coupling and learning gains.
The study, “Adult-to-infant unidirectional neural coupling mediates selective social learning in infants from the United Kingdom and Singapore,” lists Wei Zhang, Kaili Clackson, Stanimira Georgieva, Lorena Santamaria, Vanessa Reindl, Valdas Noreika, Nicholas Darby, Vaka Valsdóttir, Priyadharshini Santhanakrishnan and Victoria Leong as authors.
