Summary: Researchers discovered that eye contact acts as an intentional switch that synchronizes brainwaves between infants and adult speakers, directly driving language acquisition.
The cross-cultural study monitored 8 to 10 month old infants using electroencephalography (EEG) as they listened to novel nonsense languages. The team revealed that infants only learned a novel language when they had clear, unobstructed visual access to the speaker’s eyes.
Inter-brain neural synchrony between the baby and the speaker predicted language learning success more reliably than the infant’s independent brain activity alone, proving that social signals actively gate cognitive processing in the infant brain.
Key Facts
- Neural Synchronization Mechanism: Making direct eye contact triggers inter-brain neural synchrony between an adult speaker and an infant, creating a dedicated cognitive pathway for processing incoming linguistic information.
- Visual Gating Experiment: Researchers exposed 42 infants (aged 8 to 10 months) in Cambridge and Singapore to nonsense languages paired with speakers wearing clear glasses, partially shaded glasses, or fully dark opaque glasses.
- Selective Learning Outcomes: Infants maintained equal visual orientation time toward screens across all conditions, but successfully learned vocabulary only when the speaker’s eyes were completely visible.
- Inter-Brain Synchrony Over Individual Activity: Inter-brain neural alignment between the speaker and the infant was a significantly stronger predictor of language retention than the infant’s isolated brainwave activity.
- Cross-Cultural Universality: The findings were consistent across both UK and Singapore cohorts, proving that visual social gating is a fundamental, non-culture-specific mechanism in human neurodevelopment.
Source: University of Cambridge
Infants use eye contact with speakers to work out what to pay attention to and synchronise their brainwaves, helping them learn language, scientists in Cambridge and Singapore have shown.
Infants are surrounded by a vast range of stimuli that compete for their attention – sights, sounds, voices – and must somehow work out which things are worth paying attention to and learning from. To do this, they often rely on social cues – eye contact, ‘baby speak’ or someone calling their name, for example – but how this helps with learning is not clear.
Professor Victoria Leong and colleagues at the University of Cambridge, UK, and Nanyang Technological University (NTU), Singapore, have previously shown that when an infant and adult make eye contact, their brainwaves synchronise with each other.
Now, in a study published in Nature Communications, they have shown that eye contact helps the baby decide what is important, acting as a ‘switch’ to synchronise their brainwaves with those of the speaker and help them learn.
To do this, the team got infants in both countries to listen to three nonsense languages formed from triplets of syllables repeated over and over again. Each of these languages was paired with a speaker who appeared on a screen wearing glasses – in one setup, her glasses were clear; in a second, her glasses were partially shaded, making it more difficult to see her eyes; in the third, her glasses were dark, making it impossible to see her eyes. The same speaker was used for all three languages.
During the first part of experiment, when the infants were being familiarised with the languages, the team examined the infants’ brainwaves using electroencephalography (EEG), which measures patterns of brain electrical activity via electrodes in a skull cap worn by the participants. 42 infants aged eight to 10 months from the UK and Singapore took part in this test. The researchers had also recorded the brainwave patterns of the speaker at the time of recording the videos while they spoke the languages.
To test whether the infants had learned the language, the speaker then presented them with individual phrases from the different languages as well as new made-up words. Infants would be expected to spend more time looking at speakers who are using an unfamiliar language than one they were familiar with.
Professor Leong, from the School of Social Sciences at NTU and the Department of Paediatrics at the University of Cambridge, said: “We let the infants listen to all three languages and it turned out they were selective in what they learned. They’re not just passive sponges. They heard all three languages, but only learned the one, which was when they could see the speaker’s eyes.”
The researchers found that when a baby was learning the language, their brainwaves were more likely to be in sync with those of the speaker. In fact, the level of synchrony was more important for predicting learning even than the brain activity of the infants themselves. But crucially, brain activity was only synchronised when the baby could fully see the speaker’s eyes.
The infants tended to look at the screen for the same amount of time, regardless of whether they could see the speaker’s eyes, but eye contact was crucial for helping the baby determine which language was important.
Dr Kaili Clackson from the Department of Psychology at the University of Cambridge said: “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. The brain synchrony shows that it’s a selection process.”
The researchers found this phenomenon to be true in both Cambridge and Singapore, suggesting it is universal, not culture specific. However, in Singapore, infants spent more time in general looking at the speaker – possibly because the speaker’s ethnicity was less familiar to them and hence more novel – though this did not affect learning.
Eye contact is one of the social signals that communicate intention to the listener. However, there are other social cues that do this, too, such as smiling, pointing and using the infant’s name. These may be particularly important in cultures where eye contact between a child and adult is less important – or even frowned upon, as it is in some Arabic countries.
Dr Clackson 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.”
The researchers say they hope the findings will make parents more aware of the need to engage actively with their children.
“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,” said Professor Leong.
“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. This is an important way of signalling your intentionality, your seriousness, that you want them to pay attention and learn something.”
Funding: The research was supported by A*STAR and the Ministry of Education, Singapore.
Key Questions Answered:
A: Infants live in an environment overflowing with competing sensory inputs. Inter-brain synchrony acts as a biological filter or selection switch that aligns the neural firing patterns of the learner with the instructor. This phase alignment signals to the infant’s brain that incoming acoustic data is intentional, highly relevant, and worth encoding into long-term memory.
A: No. The infants looked at the video screens for identical lengths of time regardless of whether the speaker wore clear, shaded, or dark glasses. However, without direct eye contact, visual attention did not translate into cognitive processing or language acquisition, demonstrating that passive looking is insufficient for early learning.
A: The study highlights that passive exposure to language, such as background audio or distracted caregivers looking at mobile devices, fails to trigger the inter-brain synchrony needed for optimal learning. Direct engagement, such as eye contact, calling a child by name, and face-to-face interactions, actively signals intentionality and engages the biological mechanisms required for cognitive development.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this neurodevelopment and language research news
Author: Craig Brierley
Source: University of Cambridge
Contact: Craig Brierley – University of Cambridge
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Unidirectional adult-to-infant neural coupling mediates infants’ selection of socially-relevant stimuli for learning across cultures” by Wei Zhang (张维), Kaili Clackson, Stanimira Georgieva, Lorena Santamaria, Vanessa Reindl, Valdas Noreika, Nicholas Darby, Vaka Valsdóttir, Priyadharshini Santhanakrishnan & Victoria Leong. Nature Communications
DOI:10.1038/s41467-026-75831-x
Abstract
Unidirectional adult-to-infant neural coupling mediates infants’ selection of socially-relevant stimuli for learning across cultures
Infants possess powerful learning abilities, but their neural resources must be deployed parsimoniously toward the most relevant information in a given social context.
Adults curate infants’ information selection through ostensive marking of valuable content using social cues such as eye-contact. However, the neural mechanisms that support social gating of early learning remain unclear.
Here, we demonstrate that – in infants from UK and Singapore – unidirectional adult-speaker to infant-listener neural coupling mediates infants’ selection of socially-relevant information for learning. Specifically, speaker-to-listener neural coupling is modulated by the adult speaker’s eye contact and predicts selective learning of an artificial language that is paired with full (compared to partial or no) eye contact.
Speaker-to-listener neural coupling is a better predictor of selective learning than infants’ own neural activity, suggesting that this signal effectively captures important social influences on early cognition, and may provide insights into social valuation decision-processes that dictate early social learning.
