Getting in sync: Mother’s brain may mimic baby’s during play

Research using two-person neuroscience suggests mother-infant brains actually synchronize as they interact

By Nadiyah Dhoraji. Mentored and edited by Elliot Richman.

Children are our world’s explorers, inventors, and adventurers. They spend years discovering the world through play. While solo play is well known to foster social independence, recent studies have been looking into the cognitive effects of joint play. The results of several such studies were presented on February 18 during the American Association for the Advancement of Science annual meeting.

Conforming mum’s brain waves to baby’s

Victoria Leong, affiliated lecturer at Cambridge University and associate professor at Nanyang Technological University, Singapore, was part of a team investigating the neural responses of both mother and child during play. In their experiments, mother-infant pairs were made to play alone in the same room and then together. When playing alone, mother and baby were both given the same toy and had a divider set between them so the parent could see the baby but not the toy the baby was playing with.

The researchers used a technique called dyadic electroencephalography (EEG), which measures the brain signals of two socially interacting people. Their results found that when playing together the baby showed slightly increased attention towards the parent. More surprisingly, though, attention towards the toy also increased. Overall, inattention dropped when the babies played with their mothers compared to when they played alone.

Upon studying the neural underpinnings of this response, the researchers found that bursts in maternal theta power were associated with the babies’ attention. Theta power is a type of activity classified at 4-8Hz and is associated with states of alertness and attention. “It was quite a striking finding — that when they were interacting with their babies the mum’s brain activity changed in various ways so that it began to look more like how a child’s brain behaves during attention phases,” says Sam Wass, professor at the University of East London and leader of the study. But, he adds, “we need to replicate this finding in several studies and investigate it more.”

Looking each other in the eye

In a subsequent set of studies, Leong headed a team that looked at ostensive signals. Ostensive signals, like eye-contact or infant-directed speech, indicate that a person wants to communicate with you. The researchers wanted to investigate whether gaze acted as a cue for neural synchronization in adult-infant pairs. Neural synchronization means a pair's behaviors are coordinated. It affects how we bond, communicate, and learn.

“Previous research has shown that during social interaction we mimic each other’s behaviors — their facial expressions and gestures. We also know that we anticipate each other’s behaviors — we start to prepare a response even as we are listening to what the other person is saying,” Wass explains. “Based on this it’s pretty unsurprising that we’ve started to look at the brains of people when they are interacting,” he adds.

In the experiment described by Leong, the infants were sung a nursery rhyme by an experimenter who gazed at them directly and then indirectly. Results showed that direct gaze produced higher neural synchronization than indirect. “When you’re synchronized with your parent, your states of excitability or receptivity are in sync with your parent, or more simply, the baby is ready to listen when the adult is ready to speak,” she explained at the meeting. This synchrony may help us to communicate better.

Moving towards translational research

Studying these social interactions could one day help to identify disorders of social interaction in patients. “We can use, for instance, non-invasive motion tracking to measure the reciprocity of social interaction and see whether it is within the normal range for a given age group,” says Leonhard Schilbach, psychiatrist and professor at the Ludwig Maximilian University of Munich and not involved in these studies.

Though social observation scales like the Early Social Communication Scales do exist to diagnose different disorders, they rely on the observer's subjective judgment. With the interaction-based sociometric approach, eye tracking movements and posture measurements would be obtained as well. “Hopefully, observer-independent, quantitative measurements will be more accurate and reliable,” adds Schilbach, who is a member of the Munich Center for Neurosciences — Brain & Mind at his university.

While this approach shows promise, larger scale studies need to be carried out with interacting adult-infant pairs across different age groups and gender to determine what kind of interaction behavior is normal. “In psychiatry, we need to use these methods across all diagnostic groups to investigate whether we observe general or disorder-specific social interaction problems,” concludes Schilbach. Only then, he pointed out, could this information help in diagnosis and predicting the best treatment.

Through play, then, it seems we get a glimpse of the world through a child’s eyes, and maybe for a moment we even get to be on the same wavelength as them.

Nadiyah Dhoraji is a neuroscience student based at the University of Manchester in the U.K. She enjoys writing about all things health. Find her on Twitter @nadiyahdh.

Mar. 10, 2022