It’s an oft-repeated supposition that you can tell whether someone fancies you by their body language: if they mirror how you’re standing or moving, the theory goes, they might just like you back. But romantic partners don’t just have behavioural synchrony — in some cases, they have brain-to-brain synchrony too.
A pattern that has also been observed in musicians and their audiences, brain-to-brain synchrony is a mirroring of neural activity between individuals or groups. And according to a new study in Scientific Reports, such synchrony in spouses could affect how they respond to their children.
Atiqah Azhari from Nanyang University and colleagues first asked 24 Singaporean husband-and-wife pairs how many children they had, and the age of their youngest child. All pairs had at least one child under the age of four. Both parents also provided a “parenting response ratio”, which measured how often either the mother or father took the lead (0:5, 1:4, 2:3, 3:2, 4:1 and 5:0).
The couples were then split into two conditions: half stayed in the same room, whilst the others were separated in different rooms. In both conditions, participants were played a variety of different sounds such as static noise and adult vocalisations, as well as negative and positive sounds of infants crying and laughing respectively. After hearing the sounds, participants rated how distressing they were on a scale of 1 to 5. The team also repeated the same process with control pairs of participants, who had no prior relationship.
Throughout the experiment, parents wore a cap measuring blood flow in the prefrontal cortex of the brain using a technique called near-infrared spectroscopy (a higher concentration of oxygenated blood is related to greater activation in that particular area). To measure synchrony between partners, the researchers looked at how similar their patterns of blood flow were over time.
As anticipated, couples who were sat together showed greater brain synchrony than those who were separated; this synchrony was located specifically in the inferior frontal gyrus, left middle frontal gyrus and bilateral anterior prefrontal gyrus. This was only the case for real partners: the control pairs didn’t show any greater synchrony when together than when apart, suggesting that the presence of an intimate partner, rather than simply any other person, was key to enhancing synchrony.
The kind of sound mattered too: perhaps surprisingly, the sound of infants crying did not increase synchrony between partners who were physically together, while infant laughter, adult laughter and the static sound did.
Given that the brain areas that showed increased synchrony are involved in attention and cognitive control, these patterns could relate to changes in attention and how people parent. This could be beneficial in positive situations, helping parents respond to their children together.
But if there’s a higher level of synchrony when a child is crying, then parents may “catch” or be affected by their partner’s stress, leading to less effective caregiving behaviour. This could also explain why there was no increase in synchrony in the “together” condition during the negative sounds.
This goes some way to explain why younger couples and couples with only one child had higher levels of synchrony compared to older couples. Older couples or those with multiple children were more experienced with parenting, and so their lower synchrony may “reflect a diminished need to respond similarly to each other as they experience greater security in their own roles as parents”, the authors write.
There were several limitations, however. Firstly, parents were played recordings of unknown children and adults: responses to their own child crying or laughing, therefore, may have been very different indeed. The study was also a one-off: looking at synchrony and its relationship to co-parenting over the course of several months or even years may give a better insight into how this mirroring works.