Shhh, The kids can hear you arguing (even when they're asleep)

For years now, psychologists have been telling couples who yell at one another to stop for the sake of the kids. Such conflict in the home — even when no violence is involved — is associated with a host of negative behavioral and life outcomes for children. Some strands of research have gone so far as to suggest that dissolving a marriage might be better for kids than exposing them to high levels of conflict within a bad marriage.

Still, the effects of parental conflict do not appear to be experienced equally by all children. Some kids do badly when exposed to conflict; others seem to cope much better. Recently, researchers at the University of Oregon decided to try to get a handle on this variability: Is it possible, they asked, that experiences early in life might sculpt the brain in ways that shape the child's response to conflict later in life?

Psychologists Alice Graham, Philip Fisher and Jennifer Pfeifer decided to take a look at what happens inside the brains of infants when they hear conflict and angry voices. The approach was straightforward: Use a noninvasive brain-scanning technique known as fMRI to scan the brains of infants and identify, in real time, which areas of the brain are activated by angry voices.

There was one problem. These brain scans required the infants to lie really still for an extended period of time in a noisy scanner. The odds of that happening: close to zero.

That is, unless, the psychologists reasoned, the infants were asleep. Was it possible that even during sleep, the brain continued to take in and process angry voices?

In a study published in Psychological Science that is at least as remarkable for its methodology as for its results, the researchers had a couple of dozen infants brought into a brain-scanning lab at bedtime. First, the parents rocked the infants to sleep. Then Graham and her colleagues carefully placed the sleeping children inside the brain scanner. Via a pair of headphones, they piped in voices saying nonsense sentences such as, "I pulimented a mopar." The voices spoke in different tones — angry, neutral and happy.

Graham, a doctoral student at the school, said the most surprising thing was not that the brains of infants responded differently to the different tones — which suggests that the brain is more than capable of taking in information while a child is asleep — but that there were stark differences among the children. Infants who came from homes with lots of conflict, where the parents yelled at one another and called each other unpleasant names, showed a heightened activation in certain areas of the brain.

"What we see for the infants in higher-conflict homes is that they are showing greater reactivity to the very angry tone of voice," Graham says, "and that reactivity is in brain regions that we think are important later on in terms of your ability to regulate your emotions and function well."

The scientists acknowledged that it's not immediately clear what the findings mean. If the infants from high-conflict homes are especially reactive to angry voices, this could be consistent with the studies that have found that conflict in the homes is psychologically damaging for children. On the other hand, it's also possible that the heightened activation is connected with the way the brain develops resilience: The brain activation might point to the possibility that the infants were learning to deal with high conflict. The only way to find out would be to follow such children over time and see what happens to them. Graham says the study is just a first step toward understanding the role of early influences in how children come to process conflict.

And as for advice to quarreling parents, she says, the bottom line might be simple: Your kids are listening to you, even when they are asleep. Copyright 2019 NPR. To see more, visit https://www.npr.org.