Some babies are mellow, others are high-strung. And some babies seem prone to anger. Do these early behavioral differences tell us which kids will become defiant and aggressive?
It might seem obvious that an angry baby will become an angry, aggressive child. But when it comes to aggression, your baby’s moods may be less important than the way his autonomic nervous system responds to stimulation and stress. In an interesting new study, the babies who were the least responsive were the most likely to develop aggressive behavior problems as toddlers. Whether the babies were perceived as hot-tempered had nothing to do with it.
To understand, picture this: A 10-month old baby is strapped into a car seat with an unfamiliar adult nearby. His mother is watching him from another room, but he doesn’t know it. All he knows is that a strange, mechanical robot toy is approaching him from about 5 feet away. The robot makes noise and moves its arms, and doesn’t stop its approach until it’s just 6 inches away.
It’s designed to be scary, and it was. When Erika Baker and her colleagues at Cardiff University performed this test on 100 babies, they were careful to allow mothers to enter the room if, during the experiment, the babies seemed too distressed. Twelve of the mothers did that, and 44 of the babies cried at some point during the weird encounter.
But the reactions of special interest were autonomic. How did the experience affect the babies’ autonomic nervous system, the system that regulates mostly involuntary body functions like heart rate, digestion, and perspiration?
In general, our autonomic nervous system kicks into high gear when we encounter something exciting, good or bad: The heart beats faster, the breath quickens, our pupils dilate, and we break out into a sweat. But the level of arousal varies from person to person. Some people, “high arousal” people, are highly stimulated by relatively small things. Others – the “low arousal” people – are far less sensitive. An experience that triggers physiological changes in the average person might barely register for someone with low arousal.
So Baker’s team monitored the babies’ arousal levels by measuring “skin conductance activity,” i.e., changes in perspiration. Each baby had small electrodes taped to his feet, permitting the researchers to track perspiration before, during, and after the robot experience. In addition, the researchers questioned mothers about their babies’ behavior at home, and they asked mothers about their own behavior and feelings.
Two years later, the researchers were able to track down 70 of the families who had participated in the first phase of the study. Now they asked the parents to evaluate their children’s behavior using the Child Behavior Checklist, a standard developmental questionnaire.
The data were in. What were the results?
Baby temperament – as reported by mothers – was linked how much fear a baby showed during the robot encounter. But it wasn’t correlated with autonomic nervous system arousal. And it wasn’t correlated with the development of aggressive behavior problems. A mother’s perceptions of baby anger did not predict antisocial aggression at age 3.
The only measure that did predict future behavior problems was skin conductance reactivity – sweaty baby feet before and during the scary robot encounter. The babies who perspired less had a moderately increased risk of becoming aggressive toddlers.
As always, we have to be cautious about interpreting the results. For instance, it’s always hard to establish the absence of an effect (“mother’s perceptions of infant temperament not predictive”) with a small sample. And what about the people who declined to participate? Though you might argue the robot was no more distressing than many of the strangers that babies meet in real life, I don’t think I’d volunteer for a study like this. If highly sensitive or “high arousal” parents were more likely to opt out, that might have influenced the results.
Still, it’s hard to guess how such parents might have changed the outcome. And while this study doesn’t prove that parent ratings of baby temperament are unrelated to the development of aggression, it suggests that the effect – if it exists – is small. Moreover, the main positive finding of this study is consistent with other research:
In previous studies of children and adults, low autonomic arousal – as measured by skin conductance reactivity – has been linked with aggressive behavior problems.
Why might that be? There are theory popular theories.
In one account, people with low arousal find it harder to pay attention to ordinary things, which gets them into trouble. Another theory suggests that people with low arousal are more fearless, and, therefore, less constrained by the prospect of punishment or other negative consequences of aggression. A third is the well-known “thrill-seeking” or “sensation seeking” explanation. It supposes that low arousal motivates people to engage in a kind of self-therapy, boosting arousal levels by seeking out extra stimulation – some of which may involve aggression.
The theories aren’t mutually exclusive, and in fact they all offer hope for concerned parents. They suggest we can help low arousal children avoid aggressive behavior problems by applying some common sense. Does your kid have attention problems? Help him develop stronger self-regulation skills. Is he unfazed by punishment? Try focusing on the rewards of good behavior and the development of empathic, moral reasoning. Is he motivated to seek out thrills? Give him lots of positive opportunities to excite his senses and experience awe.
It’s not a recipe for perfection. Some kids present really difficult challenges. But understanding low arousal may help us focus on what these kids need the most.
