Stress, Neural Systems,and Genetic Code

An Interview with Neuroscientist Judy Cameron

How do scientists know this?

Child psychologists and other scientists learn about behavior by carefully studying behavior in various situations. For example, conducting a “playroom test” is one way we assess a young child for anxious behavior. A mother and child enter a playroom with lots of interesting toys; the mother is asked to sit nearby and to neither encourage nor discourage play. Most young children will sit on their mother’s lap for a few minutes and then climb down to investigate the toys. A very anxious child is less exploratory, very worried about leaving the mom, or may leave the mother but return to her repeatedly for comfort.

Of course, much of what we know about associations between early experience, interaction and the developing brain has been learned through animal studies. Using monkeys as our experimental subjects, we have conducted essentially the same playroom tests and achieved similar results. Using such tests allows careful examination into how inherited traits, as well as life experiences, alter the behaviors that are displayed under specific conditions. In other studies using monkeys, one-week-old infant monkeys living in a social group had their mothers removed from the group (a stressful early life experience). We found these young monkeys grow up to be much less interested in social interaction compared to monkeys nurtured by a mother or an adoptive mother. They didn’t develop close bonds with other monkeys. Although a normal adult monkey would spend an average of about a quarter of its waking hours in close social interaction, an animal that had experienced maternal separation at one week of age would spend just eight to ten percent of its time in close interaction. In contrast, monkeys experiencing the same early life stress just a few weeks later, at one month of age, grow up to seek increased social interaction with other monkeys, even into adulthood. These monkeys are “clingy” and seek a lot of social attention. Extrapolating from there, think of the implications for a society, a workforce, or a community where children grow up to be less social than normal, or alternatively seeking more social interaction than normal.

Regarding children, then, what can we glean from your work?

Two outcomes have been well documented in children who have experienced early life stresses, especially the early life stress of a broken affiliative bond—such as growing up in orphanages or foster care. Sometimes, these children have an increased desire for socialization, and become profoundly clingy. If they are in school, these children will always want the teacher’s attention. Or, conversely, such children can react to early life stress by becoming somewhat dissociated and not very social. Even if adults try to interact with the child, he or she is detached from adults (and from other children), and not likely to do what adults want them to do, or to seek activities that will please adults. Detachment is much less common than increased clinginess, but it is certainly well documented in humans who have had profound early life stress.

What we are seeing in studies using infant monkeys is a confirmation of those two characteristics we see in children who have experienced the early life stress of a broken affiliative bond: detachment, with a decreased desire to socialize; or an increased desire to socialize. Both outcomes are accompanied by various anxious behaviors. Imagine the effect on a community if a sizeable portion of its members are disaffected. Those communities are likely to be unstable, and we all feel the impact.

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