Some people say it’s mostly about genes. Others argue for the power of the environment. But the reality is complex. Research shows that genes and environmental factors aren’t just “added together” to make a person. Instead, they interact. For instance, experiments on rodents suggest that differences in upbringing can switch certain genes “on” or “off.”
And that’s just the beginning. People caught up in the “genes versus environment” debate often think of individuals as passive. Whether it’s about DNA or early life stress, the story has the same flavor: Individuals are molded by forces beyond their control.
What makes kids turn out the way they do?
In fact, for a long time now biologists and social scientists have been arguing for the active role that individuals play in shaping their own development.
If you’re the parent of more than one child, you’ve probably seen the evidence for yourself. Happy, active babies tend to elicit more friendly attention from strangers. Nervous, inhibited children may get less social stimulation. Kids who are restless and defiant may tend to push their caregivers in the direction of authoritarian discipline. Kids who love to read gain access to better educational opportunities.
We could go on with more examples, but you get the point. Kids aren’t passive lumps of clay. Their behavior influences the kind of feedback they get. And to the degree that children are given any freedom, they make choices that can influence they way they turn out.
On first reflection, this might sound like the triumph of DNA. After all, what makes for these initial differences between babies? Isn’t the whole process kicked off by the child’s genetic potential?
But while genes influence a baby’s temperament, the environment – including the prenatal environment – does as well. And what about monozygotic twins? Babies with virtually identical DNA? When they are raised in the same home, it would seem there is very little to make them different. And yet they, too, make individualistic choices and have their own, unique personalities.
Do these choices lead to measurable differences in the brain? That seems very likely. A new study on mice suggests that our choices can give rise to differences in brain growth – even when individuals live in the same environment and share the same DNA.
As reported this month in the journal, Science, Julia Freund and her colleagues took 40 genetically identical mouse pups and raised them together in one big, stimulating enclosure. Each mouse was fitted with a special micro-chip that allowed researchers to track how much the animal explored its environment.
As it happened, mice showed individual differences in how much they explored, and these differences became ever greater over time. And the more territory mice covered, the more new neurons they grew in the hippocampus, a region of the brain linked with spatial learning and memory.
So despite living in the same environment and starting with virtually identical DNA, these mice ended up with notable differences in behavior and brain.
Where does this leave us? I don’t think it leaves us off the hook. Not when it comes to nurturing children, providing them with opportunities, and giving them a nudge. Even within the context of this mouse experiment, it was clear that the environment makes a difference. When researchers ran a control condition with a far less stimulating home environment, mice experienced less neural growth.
How many kids would end up with strong math skills if we let their childhood preferences determine their educational careers? Spontaneous interest is wonderful, but there are places it won’t take us. Coaxing children to learn mathematics may enrich their lives in ways they can’t imagine when they are very young. The same goes for all sorts of things – learning to read, learning to make friends, learning to cope with impulses and strong emotions.
Still, it’s helpful to remember that kids aren’t passive lumps of clay. In a very real sense, children make themselves. We are just one part of their developmental world.
