A developmental psychologist explains the latest findings into the nature vs. nurture debate, highlighting the need to break down the false dichotomy between genes and the environment.

Question: What are some of the latest insights into the nature vs. nurture debate?

Laurence Steinberg: So the -- what has taken place in the last decade or so has been a complete transformation of the way that scientists think about nature and nurture. And this distinction between what is genetic and what is environmental is now seen as a false dichotomy. It's a bad way to think about things because genes are not directions that our bodies follow, but switches that can be turned on and off by things in the environment. And so just because you have inherited a genetic inclination toward something, toward a certain personality trait, let's say, or toward, you know, being relatively smart -- things that we know have some genetic component to them -- whether that will actually be realized in your behavior is going to be a function of the environment.

And so we can't think of these things separately, and the questions that people were asking decades ago -- which was how much of this is due to nature and how much of this is due to nurture? -- are no longer being asked because we realize now that they're dumb questions. That's not the way things work. They work together, and we need to understand how they interact with each other. So there are studies, for example, showing that there's a genetic propensity to become depressed. Some people have a genetic profile that is going to make them more susceptible to the changes in neurotransmission that effect the onset of depression. But this genetic propensity only turns into depression if people grow up under stressful life circumstances. So if you look at individuals who've grown up under less stressful circumstances, even the ones with the genetic vulnerability don't develop depression. And this is the new kind of science that's being done now that's so exciting in understanding which environmental conditions turn on and turn off which genes. And that's going to be the new frontier in understanding development.

So when parents ask, you know, why did my kid turn out to be different than me, I mean there's so many reasons, because even if your child inherited your genes, unless your child grew up in the exact same kind of environment that you did, they might not be manifested in the same kind of behavior. And you know, parents don't treat all their kids the same way. Siblings growing up in the same family may have very different experiences both within the home and outside the home. I mean, experience matters. So when we read that things have a genetic basis, we need to be cautious in understanding what that really means. Genes don't determine our behavior. They establish propensities, but those propensities are realized differentially in different kinds of environments.