The Science Behind the ‘Nature vs. Nurture’ Debate

It’s really nature AND nurture that impact human development. Read on to learn more.

For many years, scientists and philosophers have debated the relative merits of viewing our development into mature, adult beings as the result of either nature (i.e., the innate characteristics we inherit from our parents’ genes) or nurture (i.e., all the experiences we have as we live) (Gelman, 2000).

Nature

In this debate, nature is defined as more than just our parents’ genes (Gelman, 2000). We can add to this category any knowledge that seems baked into each species such that it does not need to be learned. For example, many species instinctively stop near the edge of the physical plane that they are on – they recognize without having to learn the hard way that if they kept going, they would fall down that cliff or steep hillside and hurt themselves. The capacity for language also seems to be innate to humans – all of us, as long as we grow up exposed to one, are born capable of learning most any language.

Nurture

On the other side of the nature vs. nurture debate are scientists who argue that most of what matters in our lives are things that we learn as we grow. Since much of our learning occurs under the care of older humans, this is the nurture side of the debate. On this side of the debate, scientists are concerned with arguing that there is very little that is innate to our existence and that most anything of importance is learned (Gelman, 2000).

There are almost no examples in the development of humans, or any species, of personality traits or behaviors that are solely the result of nature or nurture (Stiles, 2011). It is almost always a case of nature and nurture interacting to shape who we are. In any given moment, you are the sum total of your genes, all of your experiences, and all the changes that have happened in your lifetime (Stiles, 2011).

Scientists have a word for the phenomenon of our genes and environments interacting to shape who we are: epigenetics (Haque et al., 2009). To understand why it is almost always nature and nurture, not nature versus nurture, we will look at many examples of epigenetics in action in this article.

“The problem, of course, with the idea of nature versus nurture was that it posed a choice between determinisms.”
― James S.A

Nature vs Nurture in Twins

Since identical twins each have the same genetic makeup, they have been involved in the forefront of studies regarding the nature vs. nurture debate (Plomin et al., 2003). By studying these sets, in particular those that have been raised in different environments, scientists can attempt to isolate the effects of nature and nurture (Bouchard et al., 1990). In other words, these twin studies can help us see what the impact of our genes is, separate from our environment and epigenetic changes (those changes that result from the interaction of genes and environment).

These studies have shown that genes do strongly influence who we become (Bouchard et al., 1990), although the degree of influence varies from trait to trait. Knowing this, scientists can then look at the differences in genes across these twins to try to determine which genes, or groups of genes, most strongly influence these outcomes. And if there is great variation in how certain diseases happen across these twins, we can reasonably guess that the environments they live in are more influential than their genes in shaping that disease risk (Boomsma et al., 2002).

At the same time, these twin studies also offer a window into which aspects of our environments influence our development the most. For example, researchers might study the parenting behaviors of identical twins who were raised apart. They study this in order to determine how (and how much) specific parenting behaviors influence our development.

How Does Nature vs Nurture Affect Human Development?

Twin studies offer a window into how much nature, nurture, and their interaction determine aspects of human development. For example, it would appear that on average, a person’s weight is determined mostly by their genes, as is their likelihood of being hyperactive; the environment is less influential in determining these outcomes (Plomin et al., 2003). At the same time, twin studies show that our environments strongly impact our cognitive development, perhaps just as much as our genes (Plomin et al., 2003).

In Sum

The fact that our genes change over time, according to the experiences we have, means that we get to change ourselves. None of our traits and tendencies, whether good or bad, pleasant or unpleasant, are permanent. Insofar as we are ready, willing, and able to change our environments and choose different experiences, we can mold ourselves over time into different people – ideally, the versions of ourselves we have always wanted to see. We never stop changing and very little about us is fixed in place, so we can take action to determine what those changes look like.

References

● Boomsma, D., Busjahn, A., & Peltonen, L. (2002). Classical twin studies and beyond. Nature Reviews Genetics, 3, 872–882.

● Bouchard, T. J., Lykken, D. T., McGue, M., Segal, N. L., & Tellegen, A. (1990). Sources of human psychological differences: The Minnesota Study of Twins Reared Apart. Science, 250, 223–228.

● Gelman, R. (2000). Domain specificity and variability in cognitive development. Child Development, 71(4), 854-856.

● Haque, F. N., Gottesman, I. I., & Wong, A. H. (2009, May). Not really identical: epigenetic differences in monozygotic twins and implications for twin studies in psychiatry. In American Journal of Medical Genetics Part C: Seminars in Medical Genetics (Vol. 151, No. 2, pp. 136-141). Hoboken: Wiley.

● Plomin, R. E., DeFries, J. C., Craig, I. W., & McGuffin, P. E. (Eds.) (2003). Behavioral genetics in the postgenomic era. American Psychological Association.

● Stiles, J. (2011). Brain development and the nature versus nurture debate. Progress in Brain Research, 189, 3-22