To what extent do environment and education shape our moral compass, and how responsible is the genetic cocktail we inherit from our parents? Recent research aims to get to the heart of the matter.
The well-known "nature versus nurture" debate goes back hundreds of years, and it is still of interest today.
It asks whether certain behaviors are rooted in our natural inclinations, or whether our social environment shapes them.
Recently, the release of the documentary Three Identical Strangers reignited some discussions into the importance of environmental factors and education versus that of heritable traits.
The documentary presents the case of a contentious "twin study" (or in this case "triplet study") conducted in the 1960s. It involved separating identical triplets during infancy and adopting them out to different families as "only children" to assess how the siblings would evolve throughout their lives.
A new study by Pennsylvania State University in State College, the University of Oregon in Eugene, and Yale University School of Medicine in New Haven, CT, followed sets of siblings in an effort to better understand whether our moral compass is solely down to our upbringing, or whether our genetic inheritance also has a say in the matter.
First study author Amanda Ramos, from Penn State University, refers to a person's moral qualities as their "virtuous character" and explains that both nurture and nature could work together to shape them.
"A lot of studies have shown a link between parenting and these virtuous traits, but they haven't looked at the genetic component," says Ramos.
However, she adds, "I thought that was a missed opportunity because parents also share their genes with their children, and what we think is parents influencing and teaching their children these characteristics may actually be due, at least in part, to genetics."
So, Ramos and team conducted a study investigating the extent to which "virtuous character" is a heritable trait. The researchers report their findings in the journal Behavior Genetics.
The impact of heritable traits
The scientists worked with 720 pairs of siblings with different degrees of relatedness. They ranged from identical twins who grew up together in the same environment to half-siblings and step-siblings with no common genetic material but who grew up under the same roof.
"If identical twins are more similar than fraternal twins, for example, it's assumed there's a genetic influence," says Ramos. She adds, "Including multiple degrees of relatedness can give you more power to disentangle the genetic influences from the shared environment."
The scientists assessed the relevant data — such as parental practices and the children's apparent sense of responsibility — in two rounds: first, during the siblings' adolescent periods, and then again when they were young adults.
Ramos and team found that nurture, in the form of positive parenting — that is, reinforcing and rewarding good behavior — did correlate with a stronger sense of responsibility in the children. However, they point out that this association was notably more visible in siblings who not only grew up in the same environment, but who were also related by blood.
"Essentially," continues Ramos, "we found that both genetics and parenting have an effect on these characteristics."
"The way children act or behave is due, in part, to genetic similarity and parents respond to those child behaviors," she adds, explaining, "Then, those behaviors are having an influence on the children's social responsibility and conscientiousness."
Genes do not fully determine behavior
Co-author Jenae Neiderhiser stresses that these findings do not indicate that nature trumps nurture when it comes to a person's moral compass and conscientiousness — far from it.
Still, she suggests keeping in mind that a person's DNA sets the tone for more than their physical appearance.
"Most people assume," explains Neiderhiser, "that parenting shapes the development of virtuous character in children via entirely environmental pathways. But our results suggest there are also heritable influences."
"This doesn't mean that if parents are conscientious that their children also will be regardless of how the children are parented. It does mean, however, that children inherit a tendency to behave in a particular way and that this shouldn't be ignored," she adds.
However, Ramos also reminds us that having a particular inclination does not mean that a person cannot educate themselves to overcome it or develop it, as the case may be.
At the end of the day, what matters most are the conscious choices a person makes on a daily basis.
"Your genes are not totally deterministic of who you are. Genes simply give you a potential. People still make their own choices and have agency in shaping who they become."