The 3 differences between a shared environment and a non-shared environment

Since it was founded, Psychology has been a science that has tried to explain human behavior.

Since its foundation, Psychology has been the science that has tried to find explanations for why people behave in such different ways.

After decades of investigations and heated discussions about whether genetics or environment have a greater influence in shaping a person's personality and behavior, the already more than famous debate of 'nature vs nurture' has been overcome, giving both factors more or less the same role.

In our genes are some of the causes that make us look more like our parents than the neighbor but, in turn, the neighborhood in which we live or the region where one lives also influence our behavior.

Once the debate was over, they tried to understand something that happens in all families. Although siblings look quite alike, there is always something that sets them apart. Their genotype, even if it is not exactly the same, cannot be. Neither should the environment, because all family members receive the same influences from it, right?

In this article we are going to address an aspect that on many occasions has not been taken into account when it comes to understanding how the environment influences each one of us with respect to our relatives. Let's see how the shared environment differs from the non-shared one.

• Related article: "Differential Psychology: history, objectives and methods

Differences Between a Shared Environment and a Non-Shared Environment: A Summary

Although tragic, the study of behavior, intelligence and personality in identical twins separated shortly after birth has been one of the most beneficial situations to understand to what extent certain phenotypic traits are heritable and which depend on the environment in which one lives. breeding. The premise is that if two monozygotic twins, that is, two genetically speaking clones, live in different houses, those aspects that share will be due to their genetics, while those in which they differ will be due to the environment and/or their interaction with the genotype of these people.

Thomas Bouchard is an American psychologist and geneticist who has studied pairs of twins separated at birth.. In his project, the Minnesota Study of Twins Reared Apart investigated how genetics and environment influence the personality of twins reared apart. In this type of study, genetics is given considerable importance, but it can be observed that the environment influences how people behave.

The environment is understood as the set of aspects external to the person that may or may not exert some kind of influence on personality, cognitive ability and behavior of the individual. Studies of Bouchard's style assume that growing up in different homes implies different environments, while growing up in the same one tends to mean growing up in the same environment.

However, for some time now and even raised in Bouchard's own study, the possibility has been raised that living in a same home and, therefore, growing up with the rest of the biological siblings, does not have to mean that they receive the same influences environmental. The reason for this is the obvious fact that siblings are not equal in behavior and abilities.

It is true that the brothers of the same family have not inherited the same genes each and every one of them, otherwise we would not speak of siblings to dry, but of identical twin brothers. However, the genetic base is there, and that should mean that there were very few differences between siblings, which is rarely the case.

Even between monozygotic twin brothers raised in the same home there are differences. The differences must necessarily be explained by the environment but, having grown up in the same home, how is it possible that behavioral differences still occur?

It is here when we talk about the shared environment and the non-shared environment, two factors within the concept of environment or environmental influences that allow us to understand the differences and similarities of the members of the same family. We are going to address in more depth what these two concepts mean.

shared environment

On many occasions, it has been taken for granted that living in the same family, home, or neighborhood implies receiving the same environmental influences.

Actually, this definition corresponds to what is understood as a shared environment, also called family, that is, those aspects from the environment that appear in the same way to all members of the same family and, therefore, make them more similar among them.

To understand it more clearly, an example of a shared environment would be the home where the siblings live. By living in the same house they all receive the same influence from it.

Another aspect that is considered a shared environment would be living in a bilingual region and, therefore, the siblings could speak two languages ​​with the same fluency since the environment demands it. By mastering all two languages ​​they would have the same type of cognitive stimulation from the environment in which they grew up.

As a third example, I would be the socioeconomic level of the family. If it happens to live in a wealthy family, none of the family members will suffer any kind of situation where there is some kind of nutritional deprivation because of not being able to buy food.

Given that all family members remain in the same environment, which is why it is shared, it is not possible to explain with this type of environment why there are differences between siblings.

• You may be interested in: "Genetics and behavior: do genes decide how we act?"

non-shared environment

The non-shared environment, also called the individual environment, is understood more in terms of influences than the environment itself. It would be the set of factors external to the person that are interpreted differently depending on each member of the same family.

Going back to the case of monozygotic and therefore genetically identical twins, the non-shared environment would be one that would explain why two twins with these characteristics, raised in the same place, can behave differently.

There are several environmental aspects that can exert influences on siblings in different ways. For example, a twin brother may have suffered from more flus throughout his life, or been in a car accident.

Also, as a non-shared environmental factor, there is the different treatment by parents that can be given. It is not uncommon for pairs of twins in which one of the two calls himself the older of the two and who, because of that little detail, behaves more maturely or believes that they should have more rights over the other, and the family environment behaves promoting this.

Another very important aspect, always taking the case of monozygotic twins as an example, is education. Although at home they receive the same discipline, at school it is common for them not to go to the same class and, therefore, have different classmates and teachers.

Family events can be experienced differently between siblings. For example, the death of a relative, something that is sad in itself, can be experienced much more sadly by one of the siblings compared to the rest and affect more deeply.

Beyond biology and genes

Both shared and non-shared environments, as well as genetics, are behind how people are. Although, it should be noted that the research indicates that the influence of the two types of environments is different depending on the evolutionary stage. During childhood, the shared or family environment plays a fundamental role, being something that strongly shapes the person. With the passage of time, the influence of the family environment subsides, and the non-shared or individual environment becomes more important.

In fact, as proof of this, a very general view among adults when asked about what they believe has the most influence on the person's way of being is that genetic inheritance, together with one's own experiences (in many cases leaving how one was raised) are factors to take into account that explain the behavior of each one.

Obviously, this does not mean that extremely harmful childhood situations, such as situations of abandonment and abuse, do not influence how a person may end up being an adult. However, leaving aside the extreme cases, heritability is usually given greater importance along with what individual stimuli have been received throughout life.

Bibliographic references:

• Bouchard, T. J., Jr., et al. (1990), “Sources of human psychological differences: the Minnesota Study of Twins Reared Apart”. Science, vol. 250, no. 4978, p. 223-228.
• Plomin, R. and Daniels, D. (2011), “Why are children in the same family so different from one another?”. International Journal of Epidemiology, vol. 40, no. 3, p. 563-582.
• Plomin, R., et al. (2001), “Why are children in the same family so different? Nonshared environment a decade later”. Canadian Journal of Psychiatry. Canadian Revue de Psychiatrie, vol. 46, no. 3, p. 225-233.
• Plomin, R. (2011), “Commentary: Why are children in the same family so different? Non-shared environment three decades later”. International Journal of Epidemiology, vol. 40, no. 3, p. 582-592.