How do the environments that you subsist in interact with your genes to influence behavior (environments of any kind, from social to ecological, count)? ("Environment and Natural Resources")
(Plomin, DeFries, Knopik, and Neiderhiser)
As described in last week's post, I am revisiting the concepts of genotype-environment correlation and genotype-environment interaction for two weeks as I attempt to qualify/fix the definitions and explanations that I had used in prior posts. Last week, I covered the subject of genotype-environment correlation, and this week, I plan to cover the subject of genotype-environment interaction. This concept relates to and explains the behavioral differences between introverts and extroverts in that it reveals the tendencies of individuals to act based upon their genotypes, depending on their expression in the current situation. The central idea behind the concept of genotype-environment interaction is that individuals are genetically predisposed to certain conditions (say, introversion or extroversion), and upon assimilation into the environment, depending on the situation, these predispositions may tend to come out. Unlike genotype-environment correlation, the point of focus in genotype-environment interaction is not the fact that genotype plays a role in determining one's environment (although this is still significant), but it is instead the individual's reaction to such environment and the tendencies and predispositions that bear fruit without actually manipulating the situation.
("Behavioral Genetics")
To start from the beginning, according to Behavioral Genetics, Sixth Edition, by Plomin, DeFries, Knopik, and Neiderhiser, genotype-environment interaction is defined as "genetic sensitivity or susceptibility to environments." In theory, both cognition (thinking) and genetics (inherent instinct) determine behavioral traits, thereby suggesting that one's behavioral traits, or at least the predispositions to express such traits, are inherited from the individual's parents. These traits, which can also be expressed as genetic sensitivity or susceptibility, play a role in determining one's behavior in certain environments. The focus of genotype-environment interaction is the individual's response(s) to a variety of environments (taking into account both environment type and individual's reaction/response), as affected by genetic predisposition. This concept, in integrating both genetics and environment into explaining one's behavior(s), thereby suggests that behavioral traits, such as social introversion or social extroversion, are products of both nature (biology) and nurture (environment). One of the basic theories of genotype-environment interaction, as articulated in Behavioral Genetics, is that, "when considering the variance of a phenotype, genes can affect the phenotype independent of environmental effects, and environments can affect the phenotype independent of genetic effects. In addition, genes and environments can interact to affect the phenotype beyond the independent prediction of genes and environment."
Adopted, separated identical twins are often used in genotype-environment interaction research studies. ("Genetic research-twin studies, family studies and adoption studies")
For example, research has shown that adopted children whose birth parents had criminal convictions have an increased risk of criminal behavior, thereby suggesting genetic influence (in terms of aggression and obedience). In addition, research has shown that adopted children whose adoptive parents had criminal convictions also have an increased risk of criminal behavior, thereby suggesting environmental influence. However, adopted children have been shown to be at an increased risk of criminal behavior when both their adoptive and biological parents have had criminal convictions in the past, thereby indicating genotype-environment interaction. Not only do genetics affect the individual's behavior, but so does environment. When individuals exhibit a genetic predisposition to a behavior, any corresponding environment amplifies this tendency/behavior. Similar studies have indicated links between genotype-environment interaction and depression or alcoholism. Further studies have been conducted concerning genotype-environment interaction making use of separated, adopted identical twins. Research has revealed that when a pair of identical twins are separated by adoption, the two individuals are subject to exhibit similar yet slightly different behaviors due to their environment, with the individual whose environment encourages this behavior more to exhibit it more often (for example, two twins may be separated at birth by adoption; one goes to a family where the parents have exhibited criminal behavior(s), while the other one goes to a law-abiding family; both can still become criminals, but the one subjected to the environment with criminal adoptive parents is more likely to exhibit criminal behavior; the child living with adoptive parents who have exhibited criminal behavior may grow up to hold up banks and assault pedestrians, whereas the child living with the law-abiding adopted parents may grow to steal candy and gum from gas stations and commit tax fraud). Further research into such subject has also shown that the likelihood of either member of this pair of twins exhibiting the behavior is greater if their biological parents exhibited such behavior, as compared to the likelihood of either member of a separate pair of twins exhibiting the behavior if their biological parents did not exhibit such behavior. The point/findings/result of twin adoption studies are that biology and genetics can create a predisposition to a behavior, which is then fulfilled/amplified if the environment is related to/accommodates the situation for such behavior.
Therefore, in essence, if an individual is dissatisfied with being an introvert or an extrovert, they have both their parents and their environment to blame. Individuals inherit predispositions to behavioral traits, such as being an introvert or an extrovert, from their parents, and depending on their environment, which may encourage or discourage such behavior/identification, the behavior can be amplified. Because individuals have genetic predisposition to behave instinctively, depending on the situation, their behavioral traits are influenced by both nature and nurture. Thus, this concept is termed as "genotype-environment interaction" in that an individual's genotype and environment factor in, or interact, to determine the individual's normal behavior, such as acting as an introvert (speaking little, avoiding eye contact, keeping head down, etc.) or as an extrovert (speaking loudly and quickly, pursuing social contact, keeping head up, etc.), in such situation. However, because genotype and environment affect and influence, but do not determine, behavior, their actions in certain situation are ultimately up to cognitive reasoning and processing (although this can also be affected by nature and nurture). Therefore, the individual truly may only have themselves to blame for when they complain about being introverted and extroverted; nature and nurture are simply biased third parties that influence behavior, whereas cognition is the ultimate factor.
("Gene-Environment Interaction")
As a side note, yet another individual has participated in my survey comparing behavioral differences between introverts and extroverts as well as public opinion of the two groups! Thus, I now have three responses to my survey! If you can find some time to participate in this "overwhelming movement," please feel free to click on the link posted below and take my survey! In all honesty though, I really would appreciate, if you are reading this blog post, that you take a few moments to participate in my survey and then encourage others that you know (family, friends, pets, inanimate objects, etc.) to do so as well. I thank you in advance.
https://www.surveymonkey.com/s/62238YL
Works Cited:
"Behavioral Genetics." Macmillan Education. Macmillan Education, 2013. Web. 13 Feb. 2015.
"Environment and Natural Resources." University of Wisconsin-Extension. University of Wisconsin System, n.d. Web. 13 Feb. 2015.
"Gene-Environment Interaction." National Institute of Environmental Health Sciences. Department of Health and Human Services, n.d. Web. 13 Feb. 2015.
"Genetic research-twin studies, family studies and adoption." ISE IB Psychology 2012. Tangient LLC, n.d. Web. 13 Feb. 2015.
Plomin, Robert, John C. DeFries, Valerie S. Knopik, and Jenae M. Neiderhiser. Behavioral Genetics. 6th ed. New York: Worth Publishers, 2013. Print. Pages 118-127.
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