Nature Versus Nurture

by Aleksandra Hurka

Psychology Department, Lake Tahoe Community College

PSY210-01: Introduction to Biological Psychology

Professor Gina Curasi

July 28, 2025

Effect of Heredity on Behavior

Genetics have a contributing effect on a person’s addiction to substances; particularly nicotine and alcohol. GABRA4 and CHRM2 genes are known to be linked to alcohol abuse disorders. In a scientific study the activity of the brain was measured using electroencephalograms (EEGs), it was found that EEG activity peaked on top of two genes (GABRA4 and CHRM2) on chromosomes 4 and 7 (Posthuma et al., 2006). Since measuring EEG activity helps detect neurobiological disorders associated with alcohol overconsumption, this disturbance in EEG activity proves that disorders such as alcoholism are genetically linked. It is also known that CHRM2 gene at 7q has previously been associated with IQ (Posthuma et al., 2006), which could imply its linkage to alcohol dependency is associated with the rise of cognitive dysfunctions.

Effect of Environment on Behavior

The environment around people also has an influence on a person’s choices, such as drinking and smoking. In a study done to evaluate how people chose their friends based on their peers’ substance use, students were sampled from both a large school and small high school. It was found that in the large school, 31.1% of students drank monthly, while only 15% of students drank in the small school, yet drinkers were more popular at the small school with the ratio of increase in peers forming ties with drinking adolescents in the small and large schools were 15% and 4%, respectively (Wang et al., 2016). This could be due to the fact that at small schools, peers have less options of people to make friends with, which explains the differences in ratios. Additionally, contrary to the popularity of drinkers in the small school sample, it was found that smokers were more popular in the large school sample, and evidence was found that engaging in one type of substance could increase chances of using another. (Wang et al., 2016). This suggests that people chose friends who are more similar to them when it comes to drinking and smoking, yet could change their substance use habits based on their peer environment.

Environmental and Hereditary Interactions on Behavior

Research indicates there is a correlation between environment and hereditary influences on specifically personality. In a study done to evaluate personality shifts of adopted versus non-adopted children, the adopted children when first introduced to their new families were seen to be extroverted and highly emotionally stable compared to the biological children, however over time experienced a decline in socialization and emotional stability (Loehlin et al., 1990). This decline in extroversion could be explained by the fact that if a child was in an environment over time for a long period of time and got used to it, the effort to be initially extroverted declined as they got used to the household environment. This could explain how their personality would match those of the biological children who had lived in the household their entire lives. On the contrary, this study also indicated that biological parents of the adopted children were less emotionally stable (Loehlin et al., 1990). This could be evidence of a heredity factor causing a shift to the child’s personality, rather than the environment since the children’s personality is genetically shifting to match their biological parent.

As far as whether heredity or environment has the greater impact on behavior, research shows varying results. In an IQ test done to evaluate whether adoptive children have scores more similar to their biological or adoptive parents, the mean of the scores for the children, biological parents, and adoptive parents were 115, 95, and 115, respectively (Mullen, 2006). While the actual IQ score of the child was more similar to their adoptive parent, the ranked increasing order of the scores from the 9 individuals evaluated was more similar between the child and biological parents. It could be argued that when looking to evaluate IQ score, environment plays a larger role, while if looking to evaluate the rank of the scores, heredity is the greater contributing factor.

Opinions and Conclusions

Before looking into how biological and environmental factors played a role in human behavior, I was thinking that not one serves a greater importance than the other. Through this research, however, I was able to see situations when one had a greater impact as well as times when both were equally as important. I believe that mental illnesses also have a huge influence on behavior and thought processes which is something that's very individualistic. Whether these mental illnesses are hereditary or a result of environmental surroundings and lifestyle would explain people’s personalities, choices, and cognitive abilities. I think for myself, I believed that my environment was a contributing factor to my high academic success in the subject of math. When comparing myself to both of my parents, both of my parents don’t find themselves successful in this field so therefore I believe my academic success in math was an acquired skill rather than something hereditary. On the contrary, I knew a girl who was several years younger than me who without studying in my calculus class got perfect scores and her parents were also both highly skilled mathematicians, which leads me to believe for her, genetics could have played a role in her ability to comprehend highly complicated numerical problems and her thought processes. However, I noticed that I am a bit similar to my parents where whenever I’m talking with other people I’m talking a lot like my mom- very fast and asking a lot of questions. I usually tease my mom that she talks to people as if she were interrogating them, but when I think about my own habits, I may share similar traits with my mom which leads me to think that this is a genetic factor affecting my behavior when communicating with people. However, it could also be that because my mom and I live in the same household environment, I naturally just picked up on the habit of fast paced talking because I heard it so often around me.

References

Loehlin, J. C., Horn, J. H., Willerman, L., Loehlin, J. C., Horn, J. M., & Willerman, L. (1990). Heredity, environment, and personality change: Evidence from the Texas adoption project. Journal of Personality, 58(1), 221-243. https://doi.org/10.1111/j.1467-6494.1990.tb00914.x

Mullen, J. D. (2006). NATURE, nurture, AND INDIVIDUAL CHANGE. Behavior & Philosophy, 34, 1-17.

Posthuma, D., Cherny, S. S., & Boomsma, D. I. (2006). Introduction to the special issue: Human linkage studies for behavioral traits. Behavior Genetics, 36(1), 1-3. https://doi.org/10.1007/s10519-005-9010-2

Wang, C., Hipp, J. R., Butts, C. T., Jose, R., & Lakon, C. M. (2016). Coevolution of adolescent friendship networks and smoking and drinking behaviors with consideration of parental influence. Psychology of Addictive Behaviors, 30(3), 312-324. https://doi.org/10.1037/adb0000163