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Genetic Versus Environmental Influences on Personality

Kim has her BA in psychology, with a double minor in sociology and child development. She also has an associate in media communications.

Like Mother, Like Daughter

This image reminds me of my childhood. I know I poked some fun at my mom in this paper but I will always treasure the time I spent with her as a child and even now as an adult.

This image reminds me of my childhood. I know I poked some fun at my mom in this paper but I will always treasure the time I spent with her as a child and even now as an adult.

Are Our Personality Traits Inherited?

We’ve all done this as adults: when asked why we have certain personality traits or bad habits, we firmly state it is because of our parents or due to our upbringing. Now maybe we are joking at times, but in doing this, we all raise a good question: Are our personality traits inherited? The answer to this question is not just a simple yes or no.

Through both nature (your genetics) and nurture (your environment), you can inherit several personality traits at any given time. Take for example my family; I am the youngest child of two. My older brother is almost six years older than I am to the very day. Whenever I describe the clashing differences between my brother and me, I always jokingly blame it on the fact that we’re both strong-headed Aries. I also tell people that every time he’s leaving a certain stage in his life, I’m entering the one he just left, so it makes for a constant sense of disconnect in our relationship. Now, both of these factors may be true, but I firmly feel like it is just something else because, in all reality, the truth is we are two completely different people! Why is this? I always say he is more like our father while I am more like our mother. But how did this happen? Is it because I was forced to go shopping for hours with our mom while he played baseball with our dad, or is it a matter of genetics? Can it be both? Is it more than that?

When my mother talks about me and my brother’s relationship, she tells me how we have never been close and that our differences have existed since I was pretty much born. I find this interesting because certain scientists believe we are born with our personality traits embedded already in our genes. If this is true, my brother and I were never meant to get along! In an article titled “Were you born this way,” the author George Howe Colt “discusses whether genes determine a person's personality” (Colt 1998). Colt gives credit to the effects of both genetic and environmental influences on one’s personality traits. In addition, Colt states “scientists agree that genes establish a base for an individual's personality, but that humans do have the ability to change their personality and inherited traits somewhat by working to develop new habits” (Colt 1998). If Colt’s article was correct, then how could two siblings raised in the same house, brought up by the same parents, become two completely different people? Was it still because we started off as different individuals and thereby could never be molded into having the same personality traits? Or was it a matter of how our personalities developed?

Perhaps a study done on “twenty pairs of monozygotic and 20 pairs of same-sex dizygotic twins, ranging from the ages of 19 to 70, from the Afrikaans and English-speaking populations of the Western Cape” can help us to further explore the inheritability of personality traits in individuals such as my brother and I (Brooks 1998). This study discusses and researches the enneagram personality system, which is the theory that there are “9 distinct personality types” associated with our development and identity (one of which is always dominant.) The study specifically explains to us how siblings raised in the same household can be so different. The enneagram personality system states that “everyone emerges from childhood with one of the nine types dominating their personality, with inborn temperament and other pre-natal factors being the main determinants of our type;” but it also tells us that a child’s “identity, although fluid, is established by the age of four or five years old.” In the study, it was found that by using the enneagram system to study inherited personality traits, a possible explanation could be found for “why children in the same family can be so different in personality” (Brooks 1998). What I found to be interesting about this study was that it also stated there is more than one factor that determines a person’s personality. In fact, it is this multitude of factors that make it such a problem for psychologists and researchers to study inherited personality traits: “Human behavior is influenced by a complex mixture of genetic and environmental factors” (Brooks 1998). It’s sort of like when you try to figure out why one person in the family has a drug addiction when the others don’t; there isn’t just one simple answer.

Another possible answer or theory to this question of the inheritability of personality may have been found in the textbook, An Introduction to Theories of Personality 8th Edition. In this book, the theories and topic of birth order according to Alfred Adler and other researchers are discussed. Alder states that the first-born child may develop lifetime resentment over the loss of attention from the parents to the next arriving sibling (Hergenhahn, Olson 2011 p.112). Ever since I can remember, I was told that my brother was extremely jealous of me when I was a baby, and, unfortunately, as Adler pointed out, his anger only grew when he saw how much I was spoiled. It was as if our potential, common bonding environment (i.e. our home) was the reason for our differing personality traits. Our differences in personality are as opposing as the yin and yang. One researcher that agreed with Adler’s view on personality and birth order theory stated that “Even though siblings share genes and are raised in the same family environment, their personalities can be very different” (Sanders 1997). For example, in my case, my older brother is the rational and reliable one. He prefers to think things through before acting upon them. If given the choice, my brother would choose a safe career over one that would make him happy and would have risks involved. On the other hand, I have always been the more carefree child. I never think before acting, and most of the time I pay for it in spades. He went to college right after high school, got married, got his master’s, and then had children. I went to high school, took some college courses, moved out of my parents’ house, got a job, got broke, made a butt load of mistakes, finally figured out what I wanted to do for a living, and along the way got a few tattoos.

Birth Order and Only Child Influences on Personality

Were our differences in personality simply because he’s older and I’m younger? Perhaps there is some validity and influence behind the enneagram system after all; whereas my brother’s personality may have been formed before I was even born! I definitely think his being older has a lot to do with our personality differences. Because our first memories differ so greatly, the impact of our birth order is much greater. He had 6 years to develop a personality in one environment, but then, after I was born, was forced to adapt to a new environment. On the other hand, I’ve always known just one environment. My sense of security and my development around it is much different than his, despite the fact that we both were raised the same exact way.

When comparing our birth order and personality traits to our cousin Melissa, who is an only child, it is very easy to see the personality differences, while still acknowledging the influence of genetic and environmental factors. As an only child, Melissa is very independent and tends to connect better with adults that are older than her. I can remember when we were growing up how she would always prefer to hang out with her mom and grandmother than the rest of us kids. I do agree with Adler that, like my cousin Melissa, most only children are “very sweet and affectionate” (Hergenhahn, Olson 2011 p.113). In fact, I think some only children can have the tendency to be too affectionate due to their overabundance of affection at home. Melissa spent most of her time with both of her parents until they divorced. Her sweet and affectionate behavior was now torn between a strong independent mother and a lost addiction-stricken father. Her personality soon developed as it needed to in order to adapt to the change in her childhood environment, but her dominant personality traits did not waiver. Actually, the opposite happened, she seemed to become even more loving. For example, recently Melissa got her first puppy. Now, most people are very excited about their first puppy, but Melissa’s excitement is in abundance, giving away the effect and impact certain events had on her personality. Every time she smiles or does something quirky, I may see her father, but I also see everything else too.

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In conclusion, one can see although there is no definitive answer to whether or not personality traits are inherited. However, there is proof that there are a lot of different determining factors that make up our personalities, including genetics. Some are biological, some are systematical, and others are environmental. Take my brother and me for example we both grew up in the same house, were disciplined the same, had the same opportunities, same parents, but still have nothing in common except for all of what I just said. I think because he was born with a different personality than me, our differences were already formed and our experiences in life only solidified that. If he had been forced to walk for hours upon hours through all the isles of T.J. Maxx while I spent the afternoons shooting hoops with my dad, who knows who either of us would be? The ironic thing is my brother and I would still be different and our personalities, inherited or not, would still clash. I guess I could take the easy route out and blame it on my parents, but for now, I’ll just blame it on psychology.


Brooks, D. (1998). “Are personality traits inherited?” South African Journal of Science; Jan98, Vol. 94 Issue 1, p9, 2p, 2 Charts. Retrieved on January 29, 2013 from

Colt, G. (1998). “Were you born this way?” LIFE, New York: 21. 4 (Apr 1998): 38-50. Retrieved on January 29, 2013 from

Hergenhahn, B. & Olson, M. (2011). An introduction to theories of personality (8th ed). Upper Saddle River, NJ: Pearson Prentice-Hall.

Sanders, L. (1997). “Sibling Syndrome.” Business Week. New York: Jan 13, 1997, p.22. Retrieved on January 29, 2013 from

The Enneagram Institute. (1998-2013). “How the enneagram system works.” Retrieved on January 29, 2013 from

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.


Kate on April 05, 2020:

I am the last born. I have three older siblings who were 18 years old, 16 years old and 14 years old when I was born. I’m very close with my siblings and love spending time with them. A brief background story is that my mom was a widow by the time she was 25 years old and had three young children to raise...fortunately my mom had seven siblings to help her out. By the time my mom was 30 years old she married my dad who was 32 years old. When I was born my mom was 40 years old and my dad was 42 years old. Early on when my mom was pregnant with me she thought that she was experiencing menopause until she was pleasantly surprised when her doctor told her that she was pregnant. On a side note, my dad is the first born and has two younger brothers. My dad’s biological parents died when he was a child. My dad and his brothers were raised by one of their aunts. However, I do not know much about my dad’s side of the family. However, my mom was raised by her biological parents and has a fraternal twin brother. My mom has a brother who is 8 year older than her (he was born before World War II). My mom and her twin brother are Baby Boomers who were born in the year 1947. After my mom and her twin brother were born my grandmother gave birth to five more children.

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