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Heredity, the Environment, and Development Essay

The field of behavioral genetics strives to understand how and why we develop the way we do. Behavioral genetics seeks to find how not only heredity, but also environment, plays a role in the development of human beings. The field has evolved quite a bit in the last few years. Studying genetics helps us to be able to predict future behaviors and also potentially help us to use genetic engineering. Since the study of behavioral genetics can potentially lead us down the road of genetic engineering it attracts a lot of controversy.

As will be examined here genetics shows some strong correlations between heredity and environment. The field has studied numerous examples to help explain what is caused by heredity, what is caused by environment, and how the two can be linked together to further understand why we behave the way that we do.

Behavior Genetics”Human behavioral genetics, a relatively new field, seeks to understand both the genetic and environmental contributions to individual variations in human behavior.” (McInerney, 2008) Human behavior genetics studies how an individual’s genetics and environment influences their behavior. “Behavior genetics focus is on the effect of heredity on differences between individuals.” (Boyd & Bee, 2006) Heredity refers to genetic and traits being transmitted from one generation to the next or from the parent to the offspring. “Traits or behaviors are believed to be influenced by genes when those of related people, such as children and their parents, are more similar than those of unrelated people.” (Boyd & Bee, 2006)

Behavior geneticists study behavior genetics and the way they can affect an individual. Behavior geneticists have shown in their studies that heredity can affect some traits and behaviors, like intelligence, shyness, and aggressiveness. The basic concepts of behavior genetics are: phenotypes which are observable or measurable characteristics (hair and eye color); genotype which are genetic complement of an individual, like having a recessive gene for color blindness; polygenic which is many genes influencing a trait but no one gene has a major effect (hundreds of genes influence IQ and personality).

Correlations between Heredity and EnvironmentCorrelation between heredity and environment can be looked at through genotypes or a person’s “unique genetic blueprint” (Boyd & Bee, 2006) and the environment which a child tends to experience. Active genotype environment correlation, evocative genotype environment correlation, and passive genotype environment correlation are three casual mechanisms to describe the correlation between heredity and environment in relationship to human behavior (Scarr & McCartney, 1983, p.4). Genotype environment correlations affect phenotypes through the course of a person’s development (p.4). A child’s development stems directly from traits his or her parents pass along and environmental experiences therefore behavioral genetics has developed theories of the correlation between heredity and environment.

Active genotype environment correlation is defined as a child’s tendency actively to seek environments he or she finds to be “compatible and stimulating” (Santrock, 2002, ¶2). An example would be a child who is introverted tends to seek solitary environments. A child who is extroverted tends to seek out social environments. Evocative genotype environment correlation is “when the child’s genotype elicits certain types of physical and social environments” (¶19). The responses a child receives from his or her environment molds the child’s development. A child who demonstrates a pleasant disposition evokes positive reactions in his or her social environment for example. (Scarr & McCartney, 1983, p.4)

Passive genotype environment correlation describes correlation based on the “rearing environment” (Santrock, 2002, ¶31) supplied by the “biological parents” . The explanation the passive type of correlation is the parent passed the genes to the child and supplies the environment in which the child is raised. The environment a parent supplies is directly related to the parents genes which were passed to the child hence the correlation (Scarr & McCartney, 1983, p.4). The example given by Scarr and McCartney is one of a positive nature. A parent who is well versed and enjoys the activity of reading books reads often to the child. The child will most likely be well versed at reading books and enjoy the activity based on the environment provided and the genotype inherited.

The Ugly Side of EugenicsAs mentioned previously, the ethical study of genetics is a concern. Galton and his American colleague, Charles Davenport, studied and promoted eugenics in an effort to improve the quality of humans and to create a better future for mankind. Galton and Davenport researched patterns for undesirable character traits such as alcoholism, insanity, the propensity for criminality. In time, certain behavioral tendencies were linked to particular races. Lehrman cited examples of Davenport’s characterizations of “Italians as drawn toward crimes of personal violence, Greeks as slovenly, and Swedes as tidy” (1998, ¶8).

Society began to adopt laws and policies based on the principles of Galton’s and Davenport’s findings with the purpose of correcting social and economic problems before they started. Although Nazi Germany was the first country to rationalize mass sterilization and then extermination of a race based on their perceived inferiority, the United States also contributed to the mindset of an inferior people. As many as 30 states had legislation concerning the sterilization of people regarded as genetically inferior. The horror and immorality of the holocaust discredited eugenics. Ethics are a guiding force for today’s human behavior geneticists who seek to understand traits that enhance the human race and those that are harmful (Lehrman, 1998).

Twin StudiesIdentifying traits that are beneficial and those that are harmful is just the first of many steps. Behavior geneticists must also identify correlations between the genes humans inherit and the environment that humans are fostered in. Researchers have an exceedingly difficult task before them since experiences and environments are intricately influenced by genetic predispositions. For example, identical twins both are born taller than average. When they complete surveys for behavioral geneticists, they both score high for people who are extroverted and self-confident.

Is this because they have a “self-esteem” gene, or is this a result of society reacting towards them in a manner with more respect and attention because they are tall (Piercy, nd.)?Likewise, a child who is predisposed towards shyness will not seek out social situations that are uncomfortable to her. She may not choose to participate in organized sports. Whatever athletic ability or talent she may possess will remain dormant. Due to her choices, she will not receive any instruction to develop athletic ability. Conclusions that outgoing individuals possess more athletic ability could be grossly inaccurate (Boyd & Bee, 2006).

Due to the difficulty found in the previous two illustrations, most research involves fraternal and identical twin sets for the following reasons:

•Fraternal twins raised together show a correlation with a shared environment but not agenetic sameness.

•Identical twins raised apart as adoptees show correlations for non-shared environmentsbut a shared genetic foundation.

One such study examined the influences of heredity and environment on the differences of children’s conversational language use among twins. The study measured language skills with two standardized tests among 380 twins. According to the study, more than half of the variance in conversational language skills can be attributed to genetics. Additionally, evidence was not found to support significant shared environmental influence. This study sheds new light on this issue. Previously, differences were attributed to environmental influences such as premature birth and low birth weight (DeThorne et al., 2008).


“To be born and die are common to all animals, but there are specifically diverse ways in which these phenomena occur.” (Aristotle, trans. 1984). How humans grow and mature behaviorally is important in understanding the impact heredity, shared and non-shared environmental experiences have on humans. As humans age behavioral social-environmental and psychological changes emerge in a direct correlation with cultural and environmental influences. Environmental, heredity and behavioral genetics all give rise to “obesity, pre-diabetes, atherosclerosis, cancer, immune-suppression, menopause, and osteoporosis”

(Biological, Social-Environmental, and Psychological Dialecticism: An Integrated Model of Aging, 2000). As well with age innate biological changes impact our brain based on both shared and non-shared environmental experiences. A keen understanding of morbidity, mortality and how genetics influence both health and behavior are all important factors in how biological changes in the brain are associated with each stage of aging. Human behavior can be influenced by genetic pre-dispositions as well as shared and non shared environmental experiences each of these forces account for physical changes and/or declines throughout adulthood.


Blumenthal, H. T. & Von Dras, D. D. (2000). [University of Phoenix e-Text].

Biological, Social-Environmental, and Psychological Dialecticism: An Integrated Model of Aging. Lawrence Erlbaum Associates Inc.

Boyd, D., & Bee, H. (2006). Lifespan Development (4th ed.). Upper Saddle River, NJ: Allyn &Bacon, Inc. A Pearson Education Company.

DeThorne, L., Petrill, S., Hart, S., Channell, R., Campbell, R., Deater-Deckard, K., Thompson, L. A., & Vandenbergh, D. (2008). Genetic effects on children’s conversational language use. Journal of Speech, Language & Hearing Research, 51 (Issue 2), Retrieved June 4, 2008, from EBSCOhost database.

Lehrman S., (1998). DNA & behavior: the topic in-depth. Retrieved June 6, 2008, from, J. (2008, September 16). Behavioral Genetics. Retrieved April 8, 2009, J., (n.d.). Psychology 230. Retrieved May 20, 2008, from

Sandrock, J. (2002). Life-Span Development: A topical approach. McGraw-Hill HigherEducation. Retrieved April 7, 2009, from, S. & McCartney, K. (1983, April). How people make their own environments: a theoryof genotype → environment effects. Child Development. Vol. 54 Issue 2, p424, 12p.

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