The study of genetics has grown out of a desire to understand how exactly the individual comes to be just that, an individual different from its peers. In order to comprehend the scope of possible outcomes and how they came to be behavioral genetics looks at a number of variables; these include the impact of our genes (nature), and our environment (nurture). A countless number of hypotheses were put to the test through research to analyze the degree of influence of each. In this paper, team A will discuss the methods of behavioral genetics, the various research techniques used, their testing populations and why used, along with proposed answers and explanations.
Behavioral GeneticsBehavioral geneticists uses family, twin and adoption studies as a basis for their argument of individual differences (Lerner, Bearer, Garcia, & Coll, 2004). A significant contributor to studies in behavioral genetics, provides this definition: “Behavioral genetics is the genetic study of behavior, which includes quantitative genetics (twin and adoption studies) as well as molecular genetics (DNA studies) of human and animal behavior broadly defined to include responses of the organism from responses measured in the brain such as functional neuro-imaging to self-report questionnaires” (Plomin,2004).
One of the first twin studies was conducted by Bouchard in 1979 when he found a set of monozygotic twins, babies from a fertilized egg that splits into two. The babies were separated at a few weeks old. The babies had many physiological and psychological similarities. Since Bouchard’s initial study it has been proven that, while monozygotic twins raised together have many similarities, those separated at an early age have an even greater likeness. Since twins being raised together are more likely to highlight their differences in order to maintain some element of independence, behavioral geneticists argue that this indicates a strong genetic underpinning in human development (Plomin, 2004).
Research conducted by Grilo and Pogue-Geile (1991) correlated the familial relationships with extroversion. The study included monozygotic twins reared together and apart, dizygote twins reared together and apart, biological parents and children, biological siblings, adoptive parents and children and unrelated siblings reared together. The results reflected that the highest correlation was between monozygotic twins raised together and apart. The lowest correlation was between unrelated siblings raised together. For behavioral geneticists, these results conclude that genetics are at work in determining the extroversion of a person.
Behavioral geneticists suggest reasonable doubt in assuming connections between psychological environments and developmental results may be genetically arbitrated and that the environment a person is in responds to the genetically influenced characteristics (Plomin, 2004). The genetic association between parent and child is useful to examine. For example, “…differences in parenting can be the genetic effect rather than the environmental cause of children’s psychopathology” (Plomin, 2004, p. 345). The results of the twin, adoption and family studies support these assumptions.
The Correlation of Heredity and EnvironmentThe nature versus nurture controversy exists because some people believe that a person’s genetics has the greatest impact on their personality, intelligence and behavior. On the flipside, some people believe that the environment has more of an impact. Behavior geneticists assume that behavior is influenced by the relations of heredity and environment. With the help of twin studies, and adoption studies researchers are working on understanding what molds a person into the individual he or she is today.
Twin studies, using identical twins, are conducted to understand how biology influences traits and psychopathology in humans whose genotypes are the same (Haimowitz, n.d.).Twin studies also use fraternal twins who share half of the genes they acquire at conception which helps to compare the degrees of genetic influence such as intelligence and personality.
Adoption studies take a look to see if adoptive children exhibit the behavioral and psychological traits of their adoptive parents, or those of their biological parents (Haimowitz). Any links to biological parents can be attributed to genetics, and any connection to adoptive parents can be attributed to environment.
Heredity-Environment correlations can be shown in three ways. One is the passive genotype-environment correlations. Passive genotype-environment correlation exists when a child’s biological parents are raising him or her (MacDonald, n.d.). An example of this situation could be Ana’s parents having the genetic predisposition to be intelligent and read skillfully leading one to believe that Ana will more than likely share these skills.
Evocative Genotype-Environment Correlation occurs when a child’s genotype provokes a specific type of physical or social environment (MacDonald, n.d.). An example of this type of correlation: Andrew is artistic, and outgoing, he will elicit encouragement to try out for plays. Sheena is very athletic and competitive; she will be encouraged to go out for sports.
Active genotype-Environment Correlations emerge when a child seeks out environments he or she will find compatible and stimulating (MacDonald, n.d.). An example could be that a child like Matilda, who has a gift of music, will seek a musical environment where she can expand on her talent. Scientist researching how genetics influences academic achievements show three ways heredity and environment could possibly be correlated. The three ways in which Meredith Phillips and a team of colleagues found genetics and environment to be correlated are passive correlation, active correlation, and reactive correlation.
“Passive correlation: genes influence both a child’s environment and heredity (Phillips, Brooks-Gunn, Crane, Duncan, & Klebanov, n.d., ¶ 3).” “Active correlation: genes influence the environments that a child seeks out (Phillips et al., ¶ 3).” “Reactive correlation: environments react differently to people with different genetic profiles (Phillips et al., ¶ 3).” In passive correlation if a parent is the type of person whom enjoys reading, the love for reading could be transferred to the child from the parent reading to the child frequently. The child will already have the genetics from the parents.
My son enjoys music I would like to think he received that from me because of my interest in music. He hears a great deal of music when at home therefore, the music rich environment my son is placed in has an influence on his musical achievements. Combined with the genetic aspect of my love for music and his father’s love for music the affect of his music rich environment causes a stronger influential desire to be involved in music.
In active correlation, the child has genetic influences from the parent reading to him or her. When the child voices the desires for the parent to read to him or her, the parent enjoying the reading ultimately influences the child by reading to the child. The child requesting stories to be read is the incentive the parent has to continue the process along with the parent’s love for reading.
Reactive correlation was described as genetics affecting the child’s physical features with the child’s features being judged by peers. The views of the child’s peers are voiced and in the process the child’s academic achievements are effected. The child’s environment can put him or her under a certain labels. In this situation genetics affects the views of the child’s peers and the environment combined with genetics can have a negative affect on the child’s academics.
Definition of Shared and Non-shared Environmental ExperiencesBeyond genetics, each individual has a unique personality that is based on a blending of their shared and non-shared experiences in life. Shared environmental experiences are those which the majority of the world encounters. Shared experiences can occur differently by culture, but generally adhere to a specific “social clock or a set of age norms that defines a sequence of normal life experiences (Boyd & Bee, p. 10).” For American culture think of the traditions of school, watching a baseball game, having a BBQ, getting married, having children, working and retiring as relative shared norms that all, or most of us, encounter.
Of course, non-shared experiences are different for each of us; these are categorized as individual experiences. Individual or non-shared experiences can be influenced by “race, socioeconomic status, and other social factors (Boyd & Bee, 2006, p. 36).” These individual differences can also be related to school, relationships, marriage and childbirth and the unique perspective that each person has. Each individual thinks much differently and so the way that they perceive and interact in the world will make their experiences, shared and non-shared, unique to them.
Role Played by Shared and Non-shared Environmental Experiences DevelopmentThe importance that shared and non-shared experiences have in development is that they help shape our personal development as well as our social development. If in fact, each person encounters shared experiences in accordance with the norm expected, they are more likely to fit in culturally and have a higher understanding of appropriate and healthy relationships. Likewise, with non-shared experiences if interactions each person has with their parents and peers, and in his or her independent life, is healthy they will know themselves internally and process environmental factors that occur around them in a healthy manner. If the shared and non shared experiences of an individual do not go according to the norms of society it will be more difficult for them to develop into healthy adults who function both independently and interdependently at appropriate levels. (Boyd & Bee, 2006, p. 36)
In conclusion, behavioral geneticists have used a wide array of approaches to their research in developmental theories. Through the use of identical twins a great deal of information has been acquired on the basis of both genetics and environment. The strongest proponent of this argument was shown to be the case of identical twins separated at birth exhibiting very similar characteristics even though they had not been raised in the same environment. Corresponding research which also strengthens this argument shows that adoptive children exhibit very few of the characteristics of their adoptive parents. It seems safe to say that genetics lay the foundation of behavior with environment and individual experience capable of exhibiting some influence beyond that.
Boyd, D., & Bee, H. (2006). Lifespan Development. Retrieved from http://ecampus.phoenix.eduGrilo, C. M., & Pogrue-Geile, M. F. (1991). The Nature of Environmental Influences on Weight and Obesity: A Behavior Genetic Analysis [White paper]. Retrieved from National Institute of Health: http://www.pubmedcentral.nih.govHaimowitz, A. G. (n.d.). Heredity versus Environment: Twin, Adoption, and Family. Retrieved April 21, 2009, from http://www.personalityresearch.org/papers/haimowitz.htmlLerner, R. M., Bearer, E. L., Garcia, , & Coll, C. G. (2004). Nature and Nurture: the Complex Intereplay if Genetic and Environmental Influences on Human Behavior and Development. . Retrieved from http://books.google.com/books?id=iFriCJCTsx4C&printsec=frontcoverMacDonald, K. (n.d.). PSYCHOLOGY 361: BEHAVIOR GENETICS. Retrieved April 21, 2009 , from http://www.csulb.edu/~kmacd/361Notes2.htmlPhillips, M., Brooks-Gunn, J., Crane, J., Duncan, G. J., & Klebanov, P. (n.d.). How Might Genetic Influences on Academic Achievement Masquerade as Environmental Influences?. Retrieved April 22, 2009, from http://www.children.smartlibrary.org/NewInterface/segment.cfm?segment=2606Plomin, R. (2004). Genetic and Developmental Psychology. Merrill-Palmer Quarterly, 50(3), 341-352. Retrieved from http://muse.jhu.edu/login?uri=/journals/merrill-palmer_quarterly/v050/50.3polmin.html