Q. Effect of heredity and environment on the development of personality. Ans. What is Personality? Personality can be defined as a dynamic and organized set of characteristics possessed by a person that uniquely influences his or her cognitions, motivations, and behaviors in various situations. Some say that personality is inherited or hereditary. Some raised the idea that it is environment that shapes one’s personality. Both are correct, many studies have shown that both heredity and environment are responsible in shaping an individual’s personality. Heredity is one of the major factors in the development of our personality.

Hereditary factors were passed by our parents and ancestors to us. The individual’s talent and some other traits are just few examples of these traits. The environment is another factor in personality development. These include the place we live and the people around us. Our experiences in our day to day life, as well as the people whom we associated with such as our family, friends, people in the school, in the church and the community as a whole, all influences our personality. Behavioral and Social Cognitive Theories suggest that personality is a result of interaction between the individual and the environment.

Behavioral theorists include B. F. Skinner and Albert Bandura. Biological and Evolutionary Approaches to Personality suggests that important components of personality are inherited. Research on heritability suggests that there is a link between genetics and personality traits. One of the best known biological theorists was Hans Eysenck, who linked aspects of personality to biological processes. For example, Eysenck argued that introverts had high cortical arousal, leading them to avoid stimulation. On the other hand, Eysenck believed extroverts had low cortical arousal, causing them to seek out stimulating experiences.

Some researchers contend that specific genes are related to personality. For example, people with a longer dopamine-4 gene are more likely to be thrill seekers than are those without such a gene. These thrill seekers tend to be extroverted, impulsive, quick-tempered, and always in search of excitement and novel situations (Hamer et al. , 1993; Zuckerman & Kuhlman, 2000) Illustration of Effect of Hereditary and Environmental Factors on Personality: Twin studies are a vastly important tool in dissecting the nature versus nurture argument.

Identical twins, or monozygotic twins, are siblings whose genotypes are duplicates of each other. They are most likely the best indicator of whether biology affects traits and psychopathology in human beings. Fraternal twins, or dizygotic twins, share exactly half their genes with each other. They are not as optimal as identical twins for deciphering the degrees of genetic influence, but they are a very good basis for comparison for identical twins. Fraternal twins are similar to first-degree relatives, except they are sure to share the exact same age, as do identical twins.

Twin studies usually rely on samples of identical and fraternal twins; if biology has a greater hand than environment, then identical twins should behave or possess psychopathology similar to each other more so than fraternal twins (Plomin et al. , 1997). Identical twins reared apart are far more similar in personality than fraternal twins. These observations suggest that personality is heritable. However, the environment must also be looked at. There are two kinds of environmental effects: shared experiences and non-shared experiences.

Although identical twins are genetically identical and share the same family environment, identical twins raised together do not have identical personalities. These differences must then be explained entirely by non-shared environmental effects. * Attitudes: One particular study sought to determine the heritability of attitudes among twins, as well as the genetic variables, such as intelligence, that could affect attitudes among pairs of twins. A questionnaire was provided to the participants, in which they were asked to rate their personality traits, physical abilities, and physical attractiveness.

They were also asked to note their academic achievements (Olson et al. , 2001). The results of the study showed that differences between attitudes of the participants were at least partially correlated to genetic factors. It also showed that attitudes related to self-reported perspectives or to activities were often correlated. For instance, the survey asked subjects to rate themselves on the trait of sociability. That trait was correlated with 5 out of 6 attitude factors subjects had toward sociability. Attitudes toward athleticism highly correlated with findings on self-reported athletic abilities.

The causal model was expressly supported in these findings, because athletic skill (the mediator), for example, seemed to be linked with attitudes toward athleticism. Of course, this model is not without its problems: one cannot assume that X is the cause of Y in every single situation. Case in point: attitudes toward leadership seemed to be related to high self-ratings of physical attractiveness, sociability, and aggressiveness. Because of these numerous factors, it is still not possible to always accurately assume direct, singular relations between genetic traits and attitudes (Olson et al. , 2001).

Interestingly, non-shared environment experiences between pairs of twins seemed to be the strongest cause of attitude variances, overshadowing genetic predispositions as well as shared environment experiences (Olson et al. , 2001). Non-shared environment is a term used to refer to something in the environment that directly affects one twin but does not impact the other at all (Van den Oord, Boomsma, & Verhulst, 2000). The study did indicate that some non-shared environment experiences were very much connected to attitudes and self-reports of physical characteristics and intelligence (Olson et al. . * Genotype-Environment Interaction: Personality psychologists Auke Tellegen and colleagues at the University of Minnesota examined the personality traits of pairs of twins who were genetically identical but were raised apart from each other (Tellegen et. Al. , 1988, Bouchard et. Al. , 2004). In the study each twin was given a battery of personality tests, including one that measured eleven key personality characteristics. The results of the personality tests indicated that in major respects the twins were quite similar I personality, despite having separated at an early age.

Moreover, certain traits were more heavily influenced by heredity than were others. Example- social potency (the degree to which a person assumes mastery and leadership roles in social situations and traditionalism (the tendency to follow authority) had particularly strong genetic components, whereas achievement and social closeness had relatively weak genetic components. Table: The roots of personality. The percentages indicate the degree to which eleven personality characteristics reflect the influence of heredity. Traits| Percentage| |

Social potency| 61%| Is masterful; a forceful leader who likes to be centre of attention. | Traditionalism| 60%| Follows rules and authority; endorses high moral standards and strict discipline. | Stress reaction | 55%| Feels vulnerable and sensitive; is given to worrying and easily upset. | Absorption| 55%| Has vivid imagination readily captured by rich experience; relinquishes sense of reality. | Alienation| 55%| Feels mistreated and used, that “the world is out to get me. ”| Well-being| 54%| Has a cheerful deposition; feels confident and optimistic. Harm avoidance| 51%| Shuns the excitement of risk and danger; prefers the safe route even if it is tedious. | Aggression| 48%| Is physically aggressive and vindictive; has taste for violence; is “out to get the world. ”| Achievement| 46%| Works hard; strives for mastery; puts work and accomplishment ahead of other things. | Control| 43%| Is cautious and plodding; is rational and sensible; likes carefully planned events. | Social closeness| 33%| Prefers emotional intimacy and close ties; turns to others for comfort and help. | * Adoption Studies:

Adoption studies are important in studying heredity and environmental effects on human traits and psychopathology because they include two sets of factors that may account for differences in behavior, personality, and psychopathology: biological parents and environmental parents. Any links between the biological parents and the child that is given away is usually explained by genetics, and any links between the adoptive, or environmental parents, to the adopted child is usually attributed to environment (Plomin et al. , 1997). Schizophrenia

The first adoption study performed on schizophrenia showed that family environment contributes little to a child’s risk for a disorder such as schizophrenia. This study was performed through interviews of adopted-away children of biological mothers who suffered from schizophrenia, and interviews of adopted children whose birth parents did not suffer from any mental disorders. Several of the adopted away children of schizophrenic mothers suffered from schizophrenia themselves, while the adoptees whose parents didn’t have schizophrenia also did not have schizophrenia themselves.

This supports the theory that it doesn’t matter what specific environment a child is raised in; if its parent or parents suffer from a mental disorder, the risk for suffering from the same disorder will be equal regardless of if the child was raised with its biological parents or with its adoptive parents (Plomin et al. , 1997). Environmental factors also inevitably contribute to the development of schizophrenia. Infant Shyness An adoption study was conducted to disentangle the reasons behind why some infants are open and responsive to attention right away, some take time to open up, and still yet, some others are fearful and withdrawn.

It is difficult to tell whether babies are shy because their mothers are shy and thus do not take them out very much, or because the shy mothers pass down their shyness traits. Measures of this study attempted to clarify the relationship between the infants and adoptive and biological parental shyness, parental sociability, and parental introversion-extraversion (Daniels ; Plomin, 1985). Adoptive parents were given questionnaires that asked them to rate their infants’ shyness levels, and then to rate themselves on the traits listed previously.

It must be noted that the self-reported ratings of the biological were performed before the birth of the infants, and the scoring of the infants’ shyness were performed by the adoptive parents when the babies were two years old. The results showed that in non-adoptive families, the parents who reported high rates of shyness, low rates of sociability, and high rates of introversion also had shy infants. This was also seen in adoptive families whose parents rated similarly, indicating that a combination of home environment and genetics must come into play.

One significant conclusion was made in this study that was based on the fact that biological mothers rated high in shyness, and their adopted-away babies were also shy. This strengthens the possibility of a genetic link overshadowing family environment, but of course further research must be done (Daniels ; Plomin, 1985). * How Identical Twins Grow Up To Be Different: Attitudes, beliefs, and norms are constructed during adolescence and made more concrete over time (Harris, 1995).

This process of socialization most notably occurs through the contact that adolescents have with their peer groups. The theory of group socialization posits that the peer group and other outside-the-home socialization are responsible for shaping the personality of adolescents and teenagers (Harris, 1995). The fact that siblings reared in the same home environment have very distinct personalities could be attributed to each sibling’s different peer groups. Twins tend to stick together when they are in their adolescent and teenage years.

As a result of being together they would also share the same peer group. Combining these ideas and the group socialization theory, it seems logical that if twins share the same peer group then they would also share the same attitudes, beliefs, and norms. And if what we learn in our early years becomes a part of our personality, how could twins have different attitudes, beliefs, and norms when they are older? This question seems to relate more to MZ twins than to DZ twins, because DZ twins are comparable to normal siblings in that they only share half of their genes.

Perhaps the variance is greater for the non-shared environment because of the DZ twins, who are more apt to have different peer groups. Another explanation could be that both MZ and DZ twins had individual life experiences that changed how they thought and what they believed. Genetic and environmental influences on observed personality: Evidence from the German Observational Study of Adult Twins: Previous behavior-genetic research on adult personality relied primarily on self-reports or peer reports that may be subject to contrast effects, resulting in biased estimates of genetic and environmental influences.

In the German Observational Study of Adult Twins (GOSAT), personality traits of 168 monozygotic (MZ) and 132 dizygotic (DZ) twin pairs were rated on 35 adjective scales, largely markers of the Big 5. The ratings were provided by 120 judges who never met the twins but observed videotaped behaviors of 1 twin of each pair in 1 of 15 different settings. The aggregated video-based trait ratings were highly reliable, and substantial correlations were obtained between MZ as well as DZ twins. Model-fit analyses suggested about 40% genetic, 25% shared environmental, and 35% non-shared environmental influence.

Extraversion was the only trait that seemed not to be influenced by shared environment. Conclusion: Identification on specific genes linked to personality, coupled with the temperaments that infants are born with, hardly means that a person is destined to have certain types of personality. Firstly, it is unlikely that any single gene is linked to a specific trait. For instance, the dopamine-4 receptor accounts for only around 10 percent of the variation in novelty seeking between different individuals.

The rest of the variation is attributable to other genes and environmental factors (angier, 1996; Keltikangas-Jarvinen et. Al. , 2004; Lahti et. Al. , 2005) Hence, it is clear from the brief summaries provided on twin, adoption, how identical twins grow up to be different and evidence from the German Observational Study of Adult Twins it is clear that for some cases, genetics seem to dominate; in some other cases, environment explains it all. In still more situations, it is a strong combination of the two factors that mold people to be who they are.

So, even if more genes are found to be linked to specific personality characteristics, genes still cannot be viewed as the sole cause of personality. Thus genetically determined characteristics may not be expressed if they are not “turned on” by particular environmental factors. References: http://www. personalityresearch. org/papers/haimowitz. html http://psychology. about. com/od/psychologystudyguides/a/personalitysg_3. htm http://psycnet. apa. org/index. cfm? fa=buy. optionToBuy&id=2001-00201-010&CFID=5390913&CFTOKEN=61692629%29. Understanding Psychology (Book), Eight Edition, Robert S. Feldmen