Nature vs. Nurture in the Development of Personality
Personality has been defined as the dynamic organization within the individual of those psychophysical systems that determine his unique adjustments to his environments (Allport, 1937). The most popular view on personality is through a trait approach. This is due largely to consistency at the level of traits of behavioral aggregates. In the same way personality is conceptualized in terms of individual differences in behavioral dispositions (Borkenau, Riemann, Spinath, Anglietner, 2006). The individual differences of persons as seen in the level of specific traits gives a window of opportunity for research in the variety of traits which individuals possess. Research may focus as well on the factors propelling change in personality traits of individuals.
Personality research has, over the past years, focused on determinant factors in personality or trait development through a dichotomous lens. The consistency of traits over the lifetime of an individual encourages the grounding of nature and nurture studies. Since personality is deemed constant, the determinant factors of the same may be limited in range, thus also the reason why in most nature-nurture studies the focus has been the zygote and young children.The nature-nurture dichotomy has propelled research in both the hereditary and environmental influence field. However, as both ends progress in findings the wall delineating the dichotomy is worn thin. Personality may not be so easily explained as the consequence of mere genetics or even as the result of external influences, rather it may be the complex output of the interaction of these two supposedly opposing sides.
Nature: The Genetic Inheritance
Behavioral geneticists have been concerned in the collection of evidence that personality traits rely on built-in morphological make-up. They seek to show the comparative influence of genes and the environment and employ the concept of heritability of genes to quantify their work (Mullen, 2006). Behavioral scientists on this side of the spectrum therefore see personality as a result of the biological make-up of a person and rely heavily on DNA codes to predict a person’s behavioral responses to stimuli. Variations in responses or changes in personality may then be attributed to inclinations for the same resulting from inherited traits.
Behavioural genetics has been defined as the genetic study of behavior. The methods employed by behavioral geneticists have included quantitative genetics, which deal with twin studies and adoption studies, as well as molecular genetics, which deal with DNA studies (Plomin, 2000). Molecular genetics has considered not only the study of human but also of animal behavior. The method includes the recording of organism responses and the comparison of the same with responses measured in the brain through functional neuroimaging to self-report questionnaires (Plomin, 2000).
While true that molecular biology holds the future of human genetics, little of what is known regarding personality has resulted from the same. Most of what behavioral geneticists have learned have resulted from twin-studies (Powledge, 1993). Twin studies are grounded on the bases that there are two types of twins. Monozygotic twins or identical twins result from the splitting of a single fertilized egg while Dizygotic twins or fraternal twins are a product of two separate fertilized eggs (Powledge, 1993). As a result, monozygotic twins share all of their genes or are exact duplicates of one another. Dizygotic twins on the other hand, share only half of their genes, just as ordinary siblings do (Powledge, 1993). Behavioral geneticists have therefore relied on the similarities of monozygotic twins to conclude that if a trait is observed more frequently in both members of a monozygotic pair than in members of a dizygotic pair, then the trait is genetically influenced.
A popular form of the twin study is research done with monozygotic twins who were reared apart while young. Since twin studies presume that environment has less influence on monozygotic twins, the subsequent presumption of rearing monozygotic twins apart would be that they would still possess similar traits. Behavior geneticists go so far as to state that because monozygotic twins reared apart share essentially no environmental influences, the correlation of similar traits between them is a direct estimate of heritability (Waller, Kojetin, Bouchard, Lykken, ; Tellegen, 1990). Several studies have shown correlations between members of monozygotic pairs who had been raised apart from each other. Studies had even shown that such correlation persisted even if the members had no knowledge of the existence of their twin. Such findings support the theory of behavior geneticists that personality is influenced by genes since the correlation between monozygotic twins are not attributable to shared environments, as in fact there was no environment shared by them (Hermstein ; Murray, 2004).
One criticism of twin studies is the inability of studies to produce 100% concordance in identical twins. Although percentages are significant different for monozygotic twins’ similarities than dizygotic twins, the fact remains that there is still a percentage of monozygotic twins who possess discordant or dissimilar traits. The very basis of conducting twin studies is the 100% similarity in genes of monozygotic twins. The genes of such twins are said to be completely identical. Following such reasoning, it should necessarily follow that if personaliity were the product merely of inherited genes then both members of monozygotic pairs should possess personality traits possessed by any one member individually.
Nurture: The Environmental Influence
Behavioral scientists focusing on the nurture side of the debate advocate that personality is a result of the individual’s environment. Personality thus results from the context in which the individual finds himself. It is said that social roles are comprised of expectations and normative behaviors that emerge from the psychological meanings attributed to situational contexts (Matsumoto, 2007). The meanings from which expectations are derived are culture-specific.
Culture, on the other hand, arises from the interaction of human nature with specific environmental contexts wherein groups work in these meanings are cultural. Culture, in turn, emerges from the interaction of basic human nature with specific ecological contexts in which groups exist through a process of environmental adaptation (Matsumoto, 2007). One manner to view this process of adaptation is in the perspective of the evolutionary standpoint. Individuals tend to behave in the manner that would ensure their basic needs and survival. Thus it is the environment that dictates and limits the movement of individuals as they are driven by physiological needs, not genetically-wired inclinations.
Matsumoto illustrates such a point with the well-known situation of persons fearing spiders, snakes, sharks and the like (2007). Such fears are not results of inherited phobias. Rather, they are responses to stimuli which are identified as harmful to individuals. In essence, it is held that the culture of a specific area and the situational context determine the manner in which an individual responds. Repeated exposure to similar situations would thus result to similar responses while responses leading to negative consequences would cause the alteration of responses to a similar situation that would subsequently arise. It is the repetition of the behavior or the pattern of fluctuating responses in accordance to differing stimuli and effects which is deemed as personality. Therefore, unlike nature claims, this element on the argument for the side of nurture delimits genetics to mere inclinations in terms of physical make-up and drives for needs.
It is to be noted that behavioral scientists have also grounded their research on biological bases and even on genetic motivations. They have gone so far as to study the placental environments of embryos to ascertain the factors affecting similarities and differences in twins. It was found that monozygotic twins share only one placenta making them more prone to harm (Phelps, Davids, ; Schartz, 1997). The sharing of one placenta necessarily meant that nutrients and proteins entering into the placental fluid would be shared by the twins inside it. However, there is no assurance or mechanism to ensure that the sharing of nutrients is equal. Therefore, the consumption of one in greater quantities necessarily means that the other member of the pair has less to draw upon. Behavior therefore that is beneficial to another, if in excess of the norm, would be harmful to another. Or given the scenario that insufficient nutrients enter into the placenta, the adequate consumption of one would lead to malnutrition on the part of the other. Such an environment is said to point more poignantly at the resulting differences in monozygotic twins than in their similarities (Phelps et al., 1997). Thus, differences and similarities in traits and resulting personalities of twins would be attributable more to environmental factors than to genetic inclinations.
One method to ascertain the role of environment is the utilization of “nonshared environments” to extract the situational dynamics certain individuals are exposed to (Powledge, 1993). Such studies have been utilized to parallel the twin studies banked on by nature advocates. Nonshared environments focus on family contexts and the effect of exposure of family members to different environments. Twin studies also prove useful herein as it is shown that behavior differences in twins may be answered by the environments such pairs are exposed to separately. Therefore, although living together and sharing the same experiences, pairs may still have specific environments which they do not share. These environments control in part certain personalities and behaviors of the member exposed to the same.
Research Studies: The Debate as Applied to Specific Traits
To illustrate the theoretical points of the two sides to the nature vs. nurture debate, a closer look is taken at two particular traits. While arguments for a particular trait may be made by both sides, both raising valid arguments, it is still important to look at the particular application that one side has made regarding its method and concept.
One of the studies conducted utilizing the theory of nonshared environments focused on the inclination of individuals to become alcoholics. The study postulated that changes in environment can moderate genetic influences on the inclinations of individuals to fall into excessive drinking patterns. The study showed that genes influenced drinking less in married women than in single women (Powledge, 1993). The study based its finding on the fact that single women were more available to party with friends where drinking was invariably a social function. Unlike married women whose role as wife or mother require their presence at home more often than single women. Thus, it was shown that although genes played a part in the tendency of the women to become alcoholics, the genetic biases did not tell the whole story. In fact, genetic tendencies were inhibited and controlled for by the situational contexts in which the individuals found themselves.
Anorexia nervosa is an eating disorder characterized by a markedly low appetite and tendencies to lessen food intake as a result of perceived unattractiveness due to being overweight. Such behaviors result in forced vomiting, excessive dieting and the like (Crisp, Hall, ; Holland, 1985). In the present study under discussion, twin studies were undertaken to ascertain whether genetic motivations determined the expression of the said disorder. The findings showed that out of the population studied, nearly half of the monozygotic pairs displayed concordance in being diagnosed with anorexia nervosa whereas in the dizygotic pairs only 7% were found to be concordant. Such results were found to be significant (Crisp et al., 1985). The study further took into account the common symptoms accompanying anorexia nervosa and determined that the individual symptoms were controlled by different genetic strands. Thus, it was concluded that the inclinations for anorexia nervosa as a genetically motivated disease were controlled by combinations of varying genetic strands.
In spite of these findings however, research has also found that anorexia nervosa may result from experiential factors such as psychological maturational challenges (Crisp et al., 1985). It cannot be denied that the feelings of inadequacy nurtured by anorexics result in part from societal stigmas that may have been imposed upon them in the past. Such a case would be apparent in a young obese child always warned by her mother and compared with other young girls her age. Even if such child outgrows her childhood obesity and develops a figure that is attractive or acceptable by the norm, the stigma placed upon her during her early years might foster still the feelings of inadequacy (Crisp et al., 1985).
Although both sides to the debate have been persuasive in their arguments and research, the emerging conclusion gravitates toward the middle ground. Take into point the eating disorder anorexia nervosa, Although geneticists found a basis for their arguments, the environmental factors that affected the emotive causes of the disease could not be dispelled. The same observation can be made of many behavioral studies aiming to ascertain genetic biases. However, the counter is also found to be true. In studies showing that environmental factors mold the emergence of behavior, the built-in inclinations toward certain behaviors and personality traits are not refuted. Further, molecularbiology and neuropsychology have found genetic and biological bases for personality and have further shown that the stimulation of certain areas of the brain or the alteration of certain nuclear functions produce changes in personality.
It is argued that although responses to given situations may change invariably, personality is still constant over time. Such an argument can only be based on natural theories while the contextual differences observed may be attributed to nurture. It is the interaction of both genetic and environmental factors that encapsulates the bases for personality traits. The external stimuli introduced by varying environments do not result in responses that cannot be contained by biological make-up or genetic inheritance. An individual’s genes therefore provide a lay-out or a blueprint upon which environmental factors are plotted to produce given appropriate responses. On its own, genetic tendencies without stimuli are left latent and may not even appear to be present. A firm grasp of both perspectives is needed therefore in order to fully comprehend the development of personality.
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