A large part of the evidence collected linking genetics and the environment to personality comes from twin studies, which compare levels of similarity in personality between genetically identical twins. Genetics : The expression of inherited genes plays a role in determining personality.
In the field of behavioral genetics, the Minnesota Study of Twins Reared Apart—a well-known study of the genetic basis for personality—conducted research with twins from to These findings suggest the heritability of some personality traits, implying that some aspects of our personalities are largely controlled by genetics. Multiple twin studies have found that identical twins do have higher correlations in personality traits than fraternal twins. While identical twins may have some similar personality traits, however, they still have distinct personalities, suggesting that genetics are not the only factor in determining personality.
One study measuring genetic influence on twins in five different countries found that correlations for traits between identical twins were 0.
Many personality studies today investigate the activation and expression of genes and how they relate to personality. How DNA interacts with the environment determines what part of the DNA code is actually activated within an individual—in other words, which genes will be expressed.
The biological approach to personality has also identified areas and pathways within the brain that are associated with the development of personality.
A number of theorists, such as Hans Eysenck, Gordon Allport, and Raymond Cattell, believe that personality traits can be traced back to brain structures and neural mechanisms, such as dopamine and seratonin pathways.
Researchers using a biological perspective will seek to understand how hormones, neurotransmitters, and different areas of the brain all interact to affect personality. One of the first documented cases that demonstrated the link between personality and the brain was that of Phineas Gage. In , Gage was working as a blasting foreman for a railroad company. Due to a faulty blast, a railroad spike was blown through his head; miraculously, he survived the accident.
One strength of the biological perspective is its strict adherence to scientific methodology. All factors are reduced to quantifiable variables that can be reliably measured by personality trait models and questionnaires. The personality measures are standardized across measurements, and these measures of personality are very compatible with statistical analyses, providing an easily administered and measurable definition of personality.
This method can also be deterministic, meaning that some factors are identified as causal—i. Because of this, the biological perspective can be useful in identifying causes of and effective treatments for personality and mood disorders. For example, identifying seratonin imbalance as a cause of depression led to the development of selective seratonin reuptake inhibitors SSRIs , which have been found to be an effective treatment for depression.
A limitation of this perspective is that it focuses almost exclusively on the nature side of the nature vs. Because of this exclusive focus, other factors that are integral to personality are not included. Hormones, neurotransmitters, and genetics are the key factors in this focus; the effects of environmental and social factors, however, are often overlooked. Twin studies have shown that heritable factors are not the only predictor of personality or even diseases such as schizophrenia; the biological perspective does not fully address non-heritable factors.
Furthermore, genetic factors always work with environmental factors to create personality. For example, a person may have a genetic variant that is known to increase his or her risk for developing emphysema from smoking. But if that person never smokes, then emphysema most likely will not develop.
Perhaps the most direct way to study the role of genetics in personality is to selectively breed animals for the trait of interest. In this approach the scientist chooses the animals that most strongly express the personality characteristics of interest and breeds these animals with each other. If the selective breeding creates offspring with even stronger traits, then we can assume that the trait has genetic origins. In this manner, scientists have studied the role of genetics in how worms respond to stimuli, how fish develop courtship rituals, how rats differ in play, and how pigs differ in their responses to stress.
Although selective breeding studies can be informative, they are clearly not useful for studying humans. For this psychologists rely on behavioural genetics — a variety of research techniques that scientists use to learn about the genetic and environmental influences on human behaviour by comparing the traits of biologically and nonbiologically related family members Baker, Behavioural genetics is based on the results of family studies , twin studies , and adoptive studies.
The presence of the trait in first-degree relatives parents, siblings, and children is compared with the prevalence of the trait in second-degree relatives aunts, uncles, grandchildren, grandparents, and nephews or nieces and in more distant family members.
The scientists then analyze the patterns of the trait in the family members to see the extent to which it is shared by closer and more distant relatives. Although family studies can reveal whether a trait runs in a family, it cannot explain why. In a twin study , researchers study the personality characteristics of twins. Twin studies rely on the fact that identical or monozygotic twins have essentially the same set of genes, while fraternal or dizygotic twins have, on average, a half-identical set.
The idea is that if the twins are raised in the same household, then the twins will be influenced by their environments to an equal degree, and this influence will be pretty much equal for identical and fraternal twins. In other words, if environmental factors are the same, then the only factor that can make identical twins more similar than fraternal twins is their greater genetic similarity. In a twin study, the data from many pairs of twins are collected and the rates of similarity for identical and fraternal pairs are compared.
A correlation coefficient is calculated that assesses the extent to which the trait for one twin is associated with the trait in the other twin. Twin studies divide the influence of nature and nurture into three parts:. In the typical twin study, all three sources of influence are operating simultaneously, and it is possible to determine the relative importance of each type.
An adoption study compares biologically related people, including twins, who have been reared either separately or apart. Evidence for genetic influence on a trait is found when children who have been adopted show traits that are more similar to those of their biological parents than to those of their adoptive parents.
Evidence for environmental influence is found when the adoptee is more like his or her adoptive parents than the biological parents. The results of family, twin, and adoption studies are combined to get a better idea of the influence of genetics and environment on traits of interest. Table 4. If you look in the second column of Table 4. This column represents the pure effects of genetics, in the sense that environmental differences have been controlled to be a small as possible.
You can see that these correlations are higher for some traits than for others. You can also see from the table that, overall, there is more influence of nature than of parents. Identical twins, even when they are raised in separate households by different parents column 4 , turn out to be quite similar in personality, and are more similar than fraternal twins who are raised in separate households column 5. These results show that genetics has a strong influence on personality, and helps explain why Elyse and Paula were so similar when they finally met.
Despite the overall role of genetics, you can see in Table 4. You might at first think that parents would have a strong influence on the personalities of their children, but this would be incorrect.
As you can see by looking in column 7 of Table 4. Shared environment does influence the personality and behaviour of young children, but this influence decreases rapidly as the child grows older.
What this means is that although parents must provide a nourishing and stimulating environment for children, no matter how hard they try they are not likely to be able to turn their children into geniuses or into professional athletes, nor will they be able to turn them into criminals.
If parents are not providing the environmental influences on the child, then what is? The last column in Table 4. You can see that these factors — the largely unknown things that happen to us that make us different from other people — often have the largest influence on personality.
They explain that each niche has an ideal personality type, a person who wishes to be a loner might not want to live in New York City, for example. Niches are made up of occupational, social and other specializations of life like hobbies and clubs. They hoped to test the theory that societies that are more complex, with multiple niches, will also have greater diversity in personality types. In psychology, personality traits are often discussed in reference to the Big Five.
This group of dimensions has long been used by psychologists to universally define human personality structure. Yet no one really knows why the Big Five might best represent the structure of human personality, it just seems to fit the data. But what happens when it doesn't fit the data? Most critiques are explained away by Big Five advocates as being merely methodological. We wanted to see if we can build from the ground-up a more theoretical basis for why personality structure might vary across populations.
It is our personality that makes us who we are, but how exactly do our personalities form? Personality development has been a major topic of interest for some of the most prominent thinkers in psychology. Since the inception of psychology as a separate science, researchers have proposed a variety of ideas to explain how and why personality develops.
Personality development refers to how the organized patterns of behavior that make up each person's unique personality emerge over time. Many factors go into influencing personality, including genetics , environment, parenting , and societal variables. Perhaps most importantly, it is the ongoing interaction of all of these influences that continue to shape personality over time.
Our personalities make us unique, but how does personality develop? How exactly do we become who we are today? What factors play the most important role in the formation of personality? Can personality ever change? To answer this question, many prominent theorists developed theories to describe various steps and stages that occur on the road of personality development.
The following theories focus on various aspects of personality development, including cognitive, social, and moral development. In addition to being one of the best-known thinkers in the area of personality development, Sigmund Freud remains one of the most controversial. In his well-known stage theory of psychosexual development , Freud suggested that personality develops in stages that are related to specific erogenous zones. Failure to complete these stages, he suggested, would lead to personality problems in adulthood.
Freud not only theorized about how personality developed over the course of childhood, but he also developed a framework for how overall personality is structured. According to Freud, the basic driving force of personality and behavior is known as the libido. This libidinal energy fuels the three components that make up personality: the id, the ego, and the superego. Freud's concept of the id , ego , and superego has gained prominence in popular culture, despite a lack of support and considerable skepticism from many researchers.
According to Freud, it is the three elements of personality that work together to create complex human behaviors.
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