One Genetic Factor That Can Influence Your Personality is __________

One Genetic Factor That Can Influence Your Personality is __________

Chapter 12. Personality

12.3 Is Personality More than Nature or More Nurture? Behavioural and Molecular Genetics

Learning Objectives

  1. Explain how genes transmit personality from one generation to the next.
  2. Outline the methods of behavioural genetics studies and the conclusions that we tin can draw from them nearly the determinants of personality.
  3. Explain how molecular genetics research helps united states empathize the part of genetics in personality.

One question that is exceedingly important for the study of personality concerns the extent to which it is the outcome of nature or nurture. If nature is more of import, so our personalities volition form early in our lives and will be difficult to change after. If nurture is more important, however, then our experiences are likely to be particularly important, and we may be able to flexibly change our personalities over fourth dimension. In this section we will see that the personality traits of humans and animals are determined in large function by their genetic makeup, and thus it is no surprise that identical twins Paula Bernstein and Elyse Schein turned out to be very like even though they had been raised separately. Merely we volition likewise meet that genetics does not determine everything.

In the nucleus of each cell in your body are 23 pairs of
chromosomes. One of each pair comes from your male parent, and the other comes from your mother. The
chromosomes

are made up of strands of the molecule DNA (deoxyribonucleic acid), and the Dna
is grouped into segments known equally
genes. A
gene
is
the basic biological unit that transmits characteristics from one generation to the next. Homo cells have most 25,000 genes.

The genes of different members of the same species are almost identical. The DNA in your genes, for instance, is about 99.9% the same as the Deoxyribonucleic acid in my genes and in the Dna of every other man being. These common genetic structures lead members of the aforementioned species to be built-in with a variety of behaviours that come naturally to them and that define the characteristics of the species. These abilities and characteristics are known as
instinctscircuitous inborn patterns of behaviours that aid ensure survival and reproduction
(Tinbergen, 1951). Different animals have different instincts. Birds naturally build nests, dogs are naturally loyal to their man caretakers, and humans instinctively learn to walk and to speak and understand language.

But the strength of dissimilar traits and behaviours also varies within species. Rabbits are naturally fearful, but some are more fearful than others; some dogs are more loyal than others to their caretakers; and some humans learn to speak and write better than others exercise. These differences are determined in function by the pocket-size amount (in humans, the 0.one%) of the differences in genes amidst the members of the species.

Personality is non determined by any single gene, only rather past the actions of many genes working together. At that place is no “IQ factor” that determines intelligence and there is no “expert matrimony-partner cistron” that makes a person a particularly expert wedlock bet. Furthermore, fifty-fifty working together, genes are not then powerful that they tin can control or create our personality. Some genes tend to increase a given characteristic and others piece of work to decrease that same characteristic — the complex relationship among the various genes, as well as a variety of random factors, produces the final outcome. Furthermore, genetic factors always work with environmental factors to create personality. Having a given pattern of genes doesn’t necessarily mean that a detail trait will develop, because some traits might occur only in some environments. For example, a person may have a genetic variant that is known to increase his or her take chances for developing emphysema from smoking. But if that person never smokes, then emphysema most likely volition not develop.

Studying Personality Using Behavioural Genetics

Perhaps the nigh direct way to study the role of genetics in personality is to selectively brood animals for the trait of interest. In this approach the scientist chooses the animals that about strongly express the personality characteristics of involvement and breeds these animals with each other. If the selective convenance creates offspring with even stronger traits, then we can assume that the trait has genetic origins. In this manner, scientists take 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 exist informative, they are conspicuously not useful for studying humans. For this psychologists rely on
behavioural geneticsa variety of research techniques that scientists apply to learn about the genetic and environmental influences on man behaviour by comparing the traits of biologically and nonbiologically related family members
(Baker, 2004). Behavioural genetics is based on the results of
family studies,
twin studies, and
adoptive studies.

A
family studystarts with one person who has a trait of interest — for instance, a developmental disorder such equally autism — and examines the individual’s family tree to determine the extent to which other members of the family also accept the trait. The presence of the trait in first-degree relatives (parents, siblings, and children) is compared with the prevalence of the trait in second-caste 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 encounter the extent to which it is shared by closer and more distant relatives.

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Although family studies can reveal whether a trait runs in a family unit, it cannot explain why. In a
twin study,

researchers written report the personality characteristics of twins.
Twin studies rely on the fact that identical (or monozygotic) twins have substantially the aforementioned set of genes, while fraternal (or dizygotic) twins accept, on boilerplate, a half-identical set up. The thought is that if the twins are raised in the aforementioned household, then the twins volition be influenced by their environments to an equal degree, and this influence will exist pretty much equal for identical and fraternal twins. In other words, if environmental factors are the same, then the only factor that can brand identical twins more than similar than fraternal twins is their greater genetic similarity.

In a twin report, 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:

  • Heritability
    (i.e., genetic influence) is indicated when the correlation coefficient for identical twins exceeds that for congenial twins, indicating that shared DNA is an important determinant of personality.
  • Shared environment
    determinants are indicated when the correlation coefficients for identical and fraternal twins are greater than zero and also very similar. These correlations signal that both twins are having experiences in the family that make them alike.
  • Nonshared environment
    is indicated when identical twins do not have similar traits. These influences refer to experiences that are not deemed for either by heritability or by shared ecology factors. Nonshared environmental factors are the experiences that brand individuals within the aforementioned family
    less
    alike. If a parent treats i child more affectionately than some other, and equally a issue this child ends up with higher self-esteem, the parenting in this instance is a nonshared environmental gene.

In the typical twin study, all iii sources of influence are operating simultaneously, and it is possible to make up one’s mind the relative importance of each type.

An
adoption study
compares biologically related people, including twins, who have been reared either separately or apart. Testify for genetic influence on a trait is found when children who have been adopted evidence traits that are more like to those of their biological parents than to those of their adoptive parents. Prove for ecology influence is found when the adoptee is more than like his or her adoptive parents than the biological parents.

The results of family, twin, and adoption studies are combined to get a better thought of the influence of genetics and environment on traits of interest. Tabular array 12.half dozen, “Data from Twin and Adoption Studies on the Heritability of Various Characteristics,” presents information on the correlations and heritability estimates for a variety of traits based on the results of behavioural genetics studies (Bouchard, Lykken, McGue, Segal, & Tellegen, 1990).

Table 12.six Data from Twin and Adoption Studies on the Heritability of Various Characteristics.
[1]
[Skip Table]
Correlation between children raised together Correlation between children raised apart Estimated per centum of full due to
Identical twins Fraternal twins Identical twins Congenial twins Heritability (%) Shared environment (%) Nonshared surroundings (%)
Age of puberty 45 v 50
Aggression 0.43 0.14 0.46 0.06
Alzheimer disease 0.54 0.xvi
Fingerprint patterns 0.96 0.47 0.96 0.47 100
General cerebral ability 56 44
Likelihood of divorce 0.52 0.22
Sexual orientation 0.52 0.22 xviii–39 0–17 61–66
Big Five dimensions xl–50
This table presents some of the observed correlations and heritability estimates for diverse characteristics.

If you look in the 2nd column of Table 12.6 , “Information from Twin and Adoption Studies on the Heritability of Various Characteristics,” yous volition see the observed correlations for the traits between identical twins who accept been raised together in the same house by the same parents. This column represents the pure effects of genetics, in the sense that environmental differences have been controlled to be a minor as possible. You tin can run across that these correlations are higher for some traits than for others. Fingerprint patterns are very highly determined by our genetics (r
= .96), whereas the Big 5 trait dimensions have a heritability of 40% to 50%.

Y’all tin can also encounter from the table that, overall, in that location 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 than similar than fraternal twins who are raised in divide households (column five). These results testify 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 12.6, “Data from Twin and Adoption Studies on the Heritability of Various Characteristics,” that the correlations betwixt identical twins (column 2) and heritability estimates for virtually traits (cavalcade six) are substantially less than 1.00, showing that the environment as well plays an of import role in personality (Turkheimer & Waldron, 2000). For example, for sexual orientation the estimates of heritability vary from xviii% to 39% of the total beyond studies, suggesting that 61% to 82% of the full influence is due to environment.

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You lot might at starting time think that parents would take a strong influence on the personalities of their children, simply this would exist incorrect. As you can run across by looking in column seven of Tabular array 12.half-dozen,” inquiry finds that the influence of shared environment (i.e., the effects of parents or other caretakers) plays niggling or no role in adult personality (Harris, 2006). Shared environment does influence the personality and behaviour of young children, but this influence decreases speedily as the child grows older. Past the time we reach machismo, the impact of shared environment on our personalities is weak at best (Roberts & DelVecchio, 2000). What this ways is that although parents must provide a nourishing and stimulating surround for children, no matter how difficult they try they are not likely to be able to plow their children into geniuses or into professional person athletes, nor will they exist able to turn them into criminals.

If parents are not providing the environmental influences on the child, and so what is? The final column in Table 12.vi,” the influence of nonshared environs, represents any is “left over” later removing the effects of genetics and parents. You lot can run across that these factors — the largely unknown things that happen to the states that brand united states of america different from other people — often have the largest influence on personality.

Studying Personality Using Molecular Genetics

In add-on to the use of behavioural genetics, our understanding of the function of biological science in personality recently has been dramatically increased through the use of
molecular genetics, which is
the study of which genes are associated with which personality traits
(Goldsmith et al., 2003; Strachan & Read, 1999). These advances take occurred equally a effect of new knowledge about the construction of human DNA made possible through the Man Genome Projection and related piece of work that has identified the genes in the homo trunk (Human Genome Project, 2010). Molecular genetics researchers accept besides adult new techniques that allow them to notice the locations of genes within chromosomes and to identify the effects those genes accept when activated or deactivated.

Figure 12.12 Laboratory Mice. These “knockout” mice are participating in studies in which some of their genes accept been deactivated to make up one’s mind the influence of the genes on behaviour.

1 approach that can be used in animals, ordinarily in laboratory mice, is the
knockout study
(every bit shown in Effigy 12.12, “Laboratory Mice”). In this approach the researchers utilise specialized techniques to remove or modify the influence of a gene in a line of
knockout
mice (Crusio, Goldowitz, Holmes, & Wolfer, 2009). The researchers harvest embryonic stem cells from mouse embryos and then alter the Dna of the cells.
The DNA is created so that the activity of sure genes volition be eliminated
or
knocked out. The cells are and then injected into the embryos of other mice that are implanted into the uteruses of living female mice. When these animals are built-in, they are studied to see whether their behaviour differs from a control group of normal animals. Inquiry has found that removing or changing genes in mice can bear upon their anxiety, aggression, learning, and socialization patterns.

In humans, a molecular genetics study ordinarily begins with the drove of a DNA sample from the participants in the written report, usually by taking some cells from the inner surface of the cheek. In the lab, the Dna is extracted from the sampled cells and is combined with a solution containing a mark for the particular genes of interest equally well equally a fluorescent dye. If the gene is nowadays in the DNA of the individual, then the solution will demark to that gene and activate the dye. The more the factor is expressed, the stronger the reaction.

In i mutual approach, DNA is collected from people who have a particular personality characteristic and also from people who practise not. The Deoxyribonucleic acid of the two groups is compared to see which genes differ betwixt them. These studies are at present able to compare thousands of genes at the same time. Enquiry using molecular genetics has constitute genes associated with a diversity of personality traits including novelty-seeking (Ekelund, Lichtermann, Järvelin, & Peltonen, 1999), attention-deficit/hyperactivity disorder (Waldman & Gizer, 2006), and smoking behaviour (Thorgeirsson et al., 2008).

Reviewing the Literature: Is Our Genetics Our Destiny?

Over the past two decades scientists have made substantial progress in understanding the important function of genetics in behaviour. Behavioural genetics studies have found that, for most traits, genetics is more of import than parental influence. And molecular genetics studies have begun to pinpoint the particular genes that are causing these differences. The results of these studies might atomic number 82 you to believe that your destiny is determined by your genes, but this would be a mistaken assumption.

For one, the results of all research must be interpreted advisedly. Over time we volition learn even more nigh the role of genetics, and our conclusions about its influence will likely alter. Current inquiry in the area of behavioural genetics is often criticized for making assumptions about how researchers categorize identical and fraternal twins, virtually whether twins are in fact treated in the same way past their parents, virtually whether twins are representative of children more generally, and about many other issues. Although these critiques may not alter the overall conclusions, it must be kept in mind that these findings are relatively new and will certainly be updated with time (Plomin, 2000).

Furthermore, it is important to reiterate that although genetics is of import, and although we are learning more than every day about its role in many personality variables, genetics does not determine everything. In fact, the major influence on personality is nonshared environmental influences, which include all the things that occur to us that make us unique individuals. These differences include variability in brain construction, diet, education, upbringing, and even interactions among the genes themselves.

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The genetic differences that exist at birth may be either amplified or diminished over time through ecology factors. The brains and bodies of identical twins are not exactly the aforementioned, and they get even more different as they grow upwardly. As a issue, even genetically identical twins have distinct personalities, resulting in big role from environmental effects.

Considering these nonshared environmental differences are nonsystematic and largely accidental or random, it will be difficult to ever determine exactly what will happen to a child equally he or she grows up. Although we do inherit our genes, we do not inherit personality in any fixed sense. The issue of our genes on our behaviour is entirely dependent on the context of our life equally it unfolds day to 24-hour interval. Based on your genes, no one can say what kind of human beingness you will turn out to be or what you will do in life.

Key Takeaways

  • Genes are the basic biological units that transmit characteristics from i generation to the adjacent.
  • Personality is not determined past any unmarried gene, but rather by the actions of many genes working together.
  • Behavioural genetics refers to a diversity of research techniques that scientists use to acquire about the genetic and environmental influences on human behaviour.
  • Behavioural genetics is based on the results of family unit studies, twin studies, and adoptive studies.
  • Overall, genetics has more influence than parents exercise on shaping our personality.
  • Molecular genetics is the study of which genes are associated with which personality traits.
  • The largely unknown environmental influences, known as the nonshared environmental effects, have the largest bear upon on personality. Because these differences are nonsystematic and largely accidental or random, we exercise not inherit our personality in any stock-still sense.

Exercises and Critical Thinking

  1. Think well-nigh the twins you know. Do they seem to be very like to each other, or does it seem that their differences outweigh their similarities?
  2. Describe the implications of the furnishings of genetics on personality, overall. What does it mean to say that genetics “determines” or “does not make up one’s mind” our personality?

References

Baker, C. (2004). Behavioral genetics: An introduction to how genes and environments interact through evolution to shape differences in mood, personality, and intelligence. [PDF] Retrieved from http://www.aaas.org/spp/bgenes/Intro.pdf

Bouchard, T. J., Lykken, D. T., McGue, Yard., Segal, N. L., & Tellegen, A. (1990). Sources of man psychological differences: The Minnesota study of twins reared autonomously.Science, 250(4978), 223–228. Retrieved from http://www.sciencemag.org/cgi/content/abstract/250/4978/223

Crusio, Westward. Eastward., Goldowitz, D., Holmes, A., & Wolfer, D. (2009). Standards for the publication of mouse mutant studies.Genes, Brain & Behavior, 8(1), i–4.

Ekelund, J., Lichtermann, D., Järvelin, M. R., & Peltonen, 50. (1999). Association betwixt novelty seeking and the blazon 4 dopamine receptor factor in a large Finnish accomplice sample.American Periodical of Psychiatry, 156, 1453–1455.

Goldsmith, H., Gernsbacher, M. A., Crabbe, J., Dawson, G., Gottesman, I. I., Hewitt, J.,…Swanson, J. (2003). Research psychologists’ roles in the genetic revolution.American Psychologist, 58(4), 318–319.

Harris, J. R. (2006).No two alike: Human nature and human individuality. New York, NY: Norton.

Human being Genome Project. (2010).
Information. Retrieved from http://world wide web.ornl.gov/sci/techresources/Human_Genome/home.shtml

Långström, N., Rahman, Q., Carlström, E., & Lichtenstein, P. (2010). Genetic and environmental effects on aforementioned-sexual activity sexual behaviour: A population written report of twins in Sweden.Archives of Sexual Behaviour,
39(one), 75-lxxx.

Loehlin, J. C. (1992).Genes and environment in personality development. Thousand Oaks, CA: Sage Publications, Inc.

McGue, Grand., & Lykken, D. T. (1992). Genetic influence on risk of divorce.Psychological Scientific discipline, 3(6), 368–373.

Plomin, R. (2000). Behavioural genetics in the 21st century.International Periodical of Behavioral Development, 24(1), 30–34.

Plomin, R., Fulker, D. W., Corley, R., & DeFries, J. C. (1997). Nature, nurture, and cognitive development from 1 to xvi years: A parent-offspring adoption study.Psychological Science, 8(6), 442–447.

Roberts, B. W., & DelVecchio, W. F. (2000). The rank-order consistency of personality traits from childhood to old age: A quantitative review of longitudinal studies.Psychological Bulletin, 126(1), three–25.

Strachan, T., & Read, A. P. (1999).Human being molecular genetics (2nd ed.). Retrieved from http://world wide web.ncbi.nlm.nih.gov/bookshelf/br.fcgi?volume=hmg&function=A2858

Tellegen, A., Lykken, D. T., Bouchard, T. J., Wilcox, K. J., Segal, Northward. L., & Rich, Southward. (1988). Personality similarity in twins reared autonomously and together.Journal of Personality and Social Psychology, 54(6), 1031–1039.

Thorgeirsson, T. E., Geller, F., Sulem, P., Rafnar, T., Wiste, A., Magnusson, Thousand. P.,…Stefansson, G. (2008). A variant associated with nicotine dependence, lung cancer and peripheral arterial illness.Nature, 452(7187), 638–641.

Tinbergen, North. (1951).The study of instinct (1st ed.). Oxford, England: Clarendon Press.

Turkheimer, E., & Waldron, K. (2000). Nonshared surroundings: A theoretical, methodological, and quantitative review.Psychological Bulletin, 126(1), 78–108.

Waldman, I. D., & Gizer, I. R. (2006). The genetics of attention deficit hyperactivity disorder.Clinical Psychology Review, 26(4), 396–432.

Image Attributions

Figure 12.12:
“Laboratory mice” past Aaron Logan is licensed under CC BY 1.0 license (http://creativecommons.org/licenses/past/1.0/deed.en).


One Genetic Factor That Can Influence Your Personality is __________

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