How Would You Know if Personality Runs in Our Genes Quiz

Chapter four. Genetics and Development

4.iv Is Personality More Nature or More Nurture? Behavioural and Molecular Genetics

Charles Stangor and Jennifer Walinga

Learning Objectives

1. Explicate how genes transmit personality from 1 generation to the side by side.
2. Outline the methods of behavioural genetics studies and the conclusions that we can draw from them most the determinants of personality.
3. Explain how molecular genetics research helps u.s.a. understand the role of genetics in personality.

One question that is exceedingly important for the study of personality concerns the extent to which it is the result of nature or nurture. If nature is more important, then our personalities volition form early on in our lives and volition be difficult to change later. If nurture is more important, notwithstanding, so our experiences are likely to exist particularly important, and we may be able to flexibly change our personalities over fourth dimension. In this section nosotros will see that the personality traits of humans and animals are adamant in big part by their genetic makeup, and thus information technology is no surprise that identical twins Paula Bernstein and Elyse Schein turned out to exist very like even though they had been raised separately. But we will also run across that genetics does not decide everything.

In the nucleus of each cell in your body are 23 pairs of chromosomes. I of each pair comes from your father, and the other comes from your female parent. The chromosomes are fabricated up of strands of the molecule DNA (dna), and the Deoxyribonucleic acid is grouped into segments known every bit genes. A gene is the bones biological unit that transmits characteristics from one generation to the next. Human cells have about 25,000 genes.

The genes of different members of the same species are almost identical. The Dna in your genes, for example, is almost 99.ix% the same as the Deoxyribonucleic acid in my genes and in the DNA of every other human being. These common genetic structures lead members of the same species to be born with a diverseness of behaviours that come naturally to them and that ascertain the characteristics of the species. These abilities and characteristics are known as instincts—circuitous inborn patterns of behaviours that help ensure survival and reproduction (Tinbergen, 1951). Dissimilar animals have different instincts. Birds naturally build nests, dogs are naturally loyal to their human caretakers, and humans instinctively larn to walk and to speak and understand language.

But the strength of unlike 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 ameliorate than others do. These differences are adamant in part by the modest amount (in humans, the 0.1%) of the differences in genes among the members of the species.

Personality is not adamant by any single gene, but rather past the deportment of many genes working together. There is no "IQ gene" that determines intelligence and there is no "good marriage-partner factor" that makes a person a specially adept matrimony bet. Furthermore, even working together, genes are not so powerful that they tin can control or create our personality. Some genes tend to increase a given feature and others work to subtract that same characteristic — the complex relationship amidst the various genes, as well as a variety of random factors, produces the final outcome. Furthermore, genetic factors always piece of work with environmental factors to create personality. Having a given pattern of genes doesn't necessarily hateful that a particular trait volition develop, because some traits might occur only in some environments. For example, a person may accept a genetic variant that is known to increase his or her chance for developing emphysema from smoking. But if that person never smokes, and then emphysema well-nigh probable will non develop.

Studying Personality Using Behavioural Genetics

Perhaps the most direct fashion to study the function of genetics in personality is to selectively breed animals for the trait of involvement. In this arroyo 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 nosotros can assume that the trait has genetic origins. In this style, scientists take studied the office 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 convenance studies can be informative, they are clearly non useful for studying humans. For this psychologists rely on behavioural genetics—a diverseness of enquiry techniques that scientists utilize to learn about the genetic and environmental influences on homo behaviour by comparing the traits of biologically and nonbiologically related family unit members (Baker, 2004). Behavioural genetics is based on the results of family studies, twin studies, and adoptive studies.

A family unit studystarts with ane person who has a trait of interest — for instance, a developmental disorder such as autism — and examines the private'south family tree to determine the extent to which other members of the family also take the trait. The presence of the trait in showtime-caste 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 afar family members. The scientists then analyze the patterns of the trait in the family members to run into the extent to which it is shared by closer and more distant relatives.

Although family studies tin 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 essentially the aforementioned ready of genes, while fraternal (or dizygotic) twins have, on average, a one-half-identical set. The idea is that if the twins are raised in the same household, then the twins will exist influenced by their environments to an equal caste, and this influence will exist pretty much equal for identical and fraternal twins. In other words, if environmental factors are the aforementioned, and then the merely factor that can make identical twins more like than fraternal twins is their greater genetic similarity.

In a twin report, the data from many pairs of twins are nerveless and the rates of similarity for identical and congenial pairs are compared. A correlation coefficient is calculated that assesses the extent to which the trait for ane 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 fraternal twins, indicating that shared DNA is an important determinant of personality.
• Shared environment determinants are indicated when the correlation coefficients for identical and congenial twins are greater than zero and also very similar. These correlations indicate that both twins are having experiences in the family unit that make them alike.
• Nonshared environment is indicated when identical twins do non have like traits. These influences refer to experiences that are not accounted for either by heritability or by shared environmental factors. Nonshared environmental factors are the experiences that make individuals within the same family less alike. If a parent treats one kid more than affectionately than another, and every bit a outcome this child ends upwardly with college self-esteem, the parenting in this case is a nonshared ecology factor.

In the typical twin report, all three sources of influence are operating simultaneously, and it is possible to determine the relative importance of each type.

An adoption reportcompares biologically related people, including twins, who have been reared either separately or autonomously. Evidence for genetic influence on a trait is constitute when children who have been adopted show traits that are more than 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 become a amend idea of the influence of genetics and surroundings on traits of involvement. Tabular array iv.1, "Information from Twin and Adoption Studies on the Heritability of Various Characteristics," presents data 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 four.1 Data from Twin and Adoption Studies on the Heritability of Various Characteristics.
	Correlation between children raised together		Correlation between children raised apart		Estimated percent of total due to
	Identical twins	Congenial twins	Identical twins	Fraternal twins	Heritability (%)	Shared environment (%)	Nonshared surroundings (%)
Age of puberty					45	five	50
Aggression	0.43	0.14	0.46	0.06
Alzheimer affliction	0.54	0.xvi
Fingerprint patterns	0.96	0.47	0.96	0.47	100	0	0
General cerebral power					56	0	44
Likelihood of divorce	0.52	0.22
Sexual orientation	0.52	0.22			eighteen–39	0–17	61–66
Big Five dimensions					40–50
This tabular array presents some of the observed correlations and heritability estimates for various characteristics. Sources: Långström, et al, 2010; Loehlin, 1992; McGue & Lykken, 1992; Plomin et al, 1997; Tellegen et al, 1988.

If you look in the second column of Table four.1 , "Information from Twin and Adoption Studies on the Heritability of Diverse Characteristics," you volition encounter the observed correlations for the traits betwixt identical twins who take been raised together in the same house past the same parents. This column represents the pure effects of genetics, in the sense that ecology differences have been controlled to exist a small-scale as possible. You can run into that these correlations are higher for some traits than for others. Fingerprint patterns are very highly determined past our genetics (r = .96), whereas the Large Five trait dimensions take a heritability of xl% to 50%.

You can likewise see from the table that, overall, at that place is more than influence of nature than of parents. Identical twins, even when they are raised in separate households by unlike parents (column 4), turn out to be quite similar in personality, and are more similar than fraternal twins who are raised in separate households (cavalcade five). These results show that genetics has a stiff influence on personality, and helps explain why Elyse and Paula were so similar when they finally met.

Despite the overall part of genetics, you can see in Table 4.1, "Data from Twin and Adoption Studies on the Heritability of Various Characteristics," that the correlations between identical twins (column 2) and heritability estimates for almost traits (column 6) are substantially less than ane.00, showing that the environment likewise plays an important role in personality (Turkheimer & Waldron, 2000). For instance, for sexual orientation the estimates of heritability vary from xviii% to 39% of the total beyond studies, suggesting that 61% to 82% of the total influence is due to environment.

Yous might at outset retrieve that parents would have a potent influence on the personalities of their children, simply this would be incorrect. As y'all can run across by looking in cavalcade 7 of Table 4.ane," research finds that the influence of shared environs (i.e., the furnishings of parents or other caretakers) plays little or no office in adult personality (Harris, 2006). Shared environment does influence the personality and behaviour of immature children, simply this influence decreases rapidly as the child grows older. By the time we achieve adulthood, the impact of shared surround on our personalities is weak at all-time (Roberts & DelVecchio, 2000). What this means is that although parents must provide a nourishing and stimulating surround for children, no matter how hard they endeavour they are not likely to exist able to plow their children into geniuses or into professional athletes, nor volition 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 four.one," the influence of nonshared environment, represents whatsoever is "left over" subsequently removing the effects of genetics and parents. You can encounter that these factors — the largely unknown things that happen to us that make us dissimilar from other people — often have the largest influence on personality.

Studying Personality Using Molecular Genetics

In addition to the use of behavioural genetics, our understanding of the role of biological science in personality recently has been dramatically increased through the utilise 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 have occurred every bit a result of new knowledge almost the structure of human Dna made possible through the Human Genome Project and related work that has identified the genes in the human body (Homo Genome Project, 2010). Molecular genetics researchers have also developed new techniques that allow them to observe the locations of genes within chromosomes and to identify the effects those genes have when activated or deactivated.

Figure 4.xviii Laboratory Mice. These "knockout" mice are participating in studies in which some of their genes have been deactivated to determine the influence of the genes on behaviour.

One approach that can be used in animals, usually in laboratory mice, is the knockout report (every bit shown in Figure four.18, "Laboratory Mice"). In this approach the researchers use 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 and then that the activeness of sure genes volition be eliminated or knocked out. The cells are 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 command group of normal animals. Research has found that removing or changing genes in mice can affect their anxiety, aggression, learning, and socialization patterns.

In humans, a molecular genetics written report normally begins with the drove of a DNA sample from the participants in the study, usually past 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 marker for the particular genes of interest as well as a fluorescent dye. If the factor is nowadays in the Deoxyribonucleic acid of the individual, then the solution volition bind to that factor and actuate the dye. The more the gene is expressed, the stronger the reaction.

In one mutual approach, DNA is collected from people who have a detail personality characteristic and also from people who practise not. The Deoxyribonucleic acid of the two groups is compared to come across which genes differ between them. These studies are now able to compare thousands of genes at the same time. Research using molecular genetics has establish genes associated with a variety 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 role of genetics in behaviour. Behavioural genetics studies have found that, for most traits, genetics is more than 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 adamant by your genes, only this would be a mistaken assumption.

For one, the results of all research must exist interpreted advisedly. Over time we will acquire even more than about the office of genetics, and our conclusions about its influence will likely change. Current inquiry in the area of behavioural genetics is frequently criticized for making assumptions about how researchers categorize identical and congenial twins, well-nigh whether twins are in fact treated in the same style by their parents, about whether twins are representative of children more generally, and about many other issues. Although these critiques may not change the overall conclusions, information technology must be kept in mind that these findings are relatively new and will certainly be updated with time (Plomin, 2000).

Furthermore, information technology is important to reiterate that although genetics is of import, and although we are learning more every day about its office in many personality variables, genetics does non 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 structure, nutrition, educational activity, upbringing, and even interactions among the genes themselves.

The genetic differences that be at birth may be either amplified or diminished over time through environmental factors. The brains and bodies of identical twins are non exactly the same, and they become even more different as they grow upwardly. Every bit a event, even genetically identical twins accept singled-out personalities, resulting in large function from ecology furnishings.

Because 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 as he or she grows upward. Although we do inherit our genes, we do not inherit personality in any fixed sense. The outcome of our genes on our behaviour is entirely dependent on the context of our life as information technology unfolds solar day to day. Based on your genes, no one tin can say what kind of man being you will turn out to be or what y'all will do in life.

Key Takeaways

• Genes are the basic biological units that transmit characteristics from one generation to the next.
• Personality is not adamant by any single gene, but rather by the actions of many genes working together.
• Behavioural genetics refers to a variety of enquiry techniques that scientists utilize to learn 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 practise 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, take the largest affect on personality. Because these differences are nonsystematic and largely accidental or random, we do not inherit our personality in whatsoever fixed sense.

Exercises and Critical Thinking

1. Think about 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 information technology mean to say that genetics "determines" or "does not determine" our personality?

---

Prototype Attributions

Figure iv.xviii: "Laboratory mice" by Aaron Logan is licensed under CC Past 1.0 license (http://creativecommons.org/licenses/by/one.0/deed.en).

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, Grand., Segal, N. L., & Tellegen, A. (1990). Sources of human 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, W. E., Goldowitz, D., Holmes, A., & Wolfer, D. (2009). Standards for the publication of mouse mutant studies.Genes, Brain & Behavior, 8(1), 1–4.

Ekelund, J., Lichtermann, D., Järvelin, G. R., & Peltonen, L. (1999). Association between novelty seeking and the type 4 dopamine receptor cistron in a large Finnish cohort sample.American Journal of Psychiatry, 156, 1453–1455.

Goldsmith, H., Gernsbacher, Yard. A., Crabbe, J., Dawson, Grand., Gottesman, I. I., Hewitt, J.,…Swanson, J. (2003). Research psychologists' roles in the genetic revolution.American Psychologist, 58(iv), 318–319.

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

Human Genome Projection. (2010). Information. Retrieved from http://world wide web.ornl.gov/sci/techresources/Human_Genome/dwelling house.shtml

Långström, N., Rahman, Q., Carlström, E., & Lichtenstein, P. (2010). Genetic and environmental furnishings on same-sex sexual behaviour: A population study of twins in Sweden.Athenaeum of Sexual Behaviour, 39(1), 75-80.

Loehlin, J. C. (1992).Genes and environs in personality development. 1000 Oaks, CA: Sage Publications, Inc.

McGue, Grand., & Lykken, D. T. (1992). Genetic influence on take chances of divorce.Psychological Science, 3(6), 368–373.

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

Plomin, R., Fulker, D. W., Corley, R., & DeFries, J. C. (1997). Nature, nurture, and cognitive development from 1 to sixteen years: A parent-offspring adoption study.Psychological Scientific discipline, 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 molecular genetics (2nd ed.). Retrieved from http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=hmg&part=A2858

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

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

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

Turkheimer, E., & Waldron, Thou. (2000). Nonshared environment: 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.

hallfately80.blogspot.com

Source: https://openpress.usask.ca/introductiontopsychology/chapter/is-personality-more-nature-or-more-nurture-behavioral-and-molecular-genetics/

Share this post