psy230 chp 8

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Questions and Answers

What is the main reason for the overlap between behavioural genetics and personality psychology?

Both focus on studying genetic variation

Both aim to identify specific genes related to traits

Both disciplines seek to explain human diversity (correct)

Both use DNA samples for measurement

Which approach in behavioural genetics uses DNA samples to measure genetic variation?

Personality psychology approach

Environmental genetics

Molecular genetics (correct)

Classic approach

What distinguishes the classic approach from the modern approach in behavioural genetics?

Study of human diversity

Use of genetic similarity between individuals

Focus on environmental influences

Use of DNA samples for measurement (correct)

What is the primary focus of the classic approach in behavioural genetics?

Inferences about genetic and environmental influences Signup and view all the answers

Which type of studies are still relevant for the study of traits like the Big Five?

Classic studies Signup and view all the answers

What makes it possible to correlate observed differences in participants' genes with their traits in molecular genetics?

Use of DNA samples for measurement Signup and view all the answers

What does the modern approach in behavioural genetics use to measure genetic variation?

DNA samples from a diverse group of individuals Signup and view all the answers

What is the nature versus nurture debate about?

Whether psychological traits are inherited or learned Signup and view all the answers

What does the blank slate model propose?

Humans are born with the same disposition and personality differences are due to socialization Signup and view all the answers

What is the topic of clinical or forensic psychology in relation to inherited dispositions?

Understanding why some people have maladaptive inherited dispositions Signup and view all the answers

What is the focus of research in behavioral genetics?

Genetic and environmental influences on personality Signup and view all the answers

What does the blank slate model not deny about personality?

The existence of personality Signup and view all the answers

What do evolutionary theories suggest about personality traits?

Personality traits are partially inherited Signup and view all the answers

What is the focus of clinical or forensic psychology regarding personality traits?

Understanding maladaptive inherited dispositions Signup and view all the answers

What does a heritability coefficient of 0% indicate?

All of the variation in a phenotype is due to environmental factors Signup and view all the answers

What is the name for the causal effect of genes on the phenotype?

Heritability Signup and view all the answers

What does h2 represent in the context of heritability coefficient?

$h^2$ represents the amount of variance in a phenotype explained by genetic variance Signup and view all the answers

Why is it important to specify the population of a study in behavioral genetics?

Results can vary dramatically from one population to another Signup and view all the answers

What does a heritability coefficient of 100% indicate?

All of the variation in a phenotype is due to genetic variation Signup and view all the answers

What reflects the influence of genes that are inherited from parents?

$h^2$ Signup and view all the answers

What does '1-$h^2$' represent in the context of heritability coefficient?

The amount of variance in a phenotype explained by environmental variance Signup and view all the answers

Why do heritability coefficients depend on the population in which they are estimated?

Results can vary dramatically from one population to another Signup and view all the answers

What does 'h' reflect in terms of genetic influence?

The causal effect of genes on the phenotype Signup and view all the answers

What does '1-h' represent in relation to genetic and environmental influences?

The amount of variance in a phenotype explained by environmental factors Signup and view all the answers

Why might some people believe that heritability coefficients are meaningless?

Due to their dependence on the population being studied Signup and view all the answers

What is the term used by personality psychologists to refer to specific observable attributes?

Traits Signup and view all the answers

What do behavioural geneticists call specific observable attributes?

Phenotypes Signup and view all the answers

What is the information encoded in an individual's DNA known as?

Genotype Signup and view all the answers

What are variations in the genome that can produce differences in humans' phenotypes called?

Allels Signup and view all the answers

What do genes come in different versions known as?

Allels Signup and view all the answers

What is the focus of environmental factors in behavioural genetics?

On environment factors that vary across individuals Signup and view all the answers

What does the classic approach in behavioural genetics not measure directly?

The unobserved genetic variation Signup and view all the answers

What can sometimes be responsible for a phenotype?

A single variation of a gene Signup and view all the answers

What are variations in many genes that contribute to variation in a phenotype called?

Polygenic Signup and view all the answers

What does the heritability coefficient measure?

The proportion of individual differences in a trait that can be attributed to genetic differences Signup and view all the answers

What does the classic twin design aim to separate the influence of?

Genes and shared environment Signup and view all the answers

How is the heritability coefficient computed using twin correlations?

$h^2 = r_{MZ} - r_{DZ}$ Signup and view all the answers

What does a correlation of $r = .87$ for height in MZ twins suggest?

$87%$ heritability of height Signup and view all the answers

What is a key limitation of twin studies mentioned in the text?

Rarity of twins and adoptions, and inability to replicate results Signup and view all the answers

What does the causal model in Figure 8.2 explain?

The observed correlation between twins' phenotypes Signup and view all the answers

What does a correlation of $r = .48$ for personality traits in MZ twins suggest?

50% heritability of personality traits Signup and view all the answers

What does 'no assortative mating' mean in the context of twin studies?

Parents do not select mates based on similar traits or characteristics Signup and view all the answers

What does 'equal shared environments for MZ and DZ twins' mean in the classic twin design?

Both types of twins experience identical environments during development Signup and view all the answers

What reflects the difference in genetic similarity between MZ and DZ twins?

The difference in their correlation for a specific trait Signup and view all the answers

What percentage of height heritability is estimated from the given information?

90% Signup and view all the answers

What does the estimate of 3% due to shared environmental factors indicate?

Shared environmental factors have a small effect on height variation Signup and view all the answers

What does the estimate of 7% due to non-shared environmental factors show?

Non-shared environmental factors are more likely to make twins dissimilar than similar Signup and view all the answers

What does the relatively small variance in access to protein-rich foods in North America imply?

Nutrition can only make a small difference to variation in height in North America Signup and view all the answers

What is the total variance in height separated into, based on the given information?

Genetic factors, shared environmental factors, and non-shared environmental factors Signup and view all the answers

What do the estimates derived from MZ twins growing up apart and the given calculations suggest about the influence of shared environment on height?

Shared environment has a small effect on height variation Signup and view all the answers

What do the estimates obtained from MZ twins growing up apart and the given calculations indicate about the influence of non-shared environment on making twins dissimilar?

Non-shared environment is more likely to make twins dissimilar than similar Signup and view all the answers

What do the given estimates suggest about the impact of nutrition on height variation?

Nutrition can only make a small difference to variation in height Signup and view all the answers

How are genetic, shared environmental, and non-shared environmental factors contributing to the total variance in height?

Genetic factors contribute 90%, shared environmental contributes 3%, and non-shared environmental contributes 7% Signup and view all the answers

What is the genetic similarity between dizygotic twins (DZ)?

50% Signup and view all the answers

Why are dizygotic twins (DZ) more similar to monozygotic twins (MZ) than normal siblings?

Because they have more similar environmental conditions Signup and view all the answers

What is the main reason for comparing monozygotic (MZ) twins to dizygotic (DZ) twins rather than to siblings?

To control for environmental factors Signup and view all the answers

What is the biggest challenge in twin studies?

Recruiting a large number of participants Signup and view all the answers

Why are dizygotic twins (DZ) genetically not different from normal siblings?

$h^2$ value is the same for DZ and normal siblings Signup and view all the answers

What percentage of genes do children inherit from each parent?

50% Signup and view all the answers

What is the result of a split of the same fertilized egg during the early stages of development of a fetus?

Monozygotic twins (MZ) Signup and view all the answers

What do dizygotic twins (DZ) result from?

Two eggs in the uterus fertilized by two different sperms Signup and view all the answers

What makes it possible for behavioural geneticists to compare MZ and DZ twins?

Their shared environment during upbringing Signup and view all the answers

Why are monozygotic (MZ) twins genetically identical?

They share 100% of their genes Signup and view all the answers

What percentage of the variance in handedness is inherited?

25% Signup and view all the answers

What term would be more appropriate instead of 'unshared environment' in twins?

Unexplained variance Signup and view all the answers

What does the finding about married MZ twins' happiness suggest?

Marriage is an unshared environmental factor Signup and view all the answers

What do the results of the study comparing life-satisfaction in MZ twin pairs demonstrate?

Current life circumstances can influence environmental factors Signup and view all the answers

What does the text suggest about the influence of environmental factors on handedness?

'Unshared environment' could reflect unique biological processes or measurement error Signup and view all the answers

What is the likely cause of left-handedness according to the text?

Different lateralization of the brain Signup and view all the answers

What type of environmental factors can influence adult twins' differences?

Current life circumstances Signup and view all the answers

What does the text suggest about the term 'unshared environment' when studying traits in twins?

It could reflect unique biological processes or measurement error. Signup and view all the answers

What does the study comparing life-satisfaction in MZ twin pairs illustrate about environmental influences?

Environmental influences can be due to current life circumstances rather than parenting. Signup and view all the answers

What does the text imply about the causes of left-handedness?

Different lateralization of the brain can lead to left-handedness. Signup and view all the answers

What did a rare adoption study of personality traits related to the Big Five find?

The shared environment may contribute to adolescents' personalities. Signup and view all the answers

What did the adoption study find about the shared environment effect on personality traits?

The strongest shared environment effect was found for a scale called 'Traditionalism.' Signup and view all the answers

What do results from the adoption study suggest about the variance in personality traits?

Genes explain 40% of the variance in personality traits, while the shared environment explains 20%. Signup and view all the answers

What did studies using a multi-method approach find about unshared environmental variance in twin studies?

Some of the unshared environmental variance in twin studies could be measurement error, leading to increased heritability estimates. Signup and view all the answers

What is an example of unshared biological development mentioned in the text?

'Handedness,' which is not actively influenced by parents. Signup and view all the answers

'Handedness' could be influenced by recessive genes, similar to which other trait?

'Eye color,' where two brown-eyed parents carrying a blue-eye allele could have a blue-eyed child with a 25% chance. Signup and view all the answers

What do unshared environmental factors in twin studies primarily represent?

Unidentifiable factors that could be random processes occurring during human development. Signup and view all the answers

What does understanding the influence of shared and unshared environment on personality traits require?

More evidence from adoption studies and a multi-method approach to measurement. Signup and view all the answers

What does the development of a human adult from an embryo to an adult lead to?

Differences in individuals despite starting with the same DNA. Signup and view all the answers

What does measurement error in classic twin studies tend to do?

Underestimate the similarity of twins' personalities and underestimate heritability. Signup and view all the answers

What does the pattern of MZ and DZ twin correlations suggest about the heritability of personality?

Half of the personality variance is due to genes and the other half is due to unshared environmental factors Signup and view all the answers

What does the lack of shared environmental factors influencing personality mean for parental influence?

Parental influence makes twins dissimilar rather than similar Signup and view all the answers

Why might some parents find it surprising that their parenting styles do not produce similar outcomes in their children's personalities?

They expect their children to have similar personalities due to similar parenting styles Signup and view all the answers

What was particularly unwelcome among developmental psychologists regarding the influence of parenting styles on child development?

The finding that similar parenting styles do not produce similar outcomes Signup and view all the answers

What do many parents believe about shaping their children's personality, especially with their first child?

They believe they can shape their children's personality significantly Signup and view all the answers

What did the lack of shared environmental factors influencing personality mean for the shared environment?

It has a minimal impact on shaping personality Signup and view all the answers

Why might some parents learn from experience that their influence is rather limited when they have a second child?

Because they observe differences in personalities despite using the same parenting styles for both siblings Signup and view all the answers

What is the primary reason for MZ twins correlations to exceed two times the DZ correlations?

Genetic and non-additive genetic influences Signup and view all the answers

Why does the standard formula for heritability estimation not work for phenotypes like eye color?

Limitations on explained variance Signup and view all the answers

What do DZ correlations less than half of MZ correlations suggest about personality traits?

Additive and non-additive genetic influences Signup and view all the answers

Why are shared environment effects on personality considered minimal?

Similarity of MZ twins who grew up together and apart Signup and view all the answers

What does the decreasing influence of shared environment over time imply?

Decreasing similarity among twins or siblings in religiosity Signup and view all the answers

What is the consensus about the percentage of personality trait variance caused by genetic differences?

Around 50% Signup and view all the answers

What do adoption studies and studies of children with different biological parents in the same household provide rare insights into?

Personality research Signup and view all the answers

What reflects parents' early influence on personality but does not last into adulthood?

Decreasing MZ and DZ correlations with age Signup and view all the answers

What phenotypes do parents have a lasting influence on into early adulthood, indicating the impact of shared environment?

Religiosity Signup and view all the answers

What does behavior genetics research emphasize about parenting's role in children's personalities?

Providing a supportive environment for children's unique personalities. Signup and view all the answers

What does an additive model in genetics assume?

Phenotype is simply the sum of variants that influence a trait Signup and view all the answers

What does the example of eye color inheritance illustrate?

Phenotype is the result of complex gene interaction effects Signup and view all the answers

What does 'gene by gene interaction' refer to?

Interaction between multiple genes influencing a trait Signup and view all the answers

What is the problem with the simple additive model in genetics?

It may not accurately represent how genes influence phenotypes Signup and view all the answers

In the context of genetics, what does 'non-additive effects' refer to?

$h^2$ representing non-additive genetic interactions Signup and view all the answers

What is the primary difference between gene-environment correlations and personality-situation correlations?

Gene-environment correlations focus on traits or phenotypes, while personality-situation correlations explain specific behaviors. Signup and view all the answers

What does the '10,000 hours to gain expertise' idea suggest about skill development?

Most people will get pretty good at something they practice for 10,000 hours. Signup and view all the answers

What does the case of the Williams sisters illustrate about skill development?

Practice combined with genetic predisposition contributes to expertise in a particular skill. Signup and view all the answers

What does the concept of gene-environment correlations imply about the influence of genetic dispositions on individual interests?

Individual interests may have a genetic basis. Signup and view all the answers

What does the 10,000 hours rule fail to account for in terms of skill development?

The role of genetic predisposition in skill development. Signup and view all the answers

What does the case of the author's guitar and Badminton experiences suggest about gene-environment correlations?

$r = .87$ correlation for height in MZ twins suggests that individuals' genetic dispositions may influence their interests. Signup and view all the answers

What does the case of the author's guitar and Badminton experiences suggest about the influence of environmental factors on individual interests?

The environment may shape individual interests. Signup and view all the answers

What was the best-known demonstration of the impact of inherited diseases according to the text?

Phenylketonuria (PKU) Signup and view all the answers

What is a common misunderstanding about genetic factors in behavioral genetics, as mentioned in the text?

The focus on genetic factors supports fascist and eugenic ideologies Signup and view all the answers

What did the finding that sexual orientation is partially inherited lead to, as mentioned in the text?

An argument for gay and lesbian rights Signup and view all the answers

What did the use of heritability as a progressive argument for gay and lesbian rights demonstrate, according to the text?

Findings in behavioral genetics are independent of political and social implications Signup and view all the answers

What was a problem with evidence of inherited dispositions when homosexuality was viewed as a disorder?

$h^2$ implies that some people were born with a disease Signup and view all the answers

What do individuals who believe that sexual orientation is innate tend to support, according to the text?

Gay and lesbian rights Signup and view all the answers

What does the text imply about politics and values in arguments about heritability?

They are only involved when values are assigned to certain traits. Signup and view all the answers

What was a relevant outcome of discovering Phenylketonuria (PKU), according to the text?

Avoiding negative consequences with a special diet. Signup and view all the answers

What does the text suggest about using heritability as an argument for societal change?

It became an argument for societal change when certain traits were viewed as normal variation. Signup and view all the answers

What is a common misconception about heritability coefficients?

High heritability coefficients imply fixed traits, when in fact they reflect low variability in environmental factors. Signup and view all the answers

What does the study of adolescent twins' musical abilities show about gene-environment correlations?

It shows gene-environment correlations, with practice time as the environmental variable. Signup and view all the answers

What does the text suggest about the impact of genes and environment on musical abilities?

Genetic factors explain 20% of the variance in musical abilities, slightly stronger than the effect of practice. Signup and view all the answers

What is crucial for understanding skills and abilities according to the text?

Gene-environment correlations, emphasizing the impact of opportunity and practice. Signup and view all the answers

How can environmental effects be demonstrated for traits with high heritability?

By comparing different generations and observing changes in mean differences between generations. Signup and view all the answers

What did lifestyle changes demonstrate about environmental factors and heritability coefficients?

They produced notable increases in average Body-Mass-Index, demonstrating that environmental factors can influence traits despite high heritability coefficients. Signup and view all the answers

What did the review article from 2021 show about the variance genetic profiles could explain in a large number of phenotypes/characteristics?

The largest effect was found for childhood IQ scores (~ 25% of the variance) Signup and view all the answers

What did the genetic profiles explain about personality traits like extraversion and neuroticism?

Genetic profiles explained about 10% of the variance in both extraversion and neuroticism Signup and view all the answers

What did the text reveal about the effect size for drug use?

The effect size for drug use was between around 10+/- 5% Signup and view all the answers

What did the molecular genetics studies reveal about genes contributing to human diversity?

Molecular genetics provides direct evidence that genes contribute to human diversity Signup and view all the answers

What did the second finding indicate about molecular genetics studies and twin studies?

'So far this approach explains only a portion of the variance that twin studies attribute to genes' Signup and view all the answers

What did the text suggest about finding genetic predictors of important personality traits and life outcomes?

Extremely large samples are needed to find genetic profiles that are replicable across studies. Signup and view all the answers

What did the text reveal about genetic profiles' ability to explain characteristics like happiness/life satisfaction, age of first intercourse, and number of children?

The smallest effect was found for happiness/life-satisfaction, age of first intercourse, and number of children (< 5%) Signup and view all the answers

What did a review article from 2021 demonstrate about genetic predictors' ability to explain homosexuality?

Genetic profile explained less than 10% of the variance in homosexuality Signup and view all the answers

Study Notes

Twin Studies and Heritability

Behavioral geneticists use twin studies to separate genetic and environmental influences on traits.
Adoption studies with MZ twins show that the correlation between phenotypes can be interpreted as the heritability coefficient.
The causal model in Figure 8.2 explains the observed correlation between twins' phenotypes.
A study of MZ twins who grew up apart showed a correlation of r =.87 for height, suggesting 87% heritability.
The same study found an average correlation of r =.5 for personality traits, suggesting 50% heritability.
A key limitation of the study is the rarity of twins and adoptions, and the inability to replicate results.
The classic twin design compares the similarity between MZ and DZ twins raised together.
The design aims to separate the influence of genes and shared environment, assuming equal shared environments for MZ and DZ twins.
Assumptions include no assortative mating and that genetic similarity of DZ twins is half of MZ twins.
The classic twin design uses a causal model to estimate heritability and shared environment influence.
A study found a correlation of r =.93 for MZ twins’ height and r =.48 for DZ twins’ height, illustrating the classic twin design.
The heritability coefficient can be computed by subtracting the DZ correlation from the MZ correlation.

Influence of Parents on Children's Personality Traits

Parents may try to influence their children's personality traits, such as politeness, hard work, and outgoing nature, but this influence may be limited.
Adoption studies, which avoid genetic similarity between parents and children, are essential for understanding the influence of shared environment on personality traits.
A rare adoption study of personality traits related to the Big Five found that the shared environment may contribute to adolescents' personalities.
The strongest shared environment effect in the adoption study was found for a scale called "Traditionalism," linked to the Liberalism facet of Openness to Experience.
Results from the adoption study suggest that genes explain 40% of the variance in personality traits, while the shared environment explains 20%.
Measurement error in classic twin studies may underestimate the similarity of twins' personalities and underestimate heritability.
Studies using a multi-method approach found that some of the unshared environmental variance in twin studies could be measurement error, leading to increased heritability estimates.
Unshared environmental factors in twin studies may not be identifiable and could be random processes that occur during human development.
The development of a human adult from an embryo to an adult is complex, leading to differences in individuals despite starting with the same DNA.
Handedness is an example of unshared biological development, with about 10% of the population being left-handed, which is not actively influenced by parents.
Handedness could be influenced by recessive genes, similar to eye color, where two brown-eyed parents carrying a blue-eye allele could have a blue-eyed child with a 25% chance.
Understanding the influence of shared and unshared environment on personality traits requires more evidence from adoption studies and a multi-method approach to measurement.

Genetic and Environmental Influences on Personality

DZ twins are less similar in phenotypes due to dominant-recessive and interaction effects, while MZ twins have identical genes and inherit the same interaction effects.
MZ twins correlations can exceed two times the DZ correlations due to the impact of genetic and non-additive genetic influences.
The standard formula for heritability estimation does not work for phenotypes like eye color due to limitations on explained variance.
Some personality traits show DZ correlations less than half of MZ correlations, suggesting both additive and non-additive genetic influences.
The consensus is that around 50% of personality trait variance is caused by genetic differences, with the remaining variance reflecting random factors.
Shared environment effects on personality are minimal, as evidenced by the similarity of MZ twins who grew up together and apart.
Adoption studies and studies of children with different biological parents in the same household are rare in the context of personality research.
Parental influences on behavior are distinct from influences on personality, and parents can still influence behavior even when children are independent.
Parents have an early influence on personality, but this influence does not last into adulthood, as seen in decreasing MZ and DZ correlations with age.
Parents have a lasting influence on some phenotypes, such as religiosity, into early adulthood, indicating the impact of shared environment.
The decreasing influence of shared environment over time implies decreasing similarity among twins or siblings in religiosity.
Behavior genetics research changes the perception of parenting by emphasizing the role of parents in providing a supportive environment for children's unique personalities.

Expertise, Gene-Environment Correlations, and Misconceptions about Heritability

The 10,000-hour rule for expertise suggests that passion and motivation to invest time in an activity are crucial to achieving expertise.
Personal experience in academic psychology highlights the importance of passion and investment of time in developing expertise.
Success in life often stems from finding and pursuing one's passion, allowing individuals to overcome obstacles and invest time in their chosen field.
Environmental predictors for personality traits like the Big Five are not reliable, making it challenging to study gene-environment correlations for personality traits.
A study of adolescent twins' musical abilities shows gene-environment correlations, with practice time as the environmental variable.
Genetic variance accounts for 37% of the variance in practice times, and shared environment explains 44% of the variance, indicating the influence of both genes and environment.
Practice times moderately affect musical abilities, with genetic factors explaining 20% of the variance, slightly stronger than the effect of practice.
Shared environmental factors, including parental influences, play a significant role in influencing practice times and abilities.
Gene-environment correlations are crucial for understanding skills and abilities, emphasizing the impact of opportunity and practice.
Misconceptions about heritability include the belief that high heritability coefficients imply fixed traits, when in fact they reflect low variability in environmental factors.
Environmental effects can be demonstrated for traits with high heritability by comparing different generations and observing changes in mean differences between generations.
While individual variation in each generation is substantially heritable, lifestyle changes have produced notable increases in average Body-Mass-Index, demonstrating that environmental factors can influence traits despite high heritability coefficients.

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Test your knowledge about the nature versus nurture debate, exploring the inheritance of physical and psychological traits in animals and humans. Delve into evolutionary theories and the concept of the blank slate model.