nature, nurture and human diversity chapter 4. nature vs. nurture psychology’s biggest question...

Nature, Nurture and Nature, Nurture and Human DiversityHuman Diversity

Chapter 4Chapter 4

Nature Vs. NurtureNature Vs. Nurture

Psychology’s Biggest QuestionPsychology’s Biggest Question Regardless of upbringing, ethnicity or Regardless of upbringing, ethnicity or

gender, all human beings tend to gender, all human beings tend to – Develop in infancy and toddlerhood in the Develop in infancy and toddlerhood in the

same order (roll over, sit up, crawl, walk)same order (roll over, sit up, crawl, walk)– Are drawn to people with similar interests.Are drawn to people with similar interests.– Laugh when happyLaugh when happy– Grieve death or loss of a loved oneGrieve death or loss of a loved one

How does Genetics influence How does Genetics influence Behavior?Behavior?

Each individual is comprised of genes Each individual is comprised of genes that are inherited equally from our that are inherited equally from our mother and father. mother and father.

This unique combination ultimately is This unique combination ultimately is what makes us different from every what makes us different from every other human being.other human being.

Behavioral geneticistsBehavioral geneticists study our study our differences and weigh the effects and differences and weigh the effects and interplay of heredity and interplay of heredity and environment.environment.

Studying TwinsStudying Twins

The most ethical way to study the The most ethical way to study the nature-nurture debate is through the nature-nurture debate is through the study of twins.study of twins.– Identical TwinsIdentical Twins come from the same come from the same

fertilized egg and therefore are genetically fertilized egg and therefore are genetically identical.identical.

– Fraternal TwinsFraternal Twins are siblings who developed are siblings who developed from separate fertilized eggs. While they from separate fertilized eggs. While they shared the same fetal environment, they are shared the same fetal environment, they are no closer genetically than any other siblings.no closer genetically than any other siblings.

Studying TwinsStudying Twins

Identical Twins can be slightly Identical Twins can be slightly different in the following ways:different in the following ways:– While they have the same genes, they While they have the same genes, they

don’t always have the same number of don’t always have the same number of copies of those genes, which may copies of those genes, which may explain why one twin is at greater risk explain why one twin is at greater risk for disease than the other.for disease than the other.

– If twins don’t share the same placenta If twins don’t share the same placenta (1 in 3), environment may provide (1 in 3), environment may provide better nourishment to one placenta and better nourishment to one placenta and can contribute to differences.can contribute to differences.

Genetics and TwinsGenetics and Twins If 1 identical twin has Alzheimer's Disease, If 1 identical twin has Alzheimer's Disease,

the other twin’s chances of developing it is the other twin’s chances of developing it is 60%. For fraternal twins, it is 30%60%. For fraternal twins, it is 30%

Identical twins are more likely to be similar Identical twins are more likely to be similar in the areas of extraversion and emotional in the areas of extraversion and emotional instability than fraternal twins.instability than fraternal twins.

Odds of divorcing if an identical twin has Odds of divorcing if an identical twin has divorced is higher than with fraternal twins.divorced is higher than with fraternal twins.

BUT, studies reveal that identical twins BUT, studies reveal that identical twins report being treated more alike than report being treated more alike than fraternal twins.fraternal twins.

Nature vs. Nurture????Nature vs. Nurture????

Biological vs. Adoptive Biological vs. Adoptive RelativesRelatives

Studies of adoptees reveal the following Studies of adoptees reveal the following information:information:– Personalities of siblings (whether biologically related Personalities of siblings (whether biologically related

or not) who grow up together, are generally not or not) who grow up together, are generally not similar.similar.

– In areas of agreeableness and extraversion, In areas of agreeableness and extraversion, adoptive children are more similar to biological adoptive children are more similar to biological parents than adoptive parents.parents than adoptive parents.

– Implies environment has less influence than Implies environment has less influence than heredity.heredity.

– Important to remember that adoptive homes are Important to remember that adoptive homes are less likely to be abusive, neglectful or subject to less likely to be abusive, neglectful or subject to divorce.divorce. Most adoptive children, while more likely to develop Most adoptive children, while more likely to develop

psychological disorder, thrive, especially when adopted at psychological disorder, thrive, especially when adopted at birth.birth.

Temperament and HeredityTemperament and Heredity Temperament:Temperament: a person’s characteristic a person’s characteristic

emotional reactivity and intensity.emotional reactivity and intensity. Temperament is apparent at birthTemperament is apparent at birth

– Easy:Easy: cheerful, relaxed, and predictable in cheerful, relaxed, and predictable in patternspatterns

– Difficult:Difficult: irritable, intense and unpredictable irritable, intense and unpredictable– Slow to warm up:Slow to warm up: tend to withdraw or resist new tend to withdraw or resist new

people and situations.people and situations. Temperament tends to persist over timeTemperament tends to persist over time Identical twins tend to have more similar Identical twins tend to have more similar

personalities than fraternal twins leading to personalities than fraternal twins leading to belief that heredity highly influences belief that heredity highly influences temperament.temperament.

HeritabilityHeritability

What is it?What is it?– Heritability is the extent to which Heritability is the extent to which

variation among individuals can be variation among individuals can be attributed to their differing genes.attributed to their differing genes.

– For example if height has a heritability For example if height has a heritability of 90%, the extent to which observed of 90%, the extent to which observed differences among people’s height can differences among people’s height can be contributed to genetics.be contributed to genetics.

– IT DOES NOT MEAN that 90% of your IT DOES NOT MEAN that 90% of your height is determined by genes.height is determined by genes.

Nature vs. NurtureNature vs. Nurture While some traits occur regardless of While some traits occur regardless of

environment (having 2 eyes or ears), environment (having 2 eyes or ears), others are only expressed in certain others are only expressed in certain environment due to environment due to a necessity to adapt. a necessity to adapt. – Calluses on laborers handsCalluses on laborers hands

A biological adaptation to frictionA biological adaptation to friction Human differences result from both nature Human differences result from both nature

and nurture.and nurture.– Eating disorders may be genetically influenced Eating disorders may be genetically influenced

but are must more prevalent in image but are must more prevalent in image obsessed Western cultures.obsessed Western cultures.

When Genes and Environment When Genes and Environment Interact…..Interact…..

It is the It is the interactioninteraction of genes and of genes and environment that may ultimately environment that may ultimately determine the end result.determine the end result.

Genetically influenced traits, such as Genetically influenced traits, such as temperament may lead to a specific temperament may lead to a specific environment (i.e. abusive or environment (i.e. abusive or nurturing)nurturing)

Our traits may cause us, as adults to Our traits may cause us, as adults to choose specific environments.choose specific environments.

Who are you drawn to….?Who are you drawn to….?

Evolutionary PsychologyEvolutionary Psychology

The study of the evolution of The study of the evolution of behavior and the mind using behavior and the mind using principles of natural selection.principles of natural selection.

Natural selection: the principle that, Natural selection: the principle that, among the range of inherited trait among the range of inherited trait variations, those that lead to variations, those that lead to increased reproduction and survival increased reproduction and survival will most likely be passed on through will most likely be passed on through the generations.the generations.

Evolutionary PsychologyEvolutionary Psychology

These adaptations that promote These adaptations that promote survival and reproduction are rooted survival and reproduction are rooted deeply in generations past.deeply in generations past.– Love of sweets believed to come from a Love of sweets believed to come from a

need of our ancestors to survive famine.need of our ancestors to survive famine.– Love of sweets reinforced by Love of sweets reinforced by

overprocessed, unhealthy junk foods overprocessed, unhealthy junk foods and contribute to growing obesity and contribute to growing obesity epidemic.epidemic.

Evolutionary ExplanationsEvolutionary Explanations

Gender differences in SexualityGender differences in Sexuality– A cross cultural study of 200,000 people in A cross cultural study of 200,000 people in

53 nations found that men everywhere 53 nations found that men everywhere strongly agreed to “I have a strong sex strongly agreed to “I have a strong sex drive” and “It doesn’t take me much to get drive” and “It doesn’t take me much to get sexually excited.” at a much higher rate sexually excited.” at a much higher rate than women.than women.

– 58% of men as opposed to 12% of women 58% of men as opposed to 12% of women in a study of nearly 5,000 Australians in a study of nearly 5,000 Australians agreed that they would be “comfortable agreed that they would be “comfortable and enjoy having “casual” sex with and enjoy having “casual” sex with different partners”.different partners”.


What are some evolutionary What are some evolutionary explanations for men’s attitudes explanations for men’s attitudes towards sex?towards sex?

Women view sex from a relational Women view sex from a relational standpoint, while men view it from a standpoint, while men view it from a recreational standpoint.recreational standpoint.– Historically, women chose partners Historically, women chose partners

wisely in order to reproduce; men chose wisely in order to reproduce; men chose “widely”.“widely”.


What do people find attractive in the opposite What do people find attractive in the opposite sex from a evolutionary perspective?sex from a evolutionary perspective?

Men are drawn to youthful looking women; Men are drawn to youthful looking women; waist roughly 1/3 narrower than their hips (a waist roughly 1/3 narrower than their hips (a sign of fertility). Teen boys often find older sign of fertility). Teen boys often find older women (of child bearing age) attractive.women (of child bearing age) attractive.

Women are drawn to men who will “stick Women are drawn to men who will “stick around”; mature, dominant, bold, affluent, and around”; mature, dominant, bold, affluent, and show the potential for long-term mating.show the potential for long-term mating.

Critiques of the Evolutionary Critiques of the Evolutionary PerspectivePerspective

Tends to have a “hindsight bias”; looking Tends to have a “hindsight bias”; looking to the past to answer questions now.to the past to answer questions now.

Does it suggest a strong genetic influences Does it suggest a strong genetic influences that undermines societal and personal that undermines societal and personal responsibility?responsibility?

Some studies have found that gender Some studies have found that gender differences are culturally specific (i.e. differences are culturally specific (i.e. culture of gender inequality vs. gender culture of gender inequality vs. gender equality will determine what you look for equality will determine what you look for in a mate.)in a mate.)

Experience, Parents and Experience, Parents and PeersPeers

While genetic predisposition plays a While genetic predisposition plays a part in who we are, it is our part in who we are, it is our experiences that complete the picture.experiences that complete the picture.

Neural connections are directly Neural connections are directly affected by our experience.affected by our experience.– Insufficient interaction may result in less Insufficient interaction may result in less

neural connections.neural connections.– Ex. If we are not exposed to language Ex. If we are not exposed to language

before adolescence, we will have great before adolescence, we will have great difficulty acquiring language.difficulty acquiring language.


PARENTING MATTERS!!!PARENTING MATTERS!!!– A combination of genetics and parental A combination of genetics and parental

influences ultimately impact the influences ultimately impact the development of an individual.development of an individual.

– Family environment often shapes (but Family environment often shapes (but not always) children’s future parenting not always) children’s future parenting styles, vocational and academic styles, vocational and academic successes.successes.


Peers are highly influential through Peers are highly influential through life, but especially during childhood life, but especially during childhood and adolescence.and adolescence.– Preschoolers will eat undesirable food Preschoolers will eat undesirable food

when put at a table with peers who like when put at a table with peers who like it.it.

– Teens who smoke usually have friends Teens who smoke usually have friends who smoke.who smoke.

Cultural InfluencesCultural Influences

Culture:Culture: behaviors, ideas, attitudes, behaviors, ideas, attitudes, values and traditions shared by a values and traditions shared by a group of people and is transmitted group of people and is transmitted from one generation to the next.from one generation to the next.

Cultural Norms:Cultural Norms: rules for accepted rules for accepted and expected behaviorsand expected behaviors– Vary depending on culture of origin.Vary depending on culture of origin.– Video – Social NormsVideo – Social Norms


Variations across cultures Variations across cultures – Western Cultures: men shake handsWestern Cultures: men shake hands– Arab Cultures: men kissArab Cultures: men kiss– Western Cultures: wear shoes in the houseWestern Cultures: wear shoes in the house– Eastern Cultures: no shoes – considered Eastern Cultures: no shoes – considered

dirtydirty Variations over timeVariations over time

– Technology, pace of life, changed social Technology, pace of life, changed social norms related to marriage, race relations norms related to marriage, race relations


Individualist CulturesIndividualist Cultures Views self as Views self as

independentindependent Strives to be uniqueStrives to be unique Interested in personal Interested in personal

achievement/self esteemachievement/self esteem Have many Have many

relationships; often relationships; often casual; confrontation is casual; confrontation is acceptable.acceptable.

Behavior reflects own Behavior reflects own personality and attitudespersonality and attitudes

Collectivist CulturesCollectivist Cultures Views self as Views self as

interdependent (to interdependent (to group)group)

Strives to belongStrives to belong Interested in group Interested in group

goals, solidarity; family goals, solidarity; family dutyduty

Have few relationships; Have few relationships; close and enduringclose and enduring

Behavior reflects social Behavior reflects social norms and rolesnorms and roles

Cultural Influences on Cultural Influences on ChildrearingChildrearing

Childrearing practices reflect cultural Childrearing practices reflect cultural values that vary across time. values that vary across time. – 50+ years ago, in US, obedience, respect and 50+ years ago, in US, obedience, respect and

sensitivity to others was priority.sensitivity to others was priority.– Today, in US, children are encourage to be Today, in US, children are encourage to be

themselves, discover creative talents, prioritize themselves, discover creative talents, prioritize personal needs.personal needs.

Asian and African cultures value emotional Asian and African cultures value emotional closeness and strong sense of “family self”closeness and strong sense of “family self”– Encourage co-sleepingEncourage co-sleeping– Child’s behavior reflects upon the family Child’s behavior reflects upon the family

(shame or pride)(shame or pride)

Gender DevelopmentGender Development

Our biological sex at birth helps to Our biological sex at birth helps to define our gender – the combination define our gender – the combination of biological and social of biological and social characteristics by which people characteristics by which people define male or female.define male or female.

Gender is a perfect example of how Gender is a perfect example of how nature and nurture combined create nature and nurture combined create similarities similarities andand differences. differences.

Gender SimilaritiesGender Similarities

Genetically, males and females share Genetically, males and females share 45 of the 46 chromosomes. Only 1 45 of the 46 chromosomes. Only 1 pair are related to sex.pair are related to sex.

There are almost no differences There are almost no differences across the sexes in areas of across the sexes in areas of vocabulary, intelligence, happiness, vocabulary, intelligence, happiness, self esteem and cognitive self esteem and cognitive development.development.

Gender DifferencesGender Differences

Females:Females: Enter puberty 2 years Enter puberty 2 years

earlierearlier Live 5 years longerLive 5 years longer Have more body fatHave more body fat Smell fainter odorsSmell fainter odors Express emotions Express emotions

more freelymore freely 2x as likely to develop 2x as likely to develop

depression and depression and anxiety.anxiety.

Males:Males: 4x more likely to 4x more likely to

commit suicide or commit suicide or suffer with alcoholismsuffer with alcoholism

Much higher likelihood Much higher likelihood to be diagnosed with to be diagnosed with autism, color autism, color blindness, ADHD and blindness, ADHD and antipersonality antipersonality disorder.disorder.

Tendency to behave in Tendency to behave in more physically more physically aggressive ways.aggressive ways.

Gender DifferencesGender Differences Studies on gender differences in social Studies on gender differences in social

connectedness revealed:connectedness revealed:– Children: Boys tend to play in large groups with little Children: Boys tend to play in large groups with little

intimate conversation and engage in competitive play. intimate conversation and engage in competitive play. Girls play in small groups, often only with one friend and Girls play in small groups, often only with one friend and often imitate social relationships.often imitate social relationships.

– Adolescence: Girls spend more time with friends, more Adolescence: Girls spend more time with friends, more time on social networking internet sites than boys.time on social networking internet sites than boys.

– Adults: Women enjoy face to face talking and use Adults: Women enjoy face to face talking and use conversations to explore relationships. Men enjoy doing conversations to explore relationships. Men enjoy doing activities side by side and use to communicate solutions.activities side by side and use to communicate solutions.

– Women’s relationships tend to bind families together.Women’s relationships tend to bind families together.– Differences tend to peak in adolescence and diminish by Differences tend to peak in adolescence and diminish by

age 50.age 50.

Is Gender Nature or Is Gender Nature or Nurture?Nurture?

Levels of testosterone (male sex hormone) are Levels of testosterone (male sex hormone) are found in both sexes but are much higher in found in both sexes but are much higher in men. men. – Abnormal levels of testosterone can lead to more Abnormal levels of testosterone can lead to more

ambiguous gender identity.ambiguous gender identity. Cultural norms related to gender roles drive Cultural norms related to gender roles drive

the expectations about how males and females the expectations about how males and females should act.should act.– Scandinavian countries tend to embrace more Scandinavian countries tend to embrace more

gender equality than most countries; Middle Eastern gender equality than most countries; Middle Eastern and Northern Africian have the least gender and Northern Africian have the least gender equality.equality.

Gender IdentityGender Identity

Society lends itself to shaping gender Society lends itself to shaping gender roles and aids individuals in their roles and aids individuals in their resulting resulting gender identitygender identity – the sense – the sense of being male or female.of being male or female.

Social Learning TheorySocial Learning Theory assumes assumes children learn gender linked children learn gender linked behaviors through observing and behaviors through observing and imitating, then by being rewarded or imitating, then by being rewarded or punished.punished.

Social Learning is shaped by our Social Learning is shaped by our schemasschemas: : concepts that help us make sense of the concepts that help us make sense of the word. word.

How strongly influenced you are by your How strongly influenced you are by your schemas will ultimately determine your schemas will ultimately determine your gender identity.gender identity.

nature, nurture and human diversity chapter 4. nature vs. nurture psychology’s biggest question...

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