Human BehaviorHuman Behavior

Nature vs. NurtureNature vs. Nurture

Nature or Nurture?Nature or Nurture?

Why do men and women have such Why do men and women have such different attitudes about sex?different attitudes about sex?

Why do boys and girls play with Why do boys and girls play with different toys?different toys?

Why do you, the oldest, seem to be Why do you, the oldest, seem to be organized and responsible, while organized and responsible, while your youngest brother seems to be your youngest brother seems to be carefree and happily irresponsible?carefree and happily irresponsible?

Behavior GeneticsBehavior Genetics(Text Question #1)(Text Question #1)

Study individual behavioral Study individual behavioral differences. differences. (weigh effects of nature, nurture)(weigh effects of nature, nurture) Chromosomes: 23 / egg, 23 / sperm (threadlike Chromosomes: 23 / egg, 23 / sperm (threadlike

structures)structures)Composed of DNA (deoxyribonucleic acid)Composed of DNA (deoxyribonucleic acid)

Genes: 30,000 each / self-replicating Genes: 30,000 each / self-replicating units, synthesize proteins, (the building units, synthesize proteins, (the building blocks of physical developmentblocks of physical development

Gene complexes: many genes acting in Gene complexes: many genes acting in concertconcert

Genes: Influence physical make-up, Genes: Influence physical make-up, intelligence, aggressiveness, happiness etc.intelligence, aggressiveness, happiness etc.

Behavior GeneticsBehavior Genetics

Nature and GenderNature and Gender Gender DevelopmentGender Development

What determines male, female offspringWhat determines male, female offspring2323rdrd pair of chromosomes determine sex pair of chromosomes determine sexFemale=X, Male = X or YFemale=X, Male = X or Y

Fraternal, Identical Twins:Fraternal, Identical Twins:What’s the difference?What’s the difference?

Fraternal: (dizygotic)Fraternal: (dizygotic) Separate fertilized eggs Separate fertilized eggs

(50% shared genes- no (50% shared genes- no more genetic similarity more genetic similarity than normal siblings)than normal siblings)

Identical: Identical: (Monozygotic)(Monozygotic)

Single fertilized egg Single fertilized egg split in two = split in two = clonesclones

(100% shared genes)(100% shared genes)

Fraternal vs. Identical (#2)Fraternal vs. Identical (#2) Fraternal / Identical twin study findings- Fraternal / Identical twin study findings-

provide specifics for the following:provide specifics for the following: Alzheimer’sAlzheimer’s

Identical =60% / Fraternal=30%Identical =60% / Fraternal=30% Extraversion / neuroticismExtraversion / neuroticism

Identical more similar than fraternalIdentical more similar than fraternal Divorce ratesDivorce rates

Identical x5.5 vs. fraternal x1.6Identical x5.5 vs. fraternal x1.6 Schizophrenia Schizophrenia

50, 10, 3, 1 (identical, fraternal, sibling, stranger)50, 10, 3, 1 (identical, fraternal, sibling, stranger)

What are the limitations of these studies?What are the limitations of these studies? Genetics or environment? How do we Genetics or environment? How do we

differentiate?differentiate?

Gerald Levy and Mark NewmanGerald Levy and Mark NewmanBouchard Minnesota Twin Bouchard Minnesota Twin

StudyStudy

Levy and NewmanLevy and Newman

Bouchard’s Minnesota Twin StudyBouchard’s Minnesota Twin Study Reunited by shared acquaintanceReunited by shared acquaintance Upon meeting for first time:Upon meeting for first time:

Same mustache, sideburns, glassesSame mustache, sideburns, glasses Levey: college degree in forestry- Newman planned to but worked Levey: college degree in forestry- Newman planned to but worked

for city trimming treesfor city trimming trees Levey worked installing sprinker systems, Newman installed fire Levey worked installing sprinker systems, Newman installed fire

alarmsalarms Both were bachelors, same taste in womenBoth were bachelors, same taste in women Both only drank Budweiser (pinky wrapped underneath can, Both only drank Budweiser (pinky wrapped underneath can,

crushed can afterwards)crushed can afterwards) Hunting, fishing, beach, John Wayne movies, pro-wrestling, Chinese Hunting, fishing, beach, John Wayne movies, pro-wrestling, Chinese

food in wee hoursfood in wee hours Volunteer firefightersVolunteer firefighters Both raised Jewish, neither particularly religiousBoth raised Jewish, neither particularly religious When met- same remarks, at same time, same gestures- “spooky”When met- same remarks, at same time, same gestures- “spooky” He is he and I am I, and we are one…He is he and I am I, and we are one…

Adoption Studies (#5)Adoption Studies (#5)

What insight has adoption studies provided What insight has adoption studies provided regarding the influence of genetics on regarding the influence of genetics on

personality? (#5)personality? (#5) Environmental relatives / biological Environmental relatives / biological

RelativesRelatives Finding: subject’s personality reflected Finding: subject’s personality reflected

biological relatives, even when adopted biological relatives, even when adopted at birthat birth

Conclusion: people who grow up together Conclusion: people who grow up together don’t resemble each other in personalitydon’t resemble each other in personality

Why are two people raised together so Why are two people raised together so different???different???Confirmation of genes impact on personalityConfirmation of genes impact on personality

Environmental InfluenceEnvironmental Influence

So what traits does nurture So what traits does nurture influence?influence?ValuesValuesMannersMannersFaith / religionFaith / religionPoliticsPoliticsSocial viewsSocial views

Heritability (#6)Heritability (#6)

Extent to which difference between Extent to which difference between individuals can be attributed to genesindividuals can be attributed to genes

As environments become more similar, As environments become more similar, heredity as a source of difference heredity as a source of difference becomes more important (becomes more important (and vice versaand vice versa))

Heritable differences don’t often translate Heritable differences don’t often translate to group differencesto group differences

Temperament (#7)Temperament (#7)

Our emotional excitabilityOur emotional excitabilityTemperament traits tend to remain Temperament traits tend to remain

consistent through lifeconsistent through lifeStudies confirmStudies confirm

Genetic temperament helps form Genetic temperament helps form enduring personalityenduring personality

Nature Nature andand Nurture Nurture

Genes are self-regulating (respond Genes are self-regulating (respond and adapt to environment)and adapt to environment)

Individual differences almost always Individual differences almost always the result of both nature and nurturethe result of both nature and nurture– ““Gene and scene dance together”Gene and scene dance together”– Or, “nurture works on what nature Or, “nurture works on what nature

endows”endows”

Molecular Genetics (#8)Molecular Genetics (#8)

Identify specific Identify specific genes influence on genes influence on behaviorbehavior Weight, Weight,

extraversion, sexual extraversion, sexual orientation…orientation…

LD, depression, LD, depression, schizophrenia, schizophrenia, alcoholism…alcoholism…

Designer babies?!?!Designer babies?!?!

Evolutionary PsychologyEvolutionary Psychology

PremisePremise (Darwins’ ) natural (Darwins’ ) natural

selection shapes selection shapes our behavior, our behavior, thinking (over thinking (over time)time)

Certain traits, Certain traits, behaviors that behaviors that enhance survival enhance survival are passed on over are passed on over generationsgenerations

Questions to ConsiderQuestions to Consider

1.1. Why do infants start to fear strangers Why do infants start to fear strangers about the time they become mobile?about the time they become mobile?

2.2. Why are most parents so Why are most parents so passionately devoted to their passionately devoted to their children?children?

3.3. Why do so many more people have Why do so many more people have phobias about spiders and snakes phobias about spiders and snakes than guns and electricity?than guns and electricity?

4.4. Why are men quicker to perceive Why are men quicker to perceive friendliness as sexual interest?friendliness as sexual interest?

Dmitry Belyaev: Domestication of Dmitry Belyaev: Domestication of FoxesFoxes

Belyaev’s ExperimentBelyaev’s Experiment 30 males, 100 females30 males, 100 females Tamest 5% M, 20% FTamest 5% M, 20% F 30 generations30 generations Complete domesticationComplete domestication Now sold as house petsNow sold as house pets

Implications?Implications? When certain traits When certain traits

are selected that are selected that give an adaptive give an adaptive advantage, those advantage, those traits will prevailtraits will prevail

Gender and Sexual Attitudes / Gender and Sexual Attitudes / BehaviorBehavior

Studies:Studies: 1978, FSU- research assistants / proposals for 1978, FSU- research assistants / proposals for

casual sex with strangerscasual sex with strangers75% of men- yes75% of men- yes 0% of women- yes0% of women- yes

Questionnaire: casual sex with different Questionnaire: casual sex with different partnerspartners

48% of men- yes48% of men- yes 12 % of women- yes12 % of women- yes

How can we explain this radical How can we explain this radical difference in sexual attitudes between difference in sexual attitudes between the genders? the genders?

Gender Differences and SexualityGender Differences and SexualityNatural selection would suggest that each gender Natural selection would suggest that each gender

pursued attitudes and behaviors that perpetuated their pursued attitudes and behaviors that perpetuated their survival, and thus became part of our DNA over time.survival, and thus became part of our DNA over time.

Women- Women- relationalrelational Incubates, nurses Incubates, nurses

one infantone infant Wants protection, Wants protection,

assistance to assistance to ensure child’s ensure child’s survivalsurvival

Chooses Chooses wiselywisely

Men- Men- recreationalrecreational Perpetuate his Perpetuate his

genes (spread his genes (spread his genes through genes through other females)other females)

Chooses Chooses widelywidely

Boys, girls and toys…Boys, girls and toys…Nature or Nurture?Nature or Nurture?

Why do genders choose what they Why do genders choose what they do…?do…?

Nurture and GenderNurture and GenderNurture influences our sense of Nurture influences our sense of

gender by…gender by… Gender identityGender identity (one’s sense of being male (one’s sense of being male

or female)or female) Gender roles-Gender roles- traditional behaviors, duties traditional behaviors, duties

of gendersof genders Gender-typingGender-typing: expectation or assignment : expectation or assignment

of traditional male, female rolesof traditional male, female roles

Social learning theory (Observation, Social learning theory (Observation, imitation)imitation)

Genes rule…?? Genes rule…??

In terms of personality, In terms of personality, environmental factors typically environmental factors typically account for less than 10% of account for less than 10% of children’s differences. (Key is how children’s differences. (Key is how parents and peers influence those parents and peers influence those traits.)traits.)

Nurture and Early DevelopmentNurture and Early Development

Early experience matters!Early experience matters!Fosters neural connectionsFosters neural connectionsExperience preserves activated neural Experience preserves activated neural

connectionsconnectionsUnused ones degenerate (Unused ones degenerate (pruningpruning))Excess “connectors” in youth make kids Excess “connectors” in youth make kids

more capable of mastering certain more capable of mastering certain tasks.tasks.Example?Example?Foreign language, (Accent and grammar) Foreign language, (Accent and grammar)

visual perception, musical instrumentsvisual perception, musical instruments

Rat Studies Rat Studies Rosenzweig and KrechRosenzweig and Krech

Isolated, impoverished vs. social, enriched environmentIsolated, impoverished vs. social, enriched environment Young ratsYoung rats

Findings:Findings: Obvious differences in behavioral activity and curiosityObvious differences in behavioral activity and curiosity Heavier, thicker brain cortex (brain weight increased 7-10 Heavier, thicker brain cortex (brain weight increased 7-10

percent and # of synapses increased 20%!)percent and # of synapses increased 20%!)

Impoverishedenvironment

Rat braincell

Rat braincell

Enrichedenvironment

Premature BabiesPremature Babies

Neonatal unitsNeonatal unitsMassage therapy stimulates growthMassage therapy stimulates growthSpeeds departure from hospitalSpeeds departure from hospital

Nurture’s Sway…Nurture’s Sway…Cultural InfluencesCultural Influences

IndividualismIndividualism Self: IndependentSelf: Independent Life Task: Discover, Life Task: Discover,

express one’s express one’s uniquenessuniqueness

What matters: Me, What matters: Me, personal achievement, personal achievement, rights, freedoms, self-rights, freedoms, self-esteemesteem

Coping method: Coping method: change realitychange reality

Relationships: Many, Relationships: Many, often temporary, often temporary, confrontation confrontation acceptableacceptable

Behavior: Reflects one’s Behavior: Reflects one’s personality, attitudepersonality, attitude

CollectivismCollectivism Self: InterdependentSelf: Interdependent Life Task: fit in, perform Life Task: fit in, perform

role, obligationsrole, obligations What matters: Us, group What matters: Us, group

goals, family duty, social goals, family duty, social responsibilityresponsibility

Coping method: Coping method: Accommodate to Accommodate to realityreality

Relationships: Few, close Relationships: Few, close and long term, harmony and long term, harmony valuedvalued

Behavior: social norms Behavior: social norms and rolesand roles

Cultural InfluencesCultural Influences

IndividualismIndividualism CollectivismCollectivism