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Myers’ PSYCHOLOGY

(7th Ed)

Chapter 3 The Nature (H) & Nurture (E)

Of Behavior

James A. McCubbin, PhDClemson University

Worth Publishers

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Ch. 3 The Nature (H) & Nurture (E)

Of BehaviorHumans’ shared common human behaviors in

tropics…or Arctic:EX’s: Ppl prefer sweet to sour tend toward off-spring-protecting behav. best female features show health & youth

(reproductive potential) at about 8 mos., fear strangers ppl know frowns from smiles from surprise ppl laugh, cry, worship…etc.In ? of heredity (nat.) vs. environment (nurt.):

both very important, but which is which & how to study?

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Genes: Our Biological Blueprint Chromosomes: threadlike structures made of

DNA…DNA contains the genes -Genes trigger biology…which triggers

behav. -46 chromosomes per cell nucleus: 23 from

mom, 23 from dad (**Except reprod cells…X + Y) -chrom. made up of DNA (de-oxy-ribo-nucleic

acid)

-DNA made of genes…traits come from gene complexes (many genes acting together) 2 strands-forming a “double helix” Helix held together by bonds between

pairs of nucleotides

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Genes: made of nucleotidesEach chrom. has at least 50 mill. ! -4 nucleotide letters: A, T, C, & G

Genome: complete instructions for making an organism consisting of all the genetic material in its chromosomes (Human Genome Project)

All humans have 99.9% of same DNA …(chimps share 95% of human DNA) -but variations at gene sites in DNA

give us uniqueness (gene complexes)

Evolu. psy. + behavior genetics look at how we are the same--and different--thru this genetic make-up

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Genes: Location & Composition:Cell contains nucleus..contains chromosomes …made of DNA …containing genes (gene complexes) …contain nucleotides (A,C,T,G)…

Nucleus Chromosome Gene

Cell DNA

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Evol. Psy: the study of the evolution of behavior

& the mind, Darwin’s ideas of natural selection

EX: see taming the fox (p. 101) thru genetic breeding

-selected traits to dominate…dog breeders (& others) do this

Natural selection: says there are a certain range of inherited trait variations

-those that lead to increased reproduction & survival will most likely be passed on to succeeding generations

Antibiotic-resistant bac.: Even bacteria can select the changes that will prevail

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Natural selection & humans: Come from mutations (random errors in

genes): EX: fear of heights & snakes = better ability to survive…& many ppl still fear these

-humans very similar, but we notice differences

Early on ?'s for ancestors: what to eat, whom or what to trust, whom should I mate?

Nat. selection looks at genetic design that solves

adaptive problems , leading to survival & spread of these genes

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Evolutionary theory: only about 35% of Amer. public thinks Darwin's theories are supported by evidence, but "…virtually no contemporary scientist believes he was wrong"

Evol. psy. look at many ?'s

(see B-p. 103)

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Sexuality: Gender: Cross cultural studies: in psychology, the characteristics, whether biologically or socially influenced, by which people define male (M) &

female (F)…many cross cultural done to study this… Men preferred attractive physical features: suggests

youth & health Women preferred resources & social status WHY?

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In gender: (p. 103-4) Which gender desires more frequent sex, thinks more about sex…etc.? (duh…)

A: men… w/ few exceptions in world -(top 104)….& experiment w/ avg. looking

at Florida St. Men: lower threshold for seeing warm

response as sexual come-on…”Oh yeah! She wants me!”

-can = sex. harassment…or date rape

Evol. explanation: Nat. selection = women more relational, men more recreational

While 1 woman growing & caring for 1 infant, men still “wide open”

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What attracts M/W world-wide? (= Crs.–Cul.?) M: woman w/ waist at least 1/3 narrower than hips (= fertility) --tend to be risk-takers in all areas Maybe showing off to attract? (105) {T.Sawyer? }W: look for those bold, dominant, & affluent males…WHY?

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In singles ads: F offer looks & seek status M offer status & seek looks F also look for potential long-term stability… “dads over

cads” …esp. smart F! Why? b/c more likely to send genetic material into future

Critiques of the Evolutionary Explanation: Though M’s think about different partners, M & F look for

v. similar traits in a permanent mate Bonding to make off-spring better is strong pattern…kids

do better w/ 2 good parents.. -Chimps, though, have F that mate w/ many: fool males

so they will accept all kids since males more likely to harm & murder other males’ kids?

Evolutionary perspective: WHY is it an example of hindsight bias??

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Behavior Genetics: Study of the relative power & limits of genetic &

environmental influences on behavior

Environment: every non-genetic influence, from prenatal nutrition to the ppl & things around us…our experiences--school, church, society, gov’t., econ.,

resources, expectations, nutrition (or lack of), culture, world events, etc

**Best way to look at the differences betw. heredity vs. environ.:

-twin studies (both Fraternal & Identical)

-adoption studies

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RE: M dominant over F: There are exceptions to this…but way more of "the rule"

But…changes in society today? Does this mean it has to stay this way?

Humans are NOT locked in to behaviors… Humans have huge ability for & tendency to

adapt, so new rules can be established

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Behavior Genetics Identical Twins single fertilized egg that splits

in 2, creating 2 genetically identical organisms

-”nature’s closest’ who share DNA, uterus, birth date, & cultural history

-monozygotic: 1 egg, 1 sperm

Fraternal Twins develop from separate eggs genetically no closer than

brothers & sisters, but they did share the fetal environ., cultural history & birth date

-Dizygotic: 2 eggs, 2 sperm

Identicaltwins

Fraternaltwins

Samesex only

Same oropposite sex

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Inborn traits studies: 24,000 twins show ID twins much more similar than fraternal twins in extraversion (outgoingness) & neuroticism (emotional stability)

Strong correlations between fraternal vs. ID twins in divorce (1.6 X vs. 5.5 X more likely if twin divorces)

BUT…are ID twins often treated more alike = __?__ variable?

However, even if consider this, doesn’t seem to have effectSeparated twins studies: EX’s: Read about the “2

Jim’s” (p. 109)!!! 2 twins, 1 Catholic Nazi, 1 Caribbean Jew: but still amazing similarities

Researchers have located about 170 separated ID pairs & 200 fraternal pairs

Studies show separated ID twins ARE much more similar than separated fraternal twins…….but NOT as similar as ID’s raised together …. So this indicates what?

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Critics: Twins share womb so this is part of their environment (“birth environment”)

Also say ID twins tend to be placed in similar homes

-And you can find anecdotal facts that are coincidences for almost anyone (“6 degrees of separation?”)

Adoption studies: another way to look at heredity (nature) vs. environment (nurture)

Adoptees personality traits: These are more like biological parents’ traits than adoptive parents’ traits

Look at 2 groups of relatives: biological parents/siblings + adoptive parents/sibs

*Findings: personality traits & behaviors much more like biological rather than adoptive

Behavior genetics FOCUS: Personality traits & DNA

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So does parenting matter? Not much w/ traits (Traits are mostly innate)But YES w/… -attitudes -manners -values & beliefs -faith -politicsAdoptive parents (environment) have influenceParenting DOES matter…& adoptees can do better b/c there is

less divorce in adoptive homes (checked for stability in relationships)

Temperament: How a person typically responds emotionally

How excitable & reactive we are: Easy going? Difficult, tense, fidgety, quiet? (see stats p.

112)

Heredity influences temperament…It IS a physiological reaction, involving w/

heart rate, BP, etc. (Which NS?) -Twin studies support this-- ID vs. fraternal

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Heritability: Proportion of variation among individuals attributed to

genes; % of variation w/in a population

May vary, depending on the range of populations & environments studied

Extent to which a trait is likely to be inherited… NOT what % of your IQ is inherited Group differences: RE: behavioral traits in differing

groups (M/F, different racial groups, economic…): not necessarily explain these

EX: Some groups more aggressive? Well…Look at height + weight …ARE highly

heritable: But there are recent increases b/c of better

nutrition (environ. factor) …& then fast food culture…

A new social context can also can cause changes in behaviors (like aggression… mild mannered to aggressive)

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Nature enables nurture: How interaction works to shape ppl: We all eat…what we eat depends on cultural

interactionOther EX: Wear shoes? = soft feet

Always barefoot? = calluses, tough, cracked…

Interaction: dependence of the effect of one factor (like environ.) on another factor (like heredity

p. 114: twins: ID + fraternal:

Explain these statements: 1. “Children experience us as different parents, depending on their own qualities…”

2. Also as we grow older …..we tend to select environments that fit w/ our natures

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Molecular Genetics:

Subfield of biology that studies the molecular structure & function of genes -tries to ID specific genes influencing behaviors

EX: p. 115: Obesity: How would molecular geneticist

consider this? (remember to consider interaction!) Those at risk for at least a dozen diseases can

now be ID’ed

Soon may be able to ID genes for schizophrenia, depression, alcoholism, reading disability, sexual orientation, etc.

(THINK: Would you want to know??)

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Environmental influences: Genetics: responsible for 40-50% of personality traits, so

rest is from…? P. 116-7: 30-yr.-old ID twin “neat-freaks” ? Parents: Blame or credit? “Where did we go wrong??” --pushy parents? over-protective? uninvolved? How much help or how much damage? A lot is

unknown-more extreme = more effects: really bad or really

good… Resiliency: How kids can survive terrible

situationsPrenatal /early environment: Womb = 1st environmental

influence (see slide 23)

Experience & brain development: a) more experiences = more neural connections -another study: brain weight up 7-10 % + # of

synapses up 20% …after just 60 days!b) touch & massage: handling, loving on rats--& babies

—stimulates weight gain (sign of thriving, growing) & neurological development

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Environmental Influence: Renner & Rosenwieg (& Krech) Study: Experience affects brain development (NOTE: was replicated twice to be sure!) Rats w/ the most “toys” were the neural

winners… more experience = more connections

Impoverishedenvironment

Rat braincell

Rat braincell

EnrichedEnvironment:

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Experience & brain development (cont’d.):

c) early experiences: some things have “window of opportunity”…if you miss that window closing, then you lose best chance…

EX: vision: those w/ early cataracts & later removal…

--cells allotted to vision either died out or given over

to other functions d) later experiences: “trained” monkeys brains show different activity & connections than untrained

(#22) As you learn a skill & work hard on it--music, language skills, athletics, etc.—areas become specialized & more developed to reflect that

-so the more we use our brains—surely early, but later also—the more we develop it… use it or lose it!

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Birth (“early) environment: there are 2 different placental arrangements in ID twins: 1 set (2/3 of all ID twins) shares placenta (b) 1 set doesn’t (a)

Set w/ shared placenta twins tend to have more similar personality than those w/ separate placentas

Theories as to why? Food supply? Oxygen? See P. 118

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Environmental Influence: Wiring up those neurons!!

A trained brain: Learning a task increases connections in an area A: scan b4 learning task B: scan after learning task

(a connection is made!)

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Environmental Influence…con’t.

Peer influence: As kids mature, peers (part of environment) gain

influence

Dr. Judith Harris: Said peers influence more than parents (EX’s p. 120:

foods language accents smoking)

Note: Many other psychologists disagree w/ this…

Parent’s Power: Parents have effect in choosing/influencing peer groups

by: schools neighborhoods, etc. AND giving good guidelines in society (religion, values,

morals…)

Culture:

Culture:

Enduring behaviors, ideas, attitudes, & traditions shared by a large group of ppl …

& transmitted from one generation to the next

In diverse culture, understanding differences is more important—

EX: US & Canada Japan: 126 mill.

People, 99% Japanese—less diversity

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Environmental Influence

Culture variations: p. 122: Look at EX’s of differences others see in our culture… things we see as “normal”

Terms (Cultural influence…cont’d.) Norms: understood rule for accepted, expected behavior Personal Space: buffer zone we like to maintain around our

bodies (Playing “Space Invader?”) Memes: self-replicating ideas, fashions, & innovations

passed from person to person Communication: EX: Iraqi misunderstanding US position RE:

Kuwait (p. 123) --also see tourist signs

Time variations: past vs. present…20 generations’ difference? Or even 2?? (changes since 1960? + & - )

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Culture & child-rearing: kids “obey”… or adventurous? -Western cultures let kids “discover” themselves…But used to stress more obedience, respect, manners, etc. Collectivist cultures (grp oriented) vs. individualistic cul.--Asian, African & Lat. Amer.: collectivist…more

cooperative, family oriented family 1st, not individual Shame the family = shame on you! “M & D will be disappointed …”: US/Italy=7%; Austral.=14%; Taiwan /Japan=25%

Though cultures vary, all tend to have stable kids…Similar devel. across Grps: looking at cross-cultural

research gives clues to her. (nat.) vs. envirn. (nurt.)

EX: Afr.Amer. men & high BP…Is it a biological “race difference” or……a cultural diet diff.?

Disorder differences come from…? IQ differences? Aggression? All possible Nature/Nurture ?’s for psy research

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The Nature & Nurture of Gender

X Chromosome: in BOTH M’s & F’s: F have 2 M have 1

-1 from each parent = female child Y Chromosome: sex chromosome found

only in M X from the mom, Y from dad = M child-7 wks.in utero, biological sex is triggered…

again at 4 - 5 mosP. 126-7: Is the behavior of these girls due to prenatal

hormones? F embryos (rats, monkeys) injected w/ M hormones

show aggressive M behavior……So early exposure to “wrong” hormones changes

behaviors????At least 1 X chrom. is essential for life..Though XX = F & XY = M, sometimes these

combinations don’t come out right…

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Abnormal sex chromosome patterns: SCA’s: sex chrom. abnor.

-Turner’s syndrome: F w/ only 1 X (XO); ultra feminine…but sterile

-Kleinfelter’s syn.: 1-2/1000 M’s have extra X (XXY); tall, hi-voiced, sterile

-double Y syn.: 1/1000 M’s = extra Y; XYY; V. tall; low IQ

-fragile X syn.: part of X is so thin it seems about to break; most severe retardation levels; it is highly heritable

Testosterone (from M endocr. Sys.…M gonads (testes) most important of the M sex hormones; in both M & F additional testosterone in M stimulates growth of M

sex organs in the fetus & develop. of M sex characteristics in puberty

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The Nature & Nurture of Gender

Role: set of expectations (norms) about social position, defining how ppl in that position should behave

Gender Role: expected M & F behaviors: Who does what in a society? Work? Kids--& sick kids?

Laundry?

Nomadic vs. agricultural societies: Usually limits F’s power & rights (p. 128)

These are changing…especially in MDC’s b/c of needs & demands

AND especially among college educ. PopulationsEX’s of each aspect?-----------------------------------------

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Gender Identity: our sense of being M or F, based on social categories in a society …what we ARE & it will not change…

Gender-typing: Extent to which we acquire traditional masc. or fem. role

EX: M = “man’s man”; macho vs. sissy F = “prissy” ...or tom-boy...butch

Know these 2 & differences betwn.: How we “learn” gender: Gender Schema Theory (we classify): kids learn their

cultures ideas about M or F …& adjust behavior accordingly

a) cultural learning of gender … which leads to… b) ..gender schema (seeing self & world thru gender lens) …which leads to… c) gender organized thinking + gender-typed behavior

Social Learning Theory: says we learn social behavior by observing & imitating …AND by being rewarded or punished for right/wrong behaviors

EX’s: “You baked cookies! Good girl!” “Quit being a girlie-boy!” etc.)

rewards + punishments = gender-typed behaviors

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Two theories of gender typing

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The Nature and Nurture of Gender

Differences in Gender & Culture: graph: 1994

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The Nature & Nurture of Gender

Differences over time: graph: 2002

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Postscript: Reflections on nature & nurture:

Genes form us…& it seems true that our genes come from…

Variations natural selection heredity evolution

“Genes & experiences: 2 ways of doing the same thing..

…wiring the synapses.” J. Le Doux

But not only nature (heredity) forms us, but also the experiences (nurture…envir.) we have…

And these come from many things…. not just 1 or 2 things …& not just our parents & peers, but

many combinations of things

**For those of you who worry about theories of naturalism & evolution taking away from spiritual aspects…be sure to read from bottom of 131 – 132.

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AP Psy R/W Folders Assignment # : Identifying Genes for Disorders Textbook,

p. 115 1) What are some of the risks of selecting

for certain traits, genders, etc? 2) a) Would you want to know if you were

positive for a gene like depression, bipolar disorder, or schizophrenia?

b) Why or why not?3) a) What is meant by a “designer baby?” b) Why is the idea of a “designer baby” not likely? c) How do you feel about this?