Transcript Of Behavior

Myers’ PSYCHOLOGY
(7th Ed)
Chapter 3
The Nature (H) & Nurture (E)
Of Behavior
James A. McCubbin, PhD
Clemson University
Worth Publishers
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Ch. 3 The Nature (H) & Nurture (E)
Of Behavior
Humans’ 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
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study?
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 nucleotides
Each 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
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genetic make-up
Genes: Location & Composition:
Cell contains nucleus..contains chromosomes
…made of DNA …containing genes (gene
complexes) …contain nucleotides (A,C,T,G)…
Nucleus
Cell
Chromosome
Gene
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
Identical
twins
Same
sex only
Fraternal
twins
Same or
opposite sex
 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
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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 effect
Separated 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
-politics
Adoptive parents (environment) have influence
Parenting 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 interaction
Other 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 situations
Prenatal /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
Impoverished
environment
Rat brain
cell
Enriched
Environment:
Rat brain
cell
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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:
language accents
smoking)
foods
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:
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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 mos

P. 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. Populations
EX’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.)
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 rewards + punishments = gender-typed behaviors
 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?
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