Evolutionary Psychology by liuzedongsd


									The Nature & Nurture
     of Behavior
The Nature vs. Nurture
The Big Question:
How much are who we are—
 how we think, act and
 behave—shaped by nature
 (our genes) versus nurture
 (our environment)?
The Nature Nurture Debate
 Make two columns on a sheet
 of paper - 1) nature; 2) nurture
 Write characteristics you
 believe are mostly nature or
 mostly nurture in the
 appropriate column
 If the characteristic was
 nurture, what seemed to be the
The Nature vs. Nurture
The Simple View
 Behavior = genes + parental
The Realistic View
 Behavior = genes + prenatal
 influence + parental influence +
 nutrition + family income +
 education + culture + traumas +
 luck …
The Nature vs. Nurture
Two ways to determine the
 effects of nature versus

 Twin studies

 Adoption studies
The Nature vs. Nurture
 Identical twins are genetically
 – They share 100% of their genes.

 Fraternal twins are no more
 genetically similar than two
 – They share 50% of their genes.
Nature: Twin studies
 Identical twins are more
 similar than fraternal twins in
 – Abilities
 – Interests
 – Personality traits
    Extraversion (outgoing)
    Neuroticism (emotional instability)
Nature: Identical twins
reared apart
 Even identical twins reared
 apart have similarities in
 – Personality
 – Abilities
 – Interests
      Twin Studies

Comparing identical twins
separated at birth with
those reared together
Twin studies video
Nature: Adoption Studies
 Q: Are adopted kids more
  like their biological
  parents or their adopted

Adopted children’s personalities are
much more similar to their biological
parents’ personalities than to their
adoptive parents’ personalities.
Nurture: Environmental
 Prenatal environment
Nurture: Environmental
                            Parents matter
                            because they provide
                            experiences that can
                            lead to better brain
 Impoverished environment
                            After 60 days in an
                            enriched environment
                            with more toys, more
                            companions, and more
                            to explore, young rats
                            •7 – 10% bigger brains
                            •20% more synapses
 Enriched environment
Nurture: Other ways parents
Parents may not influence their
 children’s personalities much,
 but parents do influence their
  •Attitudes   •Interests
  •Values      •Education
  •Manners     •Discipline
  •Faith       •Responsibility
Nurture: Other ways parents
 Parental influence is also
 more evident at the
 – Abused children versus very
   loved children
Peer influence

Peer influence may exceed
parental influence,
especially as children and
adolescents begin to spend
more time outside the home.

Siblings are also important
   “With us for the whole
Are Gender Differences
   Due to Nature or
Gender Differences—
Evidence for Nature
 – Linked to desire for status
   and dominant behavior
 – Leads to muscle growth
 – Females exposed to excess
   testosterone in utero prefer
   more masculine toys,
   activities, and careers
 – Related to spatial ability
Gender Differences—
Evidence for Nature
 Animal studies
 – Males found to be more aggressive
   among many species
 – Vervet monkeys show similar gender
   preference with toys as humans
 – Evidence for sex differences in
   spatial ability
Gender Differences—
Evidence for Nature
 Baby studies
 – Girls respond more to sounds of
   distress, have greater pain
   sensitivity and make more eye
   contact than boys in first week of life
 – Compared to girls, newborn boys
   more interested in looking at a
   physical object and less interested in
   looking at a face
Gender Differences—
Evidence for Nature
 The sad story of David Reimer
 (AKA John/Joan)
Gender Differences—
Evidence for Nurture
 Parents of boys more likely to
 report that they have
 mathematical talent than
 parents of girls (despite
 similar grades)

 Children with male names are
 more likely to be rated as
 strong, intelligent, and active
Gender Differences—
Evidence for Nurture
 Some evidence that
 differences in cognitive
 abilities have decreased
 over time
 Other societal attitudes,
 expectations, prejudices
Evolutionary Psychology
 Natural Selection

Evolutionary Psychology
 Goal of organism is to spread

 Behavior will reflect this goal.

 Is used to answer the “why’s”
 of human behavior.
Evolutionary Psychology
1.   You are on a boat that overturns. It contains
     your 5-year-old and 1-year-old children (of
     the same sex). The boat sinks and you can
     save only one. Whom do you choose to

2.   That same boat (you are slow to learn
     lessons) contains your 40-year-old and 20-
     year-old children (both of the same sex).
     Neither can swim. As the boat sinks, whom
     do you choose to save?
Evolutionary Psychology
3.   Would you rather marry (or have married)
     someone older or younger than yourself?

4.   Of the following six, which three are most
     important in the selection of your mate?
     Circle the answers.
     a. good financial prospects
     b. physical attractiveness
     c. good looks
     d. ambition and industriousness
     e. a caring and responsible personality
     f. an exciting personality
Evolutionary Psychology
5.   You and your spouse are the proud parents
     of a new child. The grandparents are
     ecstatic. Who do you think will be kinder to
     the child?
     a. The mother of the mother
     b. The mother of the father

6.   Who will mourn more at the death of a
     child? Give the answer for each pair.
     a. father or mother
     b. parents of the father or parents of the
     c. younger parents or older parents
Evolutionary Psychology
 Across cultures, men are more
 sexually promiscuous and
 more likely to initiate sexual
 contact than women.

 Buss cross-cultural study
Evolutionary Psychology
• Buss cross-cultural study
  • Men preferred attractive physical features
    suggesting youth and health
   Women preferred resources and social
 Study of 37 different cultures:
     Characteristics         Characteristics preferred
    preferred by males:             by females:
1. Kindness and              1. Kindness and
   understanding                 understanding
2. Intelligence
                             2. Intelligence
3. Physical attractiveness
                             3. Exciting personality
4. Exciting personality
                             4. Good health
5. Good health
                             5. Adaptability
6. Adaptability
                             6. Physical attractiveness
7. Creativity
                             7. Creativity
8. Desire for children
                             8. Good earning capacity
9. College graduate
                             9. College graduate
10.Good heredity
                             10. Desire for children
11.Good earning potential
                             11. Good heredity
12.Good housekeeper
                             12. Good housekeeper
13.Religious orientation
                             13. Religious orientation
Singh Waist-to-hip Ratio
                  – Which of
                    these figures
                    did men rate
                    as most
     True or False?
1.   People’s differing divorce risks are about 50% attributable
     to genetic factors

2.   Adopted children’s personality traits are more similar to
     their adoptive parents than to their biological parents.

3.   Two children in the same family are on average as
     different from one another as are pairs of children selected
     randomly from the population.

4. In many places around the world, females are more likely
   than males to initiate sexual activity.

5.   A child who hears English spoken with one accent at home
     and another at school will end up with the same accent as
     his or her peers, not his or her parents.

6.   Even when families discourage traditional gender-typing,
     children still organize themselves into “boy worlds” and
     “girl worlds,” each guided by rules for what boys and girls

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