Nature vs. Nurture
(via)
or
“Why we are who we are”
Dr. Swoap
Intro to Psychology
Fundamental Question
How are we
shaped by
both our
heredity
and
life history?
Behavior Genetics
•Attempts to explain
individual differences
–Twin studies (U of M) (see
Fig. 6.3)
–Adoption studies
Behavior Genetics
–Heritability: The proportion of variation
among individuals that we can attribute to
genes
–Temperament and Personality: Were you born
that way?
•Video Sci Amer #23 “Bringing up Monkey”
Evolutionary Psychology
•How does natural
selection work with
regards to behavior?
–Survival-oriented
behavior is passed on
Evolutionary Psychology
and sexual behavior
•Survey:
–Question 1: A sunny afternoon on vacation…
You are relaxing by the ocean. A person you
don’t know, but whom you think is really goodlooking, comes up to you and says: “I find you
really attractive. I’d like to sleep with you
tonight.” What would you do/say?
–Question 2: How often do you think about sex?
How often do you think
about sex?
Love in bloom
• Amidst the festivities of a grand party, a
young guy notices a strikingly beautiful girl
and is immediately obsessed….
• He approaches her and begins to flirt
boldly…. She tries to deny him, but soon is
flattered by his attention and finds him quite
attractive…
Romantic feelings kindle rapidly….
• By the time he departs the scene, with just a
few kisses, these two have exchanged fewer
than a hundred words; yet, both are swooning
with sensations of falling, desperately, in love.
• All their mental processes – thinking, planning, goals,
feelings, and motivations – have been suddenly
transformed….these brains have been completely
gripped by this brief encounter.
Longing, obsession, and desire…
• In the hours after this meeting, these two can not
stop thinking about each other
• The intensity of desire is so strong that each would
happily forego food, sleep, comfort, and all competing
pleasures, simply to be in each other’s presence
again
Shakespeare (1595) was dramatizing one of the normal tensions of
adolescence and development of sexual motivations.
SEX: Nature via Nurture
•Energizing and directing arousal
•Interplay of internal and external stimuli
•Internal: Hormones, brain structures,
neurotransmitters, imagined stimuli
•External: Environmental and
sociocultural factors
Environmental
Influence
–Five ways we are shaped along with genes:
1.
2.
3.
4.
5.
Prenatal environment
Early experience
Peer Influence
Culture
Gender influences
Keep in mind that our genes influence the nurture
and experiences we seek. (My children and their
temperaments influence my parenting.)
Environmental
Influence
–Five ways we are shaped along with genes:
1. Prenatal environment influences?
2. Early experience
Multiple studies emphasize the importance of
stimulating experience &/or touch: Both
enhance brain development (as does physical
activity)
Rosenzweig et al., 1972)
2. Early experience -continued
Multiple studies emphasize the
importance of stimulating experience
&/or touch: Both enhance brain
development (as does physical activity)
(massage therapy with preemies)
Environmental
Influence
–Five ways we are shaped along with genes:
3. Peer influence factors? (e.g., man in elevator)
4. Culture
–Examples?
• Food preferences, personal space,
aggression/violent behavior
• Obesity
–Cultural influences combined with a
genetic predisposition to store fat
Obesity Trends* Among U.S. Adults
(*BMI  30, or ~ 30 lbs overweight for 5’4” woman)
*Go to CDC slide show on “Obesity trends”
Nature via Nurture in Obesity
ENERGY IN
ENERGY OUT
Increase in
availability of
high density foods
(sugar/fat are cheap)
Decrease in workrelated activities
Decrease in activity
of daily living
Increase in size
Decrease in cost
BODY MASS
Genetic predisposition to store fat
Nature via Nurture in Obesity
“Our jeans no longer fit our waist
because our genes no longer fit our
environment”
5. Gender Influences
Why are you a male/female? (Besides the
obvious reasons…)
Gender is a social category of being male or
female.
Gender development
starts early
Is it a boy or a girl???
Interactive model of Gender
Development
Child’s traits &
Biological factors
Parenting
style
Socio-cultural
factors
Socialization and gender
• Differential gender socialization
• Gender and culture
– (e.g., rites of passage, expected
behaviors)