Chapter 4: Nature, Nurture,
Human Diversity (Part 1)
Eliza Kronenberger, Kayla Russell, Abby Lagunov

A biological aspect of taste that humans prefer is the
taste of sweets.

We start to fear strangers at around 8 months old.

3 universal behaviors of humans:

-dancing/feasting

-singing/worshipping

-playing sports/games
Behavior
Genetics/Environment

Study differences and weigh effects in the interplay
of heredity and the environment.
Cell Nucleus

Every cell nucleus in the body contains a genetic
master code for the entire body.
Definitions:

DNA: Complex molecule containing genetic
information that makes up chromosomes.

Chromosome: Threadlike structures made of DNA
molecules, contain genes.

Genome: Complex instructions for making an
organism, consisting of all genetic material in an
organism’s chromosomes.
“We shared half our genes
with the banana.”

Proves that slight variation change in genetics causes
vast differences.
Types of Twins

Identical Twins: Twins who develop from a single
fertilized egg, splits in 2 creating 2 genetically
identical organisms.

Fraternal Twins: Develop from separate fertilized
eggs- genetically no closer than ordinary
brothers/sisters, but share fetal environment.
Fraternal Twins

Fraternal twins are not any more similar than an
ordinary brother/sister.
Alzheimer’s Disease

If a person has Alzheimer’s disease, an identical twin
has a 60% chance of getting this disease. A fraternal
twin has a 30% chance.
Matt McGue and David
Lykken Study (1992)
Followed divorce rates of 1,500 same-sex, middle-aged
twin pairs.

Results: Fraternal twin who is divorced- odds of
divorce go up 1.6x (compared to not divorced twin)

Identical twin who is divorced- odds of divorce of
other twin go up 5.5x
Importance of Genes

Genes do not matter in explaining individual
differences.
Quote: Bouchard

“In some domains it looks as though our identical
twins reared apart are… just as similar as identical
twins reared together. Now that’s an amazing finding
and I can assure you none of us would have expected
that degree of similarity.”

Even if twins are separated, biologically (with genes)
interests are similar.
Bouchard’s Critics Theory

Separated fraternal twins do not exhibit similarities
comparable to those of separated identical twins.
Twin Studies

Twin study results give us a greater appreciation for
genetic influences.
Genetic/Environmental
Relatives

Genetic- Biological parents/siblings

Environmental- adoptive parents/siblings
Does environment impact
personality?

Adoptees more similar to biological parents than to
adoptive parents.
Quote:

“Mom may be holding a full house while Dad has a
straight flush, yet when Junior gets a random half of
each of their cards his poker hand may be a loser.”

Child is not guaranteed the best traits of each parent,
but gets a random selection… No genetic legacy!
Adopted Children
Most adopted children thrive because…

-Attatched to adoptive parents

Many score higher than biological parents on an
intelligence test
Benefits of Adoption

Children grow up happier

More self-giving than average
Temperament

A person’s characteristic emotional reactivity and intensity.
Temperament

Temperament persists over time.
Temperament

Biologically rooted temperament helps form our
enduring personality: one form of a gene that
regulates the neurotransmitter serotonin predisposes
fearful temperament and inhibited child.
Heritability

Proportion of variation among individuals that we
can attribute to genes. The heritability traits may
vary.
Environment Similarities

As environments become more similar, heredity (as a
source of differences) become more important.
Self Regulating Genes

Genes react, rather than acting.
Eating Disorders

Human differences result from both genetic and
environmental influences.

For example, eating disorders are genetically
influenced- some people are at more of a risk than
others.
Gene-Environment
Interaction

Genes and experiences are both important, but they
interact.

Interaction: Interplay that occurs when the effect of
one factor (such as the environment) depends on
another factor (heredity).
“Heredity deals the cards;
environment plays the hand.”

Biology starts off a person’s life- personality develops
and changes them from the society around them.
Nature/Nurture

Think “Nature VIA Nurture” instead of “Nature Vs.
Nurture”.
Molecular Genetics

Subfield of biology that studies molecular the
molecular structures and functions of genes.
Molecular Behavior
Genetics

Goal: to find some of the many genes that influence
normal humane traits, such as baby weight, sexual
orientation, extraversion, and also explore
mechanisms that control gene expression.
“Missing Women”

Men/boys are favored in India and China... Girl
children are often killed or given away. This is a
problem now because there are too many boys in this
area and a shortage of girls.
Evolutionary Psychologists

The study of the evolution of behavior and the
mind, using principles of natural selection.
Natural-Selections

The principle of the survival of the fittest
Belyeav & Trut: Fox Study

In this study, wild foxes were collected and the most tame of these
were mated with one another. Over a few decades, these animals
became completely domesticated.
Mutations

A random error in gene replication that leads to a change
Universal Actions

Example: A loved one of any culture in the world is
greeted in the same way.
Predisposition to Tastes

Humans are predisposed to love sweet and fatty tastes.
Outcome?

This love of sweet/fatty foods has led to obesity in Western cultures.
Harms of Industrial
Revolution

Our bodies are not wired for this type of world- with
such mass productions.

It has also adjusted us to live by a clock schedule.
Darwin

All current scientists agree with Darwin’s ideas.
Two Questions of
Evolutionary Psychologists?

What are the mental differences between men and women?

How do genes shape our current environment? (Nature VIA Nurture)
Gender difference in
Sexuality

Men have a much stronger sex drive than women.
Pryor’s study on attitudes
towards casual sex:

Discovered that about 58% of men favored casual sex, while only
34% of women did.
Fischstein’s study on
sexual thoughts:

About 46% of men think about sex throughout the whole day.

This is about the same for both Canadians and Americans.
3 Differences between gay
men and lesbian women:

Gay men report more interest in un-committed sex compared to
women

More responsive to sexual stimuli

More concerned with physical attractiveness
Clark and Hatfield’s Study:

Had university students wander around the campus and say that other
random students were attractive.

¾ of men agreed: 50% to a cup of coffee, 75% to sex

No women agreed.
Approaches to sex:

Men: Approach is more recreational

Women: Approach is more relational
4 characteristics that men
find attractive:

Healthy women

Fertile (young)

Smooth skin

Youthful shape
Women preferences of
men:

13 year old boy 17/18 year old girl

25 year old boy Same age girl

50 year old boy Younger women
2 Characteristics that
women find attractive:

Being affluent/wealthy

Dominant
Long-Term Mates

Evolutionary psychologists believe that women prefer long term
mates because of their investments in joint offspring.
Roney’s Study on Women
and Baby Pictures:

In this experiment, women skillfully discerned which men most
liked looking at baby pictures, and they rated those men higher as
potential long-term mates.