Genetics & Nature vs. Nurture

Nature vs. NurtureIs there a biological reason why girls tend to like dolls and

clothes? Is there a biological reason why boys tend to like toy cars and guns? Or is this something that children are nurtured

to like by their parents and other societal factors?

Nature vs. Nurture DebateNature:

Our genetics determine our behavior. Our

personality traits and abilities are in our

“nature.”

Nurture: Our environment, upbringing, and life

experiences determine our behavior. We are “nurtured” to behave

in certain ways.

Nature vs. Nurture DebateNature:

We genetically inherit physical traits from our

parents, but we also inherit personality traits,

intelligence, and preferences.

Nurture: The household and city we grew up in, how we were

raised by our parents, teachers, and friends -

these are environmental factors that determine

who we are.

Nature vs. Nurture Debate

A Point for Nature: “Studies show that

we inherit genes that are related to certain

personality traits.”

A Point for Nurture: “Often Identical twins

grow up to have very different

personalities and preferences.”

?

Nature vs. Nurture Debate

Today we know that nature and nurture BOTH help shape our behavior. The question

for today’s debate is this:

Which one has the GREATER influence on human behavior?

Pair-ShareDo you think you share any personality traits

with your parents or grandparents?

Behavioral Genetics:The study of the effects of heredity on behavior.

Behavioral genetics tries to answer this question: To what extent are our abilities, personality traits, sexual

orientations, sociability, and psychological disorders determined by genes inherited from our parents?

Will this child be

more like her birth

parents or adoptive parents?

Twin StudiesTwin Studies are used to help us answer the question of “nature

vs. nurture.” Because identical twins share the same genetic makeup, we can assume that differences between them are due

to environmental factors.

Twin Studies Pair 1:

Same DNASame Environment

However, twins often grow up in very similar environments.

If intelligence is the same, it’s hard to tell if it is due to genetics or

environment.

Pair 2:Same DNA

Same Environment

If intelligence is different, we can assume that there are tiny

differences in environment (different friends, time spent studying, etc.)

that caused the difference.

Twin Studies Pair 4:

Different DNASame Environment

One sibling is adopted.If intelligence is the same,

it is likely due to environment. If intelligence is different, it is

likely due to genetics.

Pair 3:Same DNA

Different Environment

Twins adopted by different families grow up in different environments.

If intelligence is the same, it is likely due to genetics. If intelligence is different,

it is likely due to environment.

Twin Study Results?

Extraverted

Neurotic

Agreeable

Conscientious

Correlation (How strongly twins shared the same traits)

0 0.1 0.2 0.3 0.4 0.5

Identical Twins (99% DNA match) Fraternal Twins (50% DNA match)

Open to New Experiences

Pair-ShareDo you think a Twin Study is a reliable way to

test whether our behavior is determined more by nature (genetics) or nurture (environment)?

Why or why not?

What do studies tell us?

Study: 1,252,387 genetic markers were tested for

association with personality traits. The results indicated

that only 1% of genetic variants significantly

contribute to personality variation. This means our

individual genetic differences do not significantly contribute to personality trait variation.

(Verweij et al., 2010)

Personality:

What do studies tell us?

Study: 1,252,387 genetic markers were tested for

association with personality traits. The results indicated

that only 1% of genetic variants significantly

contribute to personality variation. This means our

individual genetic differences do not significantly contribute to personality trait variation.

(Verweij et al., 2010)

This was NOT a twin study: it was a genome-wide association study done in 2010. This is

where each person gives a sample of DNA, from which millions of genetic variants are read in order to see if certain genes are associated with diseases

or personality traits.

Other Studies That relate to the “nature, nurture” question

Study: Men who carry one or two extra copies of a gene called allele 334 often behave differently in relationships

than men who lack this gene variant. Men with an extra copy of the gene felt a weaker, less permanent attachment

to their partners, and were more likely to be unfaithful. Men who had two

copies of allele 334 were also twice as likely to have had a marital or

relationship crisis in the past year than those who lacked the gene variant.

(Karolinska Medical Institute, Stockholm).

Nature? (Genetics) or Nurture? (Environment)

Study: Novelty-seeking

behavior (impulsive decision-making, the need to explore, lack

of organization) is related to the

presence of a certain gene in the body, and is highly inheritable.

(Golimbet et al., 2007).

Other Studies That relate to the “nature, nurture” question

Genes & Test ScoresIn a recent study at University college London, researchers

compared test scores of high school students to their genes. The study found that 58% of the variation on student test

scores was due to genetic factors.

The research drew on the exam scores of more than 11,000 16-year-olds. Researchers also compared the scores of identical and non-identical twins in a supplementary study.

Genes & Success Does having amazing genes lead to future

career success and wealth?

This boy had genius parents.

Do you think his genes will have a greater

impact on his life, or his environment?

Genes & SuccessStudies show that for children living in poverty, it did not matter whether

they had good genes or not. The negative impact of the environment almost always played a greater role in their future success than their

genes.

For children in middle class and wealthy homes, having good genes

became very important to determining their future success.

Genes played a much greater role in the future success of each child.

Genes & Success

Researchers concluded that for children in harsh living conditions, it is harder for exceptional genes to “shine through.”

(Eric Turkheimer, 2003)

Feral Children

Feral Children are those who lived away from human contact

from a very young age, and have little or no experience of human care,

loving or social behavior, or

human language.

Feral ChildrenHomework:

Investigate it yourself:What can we learn from Feral

Children about nature vs. nurture?

Research at least one feral child, and write a paragraph (at least 5

sentences) about what feral children can teach us about

nature vs. nurture.

Submit by sharing a google doc with Ms. G before the start of

our next class.

Examples: Genie Wiley

Oxana Malaya Kamala & Amala Prava the Bird Boy

…