Genetics & Behavior

Genetics & Behavior: Nature vs. Nurture

1. Genetics
& Nature vs. Nurture

2. Nature vs. Nurture
Is 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?

3. Nature vs. Nurture Debate
Nature:
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.

4. Nature vs. Nurture Debate
Nature:
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.

5. 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.”
?

6. 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?

7. Pair-Share
Do you think you share any personality traits
with your parents or grandparents?

8. 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?

9. Twin Studies
Twin 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.

10. Twin Studies
Pair 1:
Same DNA
Same 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.

11. Twin Studies
Pair 4:
Different DNA
Same 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.

12. 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

13. Pair-Share
Do 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?

14. 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:

15. 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.

16. 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).

17. 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

18. Genes & Test Scores
In 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.

19. 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?

20. Genes & Success
Studies 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.

21. Genes & Success
Researchers concluded that for children in harsh living
conditions, it is harder for exceptional genes to “shine through.”
(Eric Turkheimer, 2003)

22. 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.

23. Feral Children
Homework:
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
…