This document discusses how genetics can influence human behavior. It summarizes several key studies on genetics and behavior. The Minnesota Twin Study found that 70% of intelligence is attributed to genetic variation by comparing identical twins reared together or apart. Additionally, the Caspi et al. study found that individuals with two short alleles of the 5-HTT gene were more likely to be depressed following stressful events, showing how genetics can predict likelihood of depression. In summary, the document examines the role of genetics versus environment in determining human behavior and traits.

1. Genetics

2. I.B. Learning Outcomes
 B11- With reference to relevant research
studies, to what extent does genetic
inheritance influence behavior?
 I can explain how much our genes
impact our behavior.

3. Warm-Up Questions
 “Give me a dozen healthy infants, well-formed,
and my own specified world to bring them up in
and I'll guarantee to take any one at random and
train him to become any type of specialist I might
select – doctor, lawyer, artist, merchant-chief and,
yes, even beggar-man and thief, regardless of his
talents, penchants, tendencies, abilities,
vocations, and race of his ancestors. I am going
beyond my facts and I admit it, but so have the
advocates of the contrary and they have been
doing it for many thousands of years.”
-John Watson (Psychologist…not Sherlock’s buddy)

4. Behavioral Genetics
 The study of how the both genetics and
the environment contribute to individual
variations in human behavior.
 Genes do not cause behavior, they
create a predisposition towards it.
 Depression

5. Inheritance
 Each offspring inherits traits from their
parents.
 46 Chromosomes – 23 from Ma, 23 from
Pa
 ~20,000-25,000 genes

6. Mr. Bonica’s Piglets and
Behavioral Genetics

7. Twins

8. Separated Twin Studies
 Identical Genetic Make Up
 Different Environments
 Look for similarities and differences
between monozygotic twins
 Nature or Nurture
 Is It All in the Genes?

9. Minnesota Twin Study:
Bouchard et al. (1990)
 Learning Outcome: B11
 Aim: To determine the extent that
genetics impact the behavior.
 Method:
 Participants: Self-Selected MZ twins reared
together (MZT) and MZ twins that were
reared apart (MZA)
 Performed 50 hours of interviews, tests, and
surveys on participants.

10. Minnesota Twin Study:
Bouchard et al. (1990) Cont.
 Findings:
 Intelligence testing showed that 70% of
intelligence is attributed to genetic
variation.
 Conclusions:
 Intelligence among other characteristics
are to a large extent due to genetics
 Critical Thinking:
 Ethics
 Twins together = same environment?

11. Minnesota Twin Study:
Bouchard et al. (1990)
What is your response to the idea that our
genes can impact our behavior? What
does this say about you?
 Do you find these results to be surprising?
Why or why not?

12. I’m Not a Look Alike!

13. Segal (2012)
 Aim: To investigate if similar physical
features impact the personality traits of
humans.
 Method:
 Sent various tests and personality surveys to
subjects from Brunelle’s Art Exhibit.
 Stability, openness, extroversion,
agreeableness, and conscientiousness

14. Segal (2012) Continued
 Findings: Unrelated look-alikes showed
little similarities in self-esteem or
personality.
 Conclusions: Physical features do not
predict psychological traits.
 Critical Thinking?

15. Ethics of Genetic Research
 Anonymity and Confidentiality.
 Right to know who owns their genetic
material and with whom it will be shared.
 Informed Consent
 Genetic research could potentially be a risk
to the participants if misused.
 Genetic Research can reveal information that
is unexpected or a source of distress (Learning
that you are predisposed to depression can
lead to depression)

16. 5-HTT Gene
 A gene that is responsible for creating
proteins that influence the reuptake of
serotonin
 Long-Allele (57% of population)
 Short-Allele (43% of population)

17. Caspi et al. (2003)
 Learning Outcome: B11
 Aim: To determine whether the 5-HTT
gene predicts depression
 Method:
 Followed a group of adolescents for several
years and measured for stressful events.
 When they were 26, they tested them for
depression.

18. Caspi et al. (2003)
 Findings:
 Individuals who had a two short 5-HTT alleles
were more likely to be depressed following
stressful events.
 Conclusion:
 Genetics can predict the likelihood of
depression in individuals.
 Critical Thinking

19. Levenson (2013)
 Aim: To determine the role of the 5-HTT gene
in marital satisfaction
 Method: Followed couples since 1989 and
surveyed them on marital satisfaction.
 Finding: Individuals with a short 5-HTT allele
were more likely to be unhappy in an
unhealthy relationship or happy in a healthy
relationship.
 Conclusion: Short Allele = More influenced by
environment.