2. I.B. Learning Outcomes
■ I can explain how much our genes impact our
behavior.
■ Possible Essay Prompt:To what extent do genetics
impact human behavior?
3. ToWhat Extent
True NotTrue
Consider the merits or otherwise of an argument or concept. Opinions and
conclusions should be presented clearly and supported with appropriate
evidence and sound argument.
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.
5. Definition of a Gene
■ Genes are the working subunits of DNA. Each gene
contains a particular set of instructions, usually coding
for a particular protein or for a particular function.
6. Inheritance
■ Each offspring inherits traits from their parents.
■ 46 Chromosomes – 23 from Mom, 23 from Dad
■ ~20,000-25,000 genes
7. Key ideas about Genetics
■ Genes that we inherit from our parents give rise to
physiological functions which contribute to physical and
behavioral characteristics.
■ One Gene does not lead to a behavior, it can be a
building block towards that behavior.
9. Twin Studies
■ Identical Genetic Make Up
■ Different Environments
■ Look for similarities and differences between monozygotic
twins
■ Nature & Nurture
■ Is It All In the Genes?
10. Raine & Baker (2007)
■ Aim:To investigate the impact of genetics on antisocial behavior
(bullying, cruelty, aggression, etc.).
■ Method:
– Participants: 1,210 twins in California.
– Gave a behavioral survey to the twins, their parents, and their
teachers of the twins to measure for antisocial behavior.
– Used a statistical measure to compare the rankings of fraternal and
identical twins’ correlations.
11. Raine & Baker (2007)
■ Findings: Regardless of the reports they used (twins,
parents, or teachers) the results always showed a 50%
heritability rating.
■ Conclusion: About half of the antisocial behavior of
the participants could be traced back to genetics.
■ Explanation?CriticalThinking?
12. Grove et al. (1990)
■ Aim:To measure the genetic impacts on antisocial
behavior.
■ Method:
– Participants: 32 sets of separated identical twins.
– Conducted tests, questionnaires, and surveys to
measure antisocial behavior in each individual.
13. Grove et al (1990)
■ Findings:
– Adults: 21% of antisocial behavior was attributed to
genetics.
– Children: 41% of antisocial behavior was attributed to
genetics.
■ Conclusion: While genetics play an important role in shaping
antisocial behavior, the environment plays a larger role.
■ Explanation? CriticalThinking?
14. Serotonin
■ A neurotransmitter with the function of stabilizing mood and
maintaining “balance” in the brain.
■ Low levels of serotonin have been linked to depression,
anxiety, and other personality disorders.
15. MAO-A Gene
■ Codes for Serotonin in the Brain.
– Low Activity: Low amounts of Serotonin
– High Activity: High Amounts of Serotonin
■ Impacts the development of the Amygdala.
■ Also known as the “Warrior Gene” because those who
have a variation of it do not feel the calming effects of
serotonin.
16. Ferguson et al. (2011)
■ Aim:To investigate the relationships between the MAOA
gene, exposure to violence, & violent behavior.
■ Method:
– Participants: 398 Males in New Zealand who had been
demonstrated with Antisocial Behavior.
– Performed a genetic test when they were 28-30 years old.
– Surveyed the men for exposure to violence/trauma as
children & their own violent behaviors.
17. Ferguson et al. (2011) cont.
■ Findings:
– Those who had Low-Activity MAOA Gene were significantly
more likely to commit violent crimes than men with the High-
ActivityGene if they had experienced trauma.
■ Conclusion
– Low-Activity MAOA Gene &Trauma increase the rates of violent
behavior.
■ Explanation? CriticalThinking?
18. Epigenetics
■ Epigenetics means that factors beyond genes, including diet, stress,
lack of exercise, or living with an abusive parent, get inside genes
and alter their function in the body.
■ Put simply…Our experiences can change the way our genes function.
These changes can last for an entire life and be passed onto our
offspring.
19. Moore et al (2013): Epigenetics & Stress
■ Aim:To investigate the how the grooming behaviors of rat mothers
impact the effects on stress reactivity in offspring.
■ Method:
– Researchers observed mother rats care for their children and
recorded whether they were High-Groomers (HG) or Low-
Groomers (LG).
– Observed the ability for the offspring to respond to stress.
– Researchers also took non-biological baby rats and placed them
with mothers with different grooming patterns.
20. Moore et al (2013): Epigenetics & Stress
■ Findings:
– Rats with LG mothers displayed abnormal patterns in their DNA that silenced genes
that coded for their stress response.
– Non-Biological rat babies paired with a LG mother also showed these same changes
and struggled to deal with stress.
■ Conclusions:
– The environment that rats are raised in create epigenetic changes to individuals and
can lead to changes in their behavior.
■ Explanation?CriticalThinking?
21. Sandi et al (2012)
■ Aim:To investigate how stress of parents can alter the
genetics of generations of offspring.
■ Method
– Researchers exposed a group of male rats to extreme
stress (fox feces scents in their cages and being placed
on a tall tower in open spaces) at random intervals over
the course of a week.
– Observed the behavior of males after stress and the
behavior of their offspring.
– Offspring never met their father.
22. Sandi et al (2012)
■ Findings:
– Stressed father rats were excessively aggressive
towards their female cage-mates, even when those
females displayed submissive behavior.
– The offspring of the stressed fathers displayed similar
aggressive behavior even though they never met their
father.
■ Conclusion:The stressful experiences of parents can
imprint genetic differences in offspring and lead to
aggressive behavior.
23. Gapp et al (2016)
■ Aim:To investigate whether enriched environments can lead to epigenetic changes in
mice.
■ Method:
– Placed mice fathers in stressful experiences and then bred.
– Father mice were then placed in enriched environments and bred again.
– The behavior and genetics of the father mice and their offspring were then
compared.
24. Gapp et al (2016)
■ Findings:
– The father mice showed antisocial behavior after the stressed environment and
passed these traits onto the the stressed offspring.
– After exposure to an enriched environment, the father mice showed improved
behavior and their enriched offspring showed similar positive behavior.
– Stressed offspring had less glucocorticoid receptor in the hippocampus, while the
enriched offspring showed more of these.These control the stress response.
■ Conclusions:The environment of a parent can lead to epigenetic changes both for the
positive and negative.
■ Explanation?CriticalThinking?
25. Microlab Discussion Questions
■ To what extent is an individual’s genetics responsible for
their behavior? What evidence is most important when
determining your stance on this question?
■ What role should genetics play in the legal system?
■ In what ways can our understanding of genetics and
epigenetics be applied to areas of public policy and life
outside of the legal system?
26. Antisocial Personality Disorder
■ A condition that leads to a general lack of empathy for others, a
disregard for the rights of others, a lack of guilt, and often a disregard
for laws or social morals.
■ Psychopaths: Lack of connections with others but are able to present
charming personalities. Often times very successful and can appear
normal. Crimes are often highly calculated.
■ Sociopath: Easily agitated and nervous. Can often make limited
connections with others. Holding down jobs or gaining an education
is difficult. Crimes are often disorganized and spontaneous.
27. Bucholtz et al (2017)
■ Aim:To measure the brain activity and structure in psychopathic criminals when faced
with risk taking.
■ Method:
– Used a mobile fMRI machine to record brain activity of 49 inmates who had
committed violent crimes.
– Asked participants to participate in a risk taking decision where they decided
between an immediate & risky choice or a long-term & safe choice.
28. Bucholtz et al (2017)
■ Findings:
– Participants who showed the most pscyhopathic behavioral tendencies showed
increased activity in the striatum and less activity in the frontal lobe.
– Participants with the most activity in the striatum showed higher rates of risk
taking.
■ Conclusion:
– Psychopaths favor risky decisions due to increased activity in their striatum which
causes them to overvalue potential rewards.
■ Explanation
