Genes contribute to about half of individual variations in antisocial behavior, according to twin studies. While genes may increase predisposition, they do not determine behavior alone. Studies found genetics account for 50% of antisocial behavior, but less impact for separated twins, showing environment also influences behavior. Research links low-activity MAOA genes interacting with childhood trauma to increased violence, suggesting genetics and environment combine to impact antisocial behavior.

1. AN INTROTO
GENETICS
Genetics and Antisocial Behavior

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.

8. Twins

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. 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.

19. Questions to Consider.
■ Should violent psychopaths be punished more or less
severely if their behavior can be blamed on brain
differences or genes?
■ To what extent is nature or nurture responsible for
violent crimes?
■ To what extent are crimes determined or the result of
free will?
■ To what extent do genetics impact violent behavior?