Biological explanations

• What is selective breeding?

  Choosing animals with desired characteristics to breed over generations
• What is the purpose of selective breeding in animals?

  To practice high levels of aggression in specific breeds
• What specific genes are involved in determining levels of aggression?

  Genes that influence aggression levels
• What did Hood and Cairns (1989) find in their research on aggression in mice?

  They bred mice with significantly higher levels of aggression in just 4 generations
• How did the rearing environment affect aggression in Hood and Cairns' study?

  Aggression was reduced when mice were reared with siblings compared to isolation
• Why is generalizing findings from animal studies to humans considered debatable?

  Because the biological and environmental factors differ significantly between species
• What does the MAOA gene control?

  Production of the MAOA enzyme
• What is the role of the MAOA enzyme?

  It processes neurotransmitters like serotonin
• What is the low activity variant of the MAA gene called?

  MAOA-L
• How is the MAOA-L variant linked to aggression?

  It results in lower levels of MAO, which has been linked with aggression
• What did Brunner et al. (1993) study in their research?

  They studied an extended family in the Netherlands with aggressive male members
• What did Brunner et al. identify in aggressive individuals?

  A fault in the MA gene
• What did Cases et al. (1995) find in their knockout study?

  They could create highly aggressive male mice by disabling the MAA gene
• What was the procedure of Christiansen's (1977) twin study into aggression?

  • Analyzed criminality in 3586 pairs of twins in Denmark
  • Focused on twins born between 1881 and 1910
  • Compared concordance rates of criminality between MZ and DZ twins
• What were the concordance rates for male MZ twins in Christiansen's study?

  35%
• What were the concordance rates for female MZ twins in Christiansen's study?

  21%
• What does a concordance rate indicate in twin studies?

  The likelihood that both twins exhibit the same trait
• Why is it significant that the concordance rate is not 100%?

  It indicates that genetics is not the only factor influencing aggression
• How do MZ twins differ from DZ twins in terms of environmental influence?

  MZ twins are treated more alike and share more experiences
• What are the strengths and weaknesses of using twin studies in aggression research?

  Strengths:

  • Provide insight into genetic influences
  • Allow comparison of MZ and DZ twins

  
  

  Weaknesses:

  • May not account for environmental differences
  • Assumes equal treatment of twins
• What did Hertias find regarding the MAA-L gene and aggression?

  It is associated with greater aggression
• What did the study involving men with the high activity variant of the MAA gene reveal?

  They exhibited aggressive moves in a competitive game
• What is a counterpoint to the genetic influence on aggression?

  Environmental factors can significantly influence behavior
• How does the diathesis-stress model relate to aggression?

  It suggests that environmental factors affect the expression of genetic predispositions
• What is a problem with twin studies regarding environmental factors?

  They may not share the same environment to the same extent
• What does the research by Virkkunen et al. suggest about the MAOA-L gene and serotonin?

  It suggests that MAA-L may disrupt serotonin levels
• What is the complexity of the relationship between the MAA gene and aggression?

  The relationship is not yet fully understood
• What are the key points regarding the nature and nurture debate in aggression research?

  • Genetics play a role in aggression
  • Environmental factors also significantly influence behavior
  • The interaction between genes and environment is complex
• What is the limbic system?

  A network of structures in the brain
• Which structures are included in the limbic system?

  Hypothalamus and amygdala
• How is the limbic system linked to aggression?

  It is linked with reactive aggression
• What did Mpanopowou et al (2008) find regarding aggressive behaviors after amygdalectomy?

  Aggressive behaviors decreased between 33-100%
• What role does serotonin play in aggression?

  Serotonin has an inhibitory effect on aggression
• What happens when serotonin levels are low in the orbitofrontal cortex (OFC)?

  Individuals are less able to control their impulsive and aggressive responses
• What did Vichhunen et al (Gaalu) find in violent impulsive offenders?

  They found lower levels of serotonin
• What did Valtelli & Bernasconi (1979) discover about mice with low serotonin turnover?

  They were more aggressive than those with normal turnover
• What was the procedure of the key study by Gospic et al (2011)?

  • Lab method: 'Ultimatum game'
  • 'Proposer' offers to split money with a 'responder'
  • Responders' brains are scanned by fMRI
• What did Gospic et al (2011) find when responders rejected unfair offers?

  There was heightened response by the amygdala
• What effect did the drug benzodiazepine have in Gospic et al's study?

  It reduced the number of rejections
• What is a limitation of Gospic et al's findings?

  They are only correlational