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Aggression: The Role of Nature

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  1. Aggression: The Role of Nature • Soundtrack • Bohemian Rhapsody (Queen) • Mack the Knife (Bobby Darin) To what extent is aggression caused by internal (innate, genetic, or biological) Factors For students who participated in the survey earlier in the semester: 2nd part to be handed out on Tues. Study Guide for Exam 4 is now available

  2. Is it aggression? • Exercise

  3. What is aggression? • Aggression: Intentional behavior aimed at causing either physical or psychological pain. • Key feature: Intention • Not the same as “assertive” or “ambitious” • Examples: • Beer bottle at party • Drunk driver

  4. Why might people behave aggressively? • Is aggression inborn? • Instinct theorists • Freud: Aggression innate, destructive • Freud: Death instinct (Thanatos) = innate impulse for self-destruction. Opposite of life instinct (Eros). • Lorenz: Aggression innate, but adaptive. • Ethologist. Emphasized that aggressive instinct facilitates the individual’s survival, reproduction.

  5. Instinct theories • Instinct theories are NOT widely accepted. • Problems with assuming that aggression is innate

  6. Problems w/Instinct Theories • Humans vary greatly in aggressiveness. • Cross-cultural differences (groups in South Seas vs. Yanomamo in South American; Iroquois and social change)

  7. Problems w/Instinct Theories • Regional differences in aggressive behavior • Culture of honor: Homicide rates for males are significantly higher than those for white northern males, especially in rural areas. But this is true only for "argument-related" homicides.

  8. Culture of honor experiments (Dov Cohen, Richard Nisbett & colleagues) • IV: A confederate “accidentally” bumped into the participant, and called the P an insulting name (or no incident in the control condition). • DVs: P’s guess about evaluator’s ratings of his masculinity; his physiological response to stress; and his behavior • Results: Southerners in insult condition were than northerners to think they would be seen as less masculine, experienced increased cortisol and testosterone, and were slower to move out of the confederate’s way in a very narrow passageway.

  9. Problems w/Instinct Theories • If aggression is a human instinct, then it is hard to account for this variability both within and between cultures.

  10. Problems w/Instinct Theories • Circular reasoning: • Why do sheep herd? Because they have a herding instinct. • Doesn’t explain the phenomenon, just names it.

  11. Biological influences on aggression • Neural influences • AMYGDALA -- associated with aggressive behavior in humans and in lower animals. • When electrically stimulated, docile animals become violent; when neural activity in the amygdala is blocked violent animals become docile.

  12. Neural influences: Interaction w/environment • Social factors can influence the impact of these neural mechanisms. • If a male monkey is in the presence of other, less dominant monkeys, he will attack the other monkeys when the amydala is stimulated. • But if the amygdala is stimulated while the monkey is in the presence of more dominant monkeys, he will not attack but will run away instead.

  13. Chemical/hormonal influences • Testosterone • Injection of testosterone will increase aggression in animals (cause and effect relationship in non-human animals)

  14. Testosterone in humans Dabbs and colleagues • Naturally occurring testosterone levels are higher among prisoners convicted of violent crimes than those convicted of nonviolent crimes. • Once incarcerated, prisoners with higher testosterone levels violated more prison rules • Compared fraternities within a given college: those known to be more rambunctious, less socially responsible, and more crude had the highest average testosterone levels. • Correlational: Questions about direction of causality and third variables

  15. Behaving aggressively also can increase testosterone • 3rd variables: Violent prisoners may differ in many ways from less nonviolent prisoners (e.g., in stress, family history, etc.) • However, people opting for sex reassignment show more aggression as testosterone is increased. (Still correlational and not a random sample – expectations may influence)

  16. Genetic influences • Are people who are more aggressive genetically different from those who are less aggressive? • Can breed animals to be more or less aggressive

  17. Genetic influences • Twin studies • Identical (monozygotic) twins have identical genetic makeup. • Fraternal (Dizygotic) twins are no more similar genetically than any other siblings. • Twin studies are based on the assumption that identical twins should show greater similarity on any trait that is presumed to be inherited than fraternal twins.

  18. Genetic influences • Identical twins twice as likely as fraternal twins to be similar in degree of criminal activity. • Christiansen: 7000 twins born in Denmark 1881-1910 • 35% identical vs. 13% fraternal showed similarity in serious criminal activity • Problems: • 65% identical twins did not have similar records • Identical twins may have more similar environments than do fraternal twins.

  19. Genetic/biological vs. environment • Debate: • Aggressive behavior results from an interaction between genetic/biological factors and environmental factors, but aggression is more powerfully influenced by genetic and/or biological factors. • Aggressive behavior results from an interaction between genetic/biological factors and environmental factors, but aggression is more powerfully influenced by environmental factors.

  20. Heredity vs. environment • Example: Serial killer, Joel Rifkin • Researchers examine both environment and possible genetic basis (look at brain scans) • Video clip & discussion • To what extent do you think that Joel Rifkin’s killing was caused by genetic/biological factors or environmental factors?