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

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.

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

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

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.

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; physiological response to stress; and behavior Results: Southerners in insult condition were more likely 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.

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

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

Biological influences on aggression Neural influences – AMYGDALA -- associated with aggressive behavior in humans and in lower animals. When electrically stimulated, docile animals__________________; when neural activity in the amygdala is blocked ______________become __________.

Neural influences: Interaction w/environment –Social factors can influence the impact of these neural mechanisms. –EX: If a male monkey is in the presence of other, _______dominant monkeys, he will ____________the other monkeys when the _____________is stimulated. But if the ___________is stimulated while the monkey is in the presence of ______dominant monkeys, he will ____________but will ________instead.

Chemical/hormonal influences Testosterone –Injection of testosterone will _________aggression in animals

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

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.

Genetic influences Identical twins twice as likely as fraternal twins to be similar in degree of criminal activity. Christiansen: 7000 twins born in Denmark –________identical vs.______ fraternal showed similarity in criminal activity Problems: –__________identical twins ____________similar records –Identical twins ___________________than do fraternal twins.

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.

Heredity vs. environment Example: Serial killer, Joel Rifkin Researchers examine both environment and possible genetic basis (look at brain scans) –Video clip