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Biological Determinants of Aggression. Overview of Biology/Physiology. Evolution (we already talked about) Genetic Neurotransmitters Hormonal Structural Biology/Physiology is probabilistic, not deterministic (so how to prevent aggression?). Genetics.
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Overview of Biology/Physiology • Evolution (we already talked about) • Genetic • Neurotransmitters • Hormonal • Structural Biology/Physiology is probabilistic, not deterministic (so how to prevent aggression?)
Genetics • Behavioral genetic research has shown genes influences individual differences in a wide range of human behaviors: cognition, academic achievement, personality, temperament, and so forth. • What about aggression? • How studied? • Heritability – proportion of variability attributable to genetic factors • Environmental – proportion of variability due to situation • Monozygotic twins – same egg • Dizygotic twins – different eggs • Adoption studies – Raised separately so test genes/situation separately • Adoptive siblings share environments but not genes • Biological siblings raised apart share genes but not environments • Confounded because imitations and co-offending in siblings • Findings • Clear evidence of heritability of criminality • Mixed results of heritability of aggression • Possible indirect effect through personality (impulsivity, dominance)
Genetics • A chromosome is an organized structure of DNA and protein that is found in cells. • Men – XY • Women – XX • Y-Chromosome Hypothesis • XYY • More criminals than non • Not more aggressive • More likely charged/convicted • X-Chromosome Hypothesis • XXY • Not more aggressive
Neurotransmitters • Dopamine • animal studies show large changes during aggressive behavior but not conclusive and not replicated in humans • Norepinephrine • Does control mood and arousal but no relationship to aggression • Serotonin • Lower levels of serotonin linked to aggression because lowers inhibitions so more impulsive • GABA • while it can inhibit behaviors, the findings are mixed in regard to aggression
Hormonal • Testosterone • sex hormone and anabolic steroid that has mixed evidence to producing aggression, more likely about status and dominance so indirect relationship to aggression • Premenstrual Syndrome (PMS) • inconclusive evidence its associated with aggression and criminality but see next slide for indirect relationship
Structural • Hypothalamus – located under the thalamus that controls several body functions, including feeding, breathing, drinking, and temperature. • Amygdala – an almond-shaped neural structure that regulates emotions. • Prefrontal cortex – implicated in planning complex cognitive behaviors • How to study? • Brain damage • Direct stimulation • Physiological Reactivity