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Neural and Hormonal Mechanisms in Aggression Neurotransmitters • Chemicals that enable impulses in the brain. • Transmit form one area of the brain to the other. • Low levels of SEROTONIN and high levels of DOPAMINE have been linked to aggression in animals (and humans!) SEROTONIN • Thought to reduce aggression by inhibiting responses to emotional stimuli. • Low levels of serotonin in the brain is associated with increased susceptibility to impulsive behaviour. • Some drugs alter serotonin levels and increase aggressive behaviour. • Mann et al. (1990) gave drug dexfenfluramine to 35 healthy subjects – increased hostility )in males) DOPAMINE • Some link between high levels of dopamine and aggression. • Use of amphetamines linked to increases in aggressive behaviour (Lavine, 1997) • Antipsychotics reduce dopamine activity have reduced aggressive behaviour in violent delinquents (Buitelaar, 2003) HORMONAL MECHANISMS • • • Testosterone The male sex hormone Influence aggression from young adulthood. a) Research Studies – Dabbs et al (1987) Criminals – Higher testosterone levels has a history of primarily violent crimes HORMONAL MECHANISMS testosterone b) The challenge hypothesis – Wingfield et al (1990) in monogamous species testosterone levels should only rise above the baseline breeding level in response to SOCIAL CHALLENGES (male-male aggression) A testosterone surge is expected with an increase in aggression HORMONAL MECHANISMS • Cortisol • Has a mediating effect on aggressionrelated hormones because it increases anxiety and social withdrawal. (Dabbs et al., 1991) • High levels of cortisol can inhibit testosterone levels. STUDIES • Meta-analysis studies, showing the link between aggression and • A) Neurotransmitters • B) Testosterone Reductionism • What is biological reductionism? • GENDER BIAS: Is aggression a male phenomenon?