Neural and Hormonal Mechanisms in Aggression

1. Neural and Hormonal Mechanisms in Aggression

2. 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!)

3. 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)

4. 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)

5. HORMONAL MECHANISMS • Testosterone • The male sex hormone • Influence aggression from young adulthood. • Research Studies – Dabbs et al (1987) Criminals – Higher testosterone levels has a history of primarily violent crimes

6. 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

7. HORMONAL MECHANISMS • Cortisol • Has a mediating effect on aggression-related hormones because it increases anxiety and social withdrawal. (Dabbs et al., 1991) • High levels of cortisol can inhibit testosterone levels.

8. STUDIES • Meta-analysis studies, showing the link between aggression and • A) Neurotransmitters • B) Testosterone

9. Reductionism • What is biological reductionism? • GENDER BIAS: Is aggression a male phenomenon?