Neural and Hormonal Mechanisms Flashcards
(12 cards)
neural and hormonal mechanisms in aggression
many biological explanations of aggression focused on the structure and function of the brain and nervous system (neural mechanisms) as well as activity within the endocrine system (hormonal mechanisms)
what are the neural mechanism explanations
(1) role of the limbic system (structure)
(2) role of seratonin (chemical)
neural mechanisms - the role of the limbic system
- introduction
a neural mechanism that has been linked to aggression is the limbic system.
limbic system = network of structured beneath the cortex (subcortial) including the amygdala, hippocampus, and hypothalamus involved in regulating emotion and behaviour such as aggression.
neural mechanisms - the role of the limbic system
- amygdala
amygdala = most important structure, emotional centre in the brain.
plays a key role in how an animal responds to environmental challenges.
reactivity of the amygdala in humans is an important predictor of aggressive behaviour.
if the amygdala malfunctions (eg tumour, damage, or atypical development) levels of testosterone can be raised, making aggressive behaviour more likely.
neural mechanisms - the role of the limbic system
- hippocampus
hippocampus (forming long term memories), also been linked to aggression.
memories processed here allows animals to compare the conditions of a current threat with similar past experiences when responding.
impairment of the hippocampus prevents the nervous system from putting threats into context, may cause the amygdala to respond inappropriately, resulting in aggressive behaviour.
neural mechanisms - the role of the limbic system
- STRENGTHS
P) support for role of amygdala from Groves and Schlesinger (1982)
E) amygdlectomy (surgical removal of amygdala) reduces aggression in previously violent individuals
E) however, a side effect is loss of emotion, initiative, and enthusiasm
L) suggests the amygdala doesn’t directly cause aggression but is involved in processing associated emotions such as anger
P) support for role of hippocampus from Raine et al (2004)
E) MRI scans of gc of violent offenders that were caught (unsuccessful psychopaths) showed their hippocampus differed in size in either hemisphere unlike violent offenders who evaded the law (successful psychopaths)
E) asymmetry may have impaired ability of hippocampus and amygdala to work together leading to impulsive aggression in the unsuccessful psychopaths
L) supports that memories processed in the hippocampus influence aggressive behaviour
neural mechanisms - the role of serotonin
another possible neural influence in aggression is the neurotransmitter serotonin which has a widespread inhibitory effect throughout the brain.
normal levels of seratonun typically inhibits the firing of the amygdala, which helps to control fear, anger and other emotional responses.
low levels of serotonin remove this inhibitory effect -> individuals not able to control impulsive and aggressive behaviour (‘serotonin deficiency hypothesis’)
low levels of serotonin associated with an increased susceptibility to impulsive aggression and violent suicide
neural mechanisms - the role of serotonin
- STRENGTHS
P) support from Raleigh et al (1991)
E) vervet monkeys fed on diet high in tryptophan (increases serotonin levels in brain) decrease in aggression
E) monkeys fed on diets low in tryptophan has increase in aggression
L) difference in aggression could be attributed to their serotonin levels
P) support from Bond (2005)
E) antidepressant drugs that raise serotonin levels tend to reduce impulsive aggression
L) serotonin has a direct impact on aggression
P) support from Scerbo and Raine (1993)
E) meta analysis of 29 studies
E) consistently lower levels of seratonin in highly aggressive children, adults, individuals who had attempted suicide
L) low serotonin leads to a variety of impulsive, aggressive behaviours
hormonal mechanisms - the role of testosterone
as aggression is generally higher in males than females, research has focused on the androgen gc of hormones (male sex hormones) eg testosterone
although it’s produces mainly by the testes in males, it does occur in females.
associated with development of masculine features, as well as with aggression due to its action on brain areas involved in controlling aggression.
‘basal model of testosterone’ suggests that TT causes a change in a persons level of dominance.
more TT that a person produces, more competitive and dominant
so, a man with high TT levels may take part in anti-social behaviour such as fighting, as a way of expressing dominance.
although TT levels are higher in males, the relationship between TT and agg is not limited to males.
studies show a positive relationship between TT and agg and related behaviours (eg competitiveness) in women.
although women have lower TT levels, they are more influenced by smaller changes in the levels than men.
dual-hormone hypothesis: TTs role in status-relevant behaviour should depend on concentrations of cortisol, a hormone released in response to physical and psychological stress.
hormonal mechanisms - the role of testosterone
- STRENGTHS
P) support from Dabbs et al (1987)
E) higher TT levels in criminals with history of primarily violent crimes compared to non-violent
L) empirical evidence that TT levels cause differences in aggression
hormonal mechanisms - the role of testosterone
- LIMITATIONS
P) gender bias
E) most studies focused on males and ignored possibly different influence TT has on females
E) Eisenegger et al (2001): TT can make women act ‘nicer’ rather than aggressive
L) supports that rather than directly causing agg, TT promotes status seeking behaviour which increase dominance (agg only one type of this)
neural and hormonal mechanisms
- GENERAL EVALUATION
P) biologically reductionist
E) ignore evidence that agg may be learned through the environment
E) Banduras bobo doll experiment - children observed and imitated aggressive behaviour
L) limited; doesn’t account for environment and SLT plays part in agg
P) biologically deterministic
E) agg caused by internal factors eg limbic system, low serotonin, and high testosterone which we can’t consciously control
E) removes free will and choice over aggression
L) wrong for legal system to punish aggression if not responsible
- nature>nurture
- nomothetic
- socio-economic reasons
- scientific
