Dopamine:
-Neurotransmitter which mediates pleasure and excitement along the mesolimbic pathway.
-Lavaine: Found that an increase in Dopamine levels through use of amphetamines is associated with aggression. Suggests that higher levels of dopamine correlates with high levels of aggression.
-Studies found that when participants given amphetamines, which increase dopamine there is an increased level of aggression.
Serotonin:
-Important for social decision making by restraining aggressive social responses. It prevents stimulation of the Amygdala. Serotonin is the happy neurotransmitter, low levels of it has less restraint on the Amygdala & when it’s more active it leads to aggression.
-Man et al: Gave participants drug Dexfenfluramine which lowers serotonin. Researcher gave a questionnaire to assess aggression levels which raised in males but not females.
-Popova et al: Found dogs that selectively bred for docile and domestication treatments have an increase of Serotonin. Suggests link between Low serotonin & aggression.
-In clinical studies the use of anti-depressant drugs elevate Serotonin levels reducing aggression.
| Strength | Weakness |
| Man – Gave ppt drug Dexfenfluramine which lowers serotonin. Researcher gave a questionnaire to assess aggression levels which raised in males but not females. – show NT have role in aggression.
Lavaine: Found that an increase in DA levels through use of amphetamines is associated with aggression – Suggests that higher levels of DA correlates with high levels of aggression. Popova- Found dogs that selectively bred for docile and domestication treatments have an increase of Serotonin. – suggests link between Low serotonin & aggression. Application – links between serotonin & DA have been made with increase aggression – showing importance of understanding DA & serotonin using bio treatment to reduce aggression. |
Validity – Man assessed Validity by using questionnaires to see how hostile & aggressive ppts were – data subjective to social desirability
Generalisability – study used selective bred dogs for docile & domestication temperaments – cannot apply animal studies to humans as our bodies respond differently to NT Social learning theory – suggests that aggressive behaviour is from watching role models performing such behaviour and individual imitating – looks at nurture aspects of aggression which theory ignores. Validity – difficult to establish link between NT & aggression as it’s not clear aggression arises due to low serotonin & high DA – cannot state that NT causes aggression. Reductionist – link between NT & aggression is insufficient on their own in explaining complexity of human aggression – more holistic theory needed |
Role of Hormones in Aggression – Hormones
Chemical messengers which travel in the blood stream at a slower rate but can effect mood, metabolism and sexual reproduction. Hormones work by binding to receptors & changing their functions which cells respond to in particular ways.
Testosterone:
Men are more aggressive as a result of Testosterone as they create more of it and are greater exposed to it in the womb. Raine found 5% men could be characterised by pattern of anti-social behaviour & likely to commit 50%-70% of violent crimes.
-Harlow – Young male Rehus monkeys engage in more rough play then their sisters. Links to human boys as they more aggressive than girls. Males engage in more crime than females, involvement usually arises in early teens when testosterone rises.
-Kalat- In 15-25 year old men, those with highest levels of circulating testosterone show highest levels of aggression measures by crime stats.
-Dabbs – measures levels of testosterone in saliva of 89 male prisoners involved in violent & non-violent crimes. 10/11 violent prisoners had high levels of testosterone. Higher than non-violent criminals.
-Castrated male rodents compared to control group under conditions of threat & competition for mate. Castrated rodents showed little or no aggression but if injected with testosterone they become aggressive.
Adrenaline & Noradrenaline:
Released from adrenaline gland for fight or flight response.
-Kruk found a positive correlation between adrenaline hormones, cortisol hormones and aggression suggesting intense exposure to stress (SITTING A-LEVEL PSYCHOLOGY) can lead to aggressive behaviour.
Cortisol:
Is a steroid hormone produced by adrenaline gland & released in response to stress and low blood glucose.
-Burzman Et al: Recruited 17 boys in psychiatric hospital age 7-9 years old. Looking to see if they could find Cortisol in saliva relating to aggression. In first 24 hours Saliva samples taken 3 times a day: Waking, 30 minutes after waking and around 3:45-7:45.
Twice a day nurses rated aggressive behaviour.
Findings show amount of cortisol in Saliva 30 minutes after waking correlated to number of aggressive acts that day.
| Strengths | Weaknesses |
| Kruk – found a + correlation between adrenaline hormones, cortisol hormones and aggression suggesting intense exposure to stress can lead to aggressive behaviour. – long lasting adrenaline can cause aggression
Kalat- In 15-25 year old men, those with highest levels of circulating testosterone show highest levels of aggression measures by crime stats. – correlates link between aggression & testosterone Application – correlations found links between testosterone, adrenaline & cortisol with aggression – we need to understand role of hormones to develop bio or counselling treatment for aggression Reliability – both human & animal studies found links between testosterone & aggression – giving scientific creditability to findings as they been replicated with different samples. |
Correlations –correlation such as Kruk looking at cortisol, adrenaline & aggression. Cannot say one variables = the other & may be an unkown variable – cannot determine cause & effect
Social learning theory –aggressive behaviour is from watching role models performing behaviour and individual imitating – looks at nurture aspects of aggression which theory ignores. Lack of creditability – relationship between testosterone & aggression measured by blood or saliva but most accurate would be lumber puncture – isn’t done for researcher purposes so measure may lack creditability Reductionist – theories of aggression seperated into roles of brain, NT & hormones –research should take more holistic views acknowledges complexity of human aggression & interrelation of these factors. |