Neural and Hormonal Mechanisms in Aggression Flashcards
What do biological explanations assume?
The potential for aggression is located within an individuals biological makeup
What are neurotransmitters?
Chemical substances that enable impulses to travel from one area to another
How does serotonin influence aggression?
- Can inhibit responses to emotional stimuli so reduce aggression
- Low levels are associated with increased susceptibility to impulsive, aggressive, violent and suicidal behaviours
What did Mann do in his study into serotonin?
- 35 p’s given dexfemfluramine to reduce serotonin
- Questionnaire to assess hostility and aggression given after
What did Mann find in his serotonin study?
Drug was associated with an increase in hostility and aggression scores, providing support for a link between low serotonin levels and increased aggression
What is a limitation of Mann’s study into serotonin?
- Self report methods may lower reliability due to SDB
- People want to paint themselves in the best light
What is a second methodological limitation of Mann’s study?
- Only conducted on men - shows beta bias
- May not be valid to women
- May encourage stereotypical beliefs about female aggression and an andocentric view of human behaviour
What can we conclude from Mann’s study after taking methodological flaws into account?
- While this study provides some support for the S/A link
- Lack of generalisability may limit it’s use in supporting the link as results may not be valid to wider population
Where does further support for the serotonin and aggression link?
Non-human studies - Raleigh
What did Raleigh’s study involve?
- Half a group of monkeys fed diet high in tryptophan to increase serotonin
- Half fed diets low in tryptophan to decrease serotonin
What did Raleigh’s study show?
Low serotonin - increase aggression, providing considerable research support for the role of neurotransmitters
However, what are 2 criticisms of Raleighs study?
- May lack generalisability as we cannot apply to humans. Animals have different anatomy and their behaviour is a poor predictor of human behaviour, limiting the support we can gain.
- However may offer us an expanded insight into physiological and psychological processes
- Ethical concerns - could cause pain and suffering, lacking credibility outside the study
What did Bond find?
Evidence to support the idea that neurotransmitters can influence aggression from antidepressants
What were Bond’s findings in clinical studies of antidepressants?
Antidepressants that increased serotonin were found to reduce irritability and impulsive aggressiveness
How can dopamine lead to aggressive behaviour?
Increases in dopamine via amphetamines have been associated with increases in agg, whereas antipsychotics to reduce dopamine reduce aggressive behaviour
Who does evidence for dopamine link come from?
Couppis and Kennedy
What did Couppis and Kennedy find?
Mice - reward pathway in brain becomes engaged in response to aggressive event - Dopamine acts as a positive reinforcer following an aggressive act as it causes feelings of euphoria
Why might dopamine acting as a reinforcer cause aggressive behaviour?
Suggests individuals may intentionally seek out an aggressive encounter for the rewarding sensation
Why do Couppis and Kennedys findings provide conflicting evidence?
- Provides support for idea that dopamine is linked
- As a cause rather than a consequence as initially suggested
- Need for further research?
What did a meta analysis of 29 studies involving antisocial children and adults find?
- Low serotonin found in aggressive individuals but no difference in dopamine
- Reduce serotonin found in all antisocial groups but particularly suicide attempters
- Suggests that serotonin depletion leads to impulsive behaviour which can result in aggression in various forms
What does the meta analysis of 29 studies show?
- Biological, deterministic approach in explaining aggression
- Serotonin levels are a predictor of future behaviour
What hormonal mechanism is thought to explain aggressive behaviour?
Male sex hormone Testosterone
When and why does testosterone influence aggression?
Influence aggression from young adulthood onwards due to its action on brain areas involved in controlling aggression
Who tested the testosterone/aggression hypotheses?
Dabbs in a study measuring salivary testosterone levels in violent and non violent criminals
What did Dabbs find in his testosterone study?
Highest testosterone levels found in those with a history of primarily violent crimes
However, what could be argued as a result of Dabbs findings?
Lack of generalisability as research was conducted only on criminals. However, this was responded to by studies of non-prison population, finding similar results and so giving credit to original findings
What is the challenge hypothesis?
Monogamus species: testosterone levels should rise only in response to social challenges like threat to status, partner or male-male aggression. Humans are M so we would expect the same findings
What approach does the challenge hypothesis link to?
Evolutionary approach, as it suggests we are biologically adapted so our T levels rise only to conditions of threat in order to provide defence
Which further studies provide further evidence for the challenge hypothesis and so add credibility to hormonal explanations as they can be applied to the real world?
- Gun related crimes can be explained by testosterone increase by the presence of stimulus, as this is seen as a threat
- Klinesmith: Child saliva measurements for testosterone post play with gun or childs toy. Gun - significant testosterone increase
However, Klinesmith’s study may be limited because..
Conducted on male students so many not be valid to the general population e.g females and different ages
There has been inconsistent evidence from research into testosterone…
Archer - meta analysis of 250 males in 5 studies. Weak positive correlation was found.
- May be accredited to different measurements used over the studies (small samples, only men, etc) so show beta bias
- Concluded that due to methodological issues, a correlation of 0.8 was more appropriate providing modest support
What is Cortisol?
Another hormonal mechanism that may influence aggressive behaviour
What does cortisol do?
Increases anxiety and likelihood of social withdrawal, thus has a mediating effect on other aggression related hormones such as testosterone
What do low/high levels of cortisol do?
High levels inhibit testosterone which leads to aggression. Low levels are found in habitual violent offenders and school children.
What do levels of cortisol suggest?
- Although T is primary hormonal influence
- Low cortisol also plays a role by increasing the likelihood
Evidence for the role of Cortisol comes from McBurnett on boys with behavioural problems..
Consistently low levels of cortisol boys began antisocial acts at a younger age and show 3x the number of aggressive symptoms than those with high or fluctuating levels
The neural and hormonal mechanisms explanation follow a biological approach. What is a strength of this?
Such approaches allow for empirical data, easy to gather strong scientific evidence such as saliva samples, validating the theory as an explanation
The neural and hormonal mechanisms explanation follow a biological approach. What is a limitation of this?
Reductionist - does not take factors such as social influencing factors into account
