Aggression

Biological models of aggression

Assume that aggression is located within the biological makeup of the individual rather than in the environment around them

AO1 Limbic systen

• Set of subcortical brain structures in the brain and us thought to be closely linked with regulating emotional behaviour.

• Limbic system has connections to the pre-frontal cortex, which is involved in the anticipation of awards.

• The Amygdala us responsible for attaching emotional significance to sensory information. Important in how we assess and respond to environmental threats

• The hypothalamus is responsible for the regulation of the autonomic nervous system, which in turn regulates emotional responses.

• The PFC is crucial for regulating social behaviour and aggressive responses. Damage to the PFC would reduce inhibition of the amygdala resulting in higher levels of aggression.

• The limbic system responds to environmental threats and challenges, known as reactive aggression.

AO3 Limbic system in Aggression - 16 marker order

(+) Research to suggest that the amygdala is important in aggression comes from research using sustained electrical stimulation of the Amygdala. Le Doux found that electrical stimulation to the amygdala in lab animals led to fear and rage responses. This suggests that the amygdala must be linked to aggression, therefore supporting the role of the limbic system in aggression.

(-) Animal research - issues with extrapolation so can we be sure this is how the amygdala affects aggression in humans.

(+) But we do have some human research to support the role of amygdala in aggression. Narabayashi reported that 43/51 patients who received operations to destroy their amygdala showed more normal social behaviour afterwards including reduced aggression.

(-) But this research lacks the ability to establish cause and effect = there was no control group, we were unable to study these people before their surgery so there is a limit to the extent we can use this research to support the role of the limbic system in aggression.

(-) Socially sensitive - people with tumours or issues with their amygdala might be treated differently because their expected to be hyper aggressive. e.g not allowed certain jobs even if they aren’t particuarly aggressive.

AO1 Role of serotonin

• A neurotransmitter involved in the communication of impulses between neurones.

• Works on the frontal areas of the brain to reduce generation of impulses in the amygdala which controls fear, anger and other emotional responses.

• Therefore serotonin has a calming influence and can increase behavioural control.

• Low levels of serotonin means difficulty controlling impulsivity and therefore more aggressive behaviour

AO3 role of serotonin in aggression

(+) Raleigh studied vervet monkeys and found that individuals fed on experimental diets high in tryptophan - which increases serotonin levels - exhibited decreased levels of aggression. Individuals fed on low tryptophan diets exhibited increased aggressive behaviour.

(-) However, evidence for the role of serotonin is mixed. Huber found that increasing levels of serotonin in crayfish increased the length of time they continued fighting for. Crayfish who’s serotonin levels were increased continued to fight beyind the point at which they would usually stop. This suggests that the level of aggression was due to increased levels of serotonin. Despite contradictory evidence it still suggests that serotonin plays a role in aggression.

(-) Both use animal research which has issues with extrapolation to humans. Therefore we are unsure on serotonins affect on human aggression. Overall, more evidence into the role of serotonin in aggression is needed.

Additional evaluation for neural mechanism

(-) Ethical constraints - difficult to link experimentally to humans. unethical to reduce or increase levels of serotonin in humans. all research is only correlational.

(-) therefore cause and effect cannot be established. Therefore other factors may be responsible for aggressive behaviour for example environmental triggers and learned responses. There fore research can only give an indication of a vulnerability to aggression.

(-) Reductionist/Deterministic/Nature

(-) other approaches - SLT

Hormonal mechanisms

A Hormone can be defined as a chemical substance produced by the endocrine glands and regulates the activity of certain cells and organs

AO1 The role of testosterone

• Aggression occurs more often in males than females.

• The sex difference is often attributed to the effect of the male sex hormone testosterone.

• Class of hormones called androgens - important in producing sperm and developing sexual characteristics

• These hormones exert an influence on a range of behaviours including aggression.

• High levels of aggression from a very young age have been found to increase the likelihood of aggression behaviour.

• High levels of testosterone can reduce activity in the OFC, meaning there could be a heightened emotionally aggressive response

AO3 Role of testosterone in aggression

(+) Dabbs investigated the relationship between testosterone, crime and prison behaviour. Those who had committed sexual and violent crimes had the highest levels of testosterone. they were also more likely to be confrontational prisoners. This suggests there is a positive correlation between testosterone and aggressive violent crimes, and therefore a valid explanation for aggressive behaviour in the real world.

(-) There is no predictive validity between testosterone levels and aggression. For example someone who is aggressive will have high levels of testosterone as a result, carrying out aggressive acts causes increased levels of testosterone not the other way around. This highlights the importance of other factors such as environmental triggers and implies hormones do not determine aggressive behaviour but are the result of aggression themselves.

(-) All human research is correlational therefore we cannot infer causation between aggression and testosterone as a hidden third variable such as modelling behaviour from an aggressive model could be the cause of aggression not testosterone

Genetic explanations

Family/Twin/Adoption studies

MAOA gene

AO1 Family/Twin/Adoption studies

Suggests that aggression is inherited MZ twins share 100% of genes but DZ twins only share 50%. so we would expect greater similarities in MZ twins if aggression is mostly genetic.

For physical aggression researchers found concordance rates of 50% for MZ twins and 19% for DZ twins. for verbal aggression MZ twins were at 28% were DZ twins were at 7%. Concordance rates are higher in MZ twins suggesting a genetic component in aggression.

AO3 Twin studies

The Equal Environment assumption - MZ twins are raised in very similar environments so it is difficult to distinguish between environment and genetic factors in aggression. If genetic were the sole cause of aggression concordance rates would be 100%. Any less suggests an environmental influence. This provides problems for the genetic argument in explaining aggression.

AO1 MAOA Gene

MAOA gene codes for the MAO-A enzyme

This enzyme breakdowns neurotransmitters after synaptic transmission, helping to clear out additional unwanted synaptic transmissions.

It breaks down neurotransmitters such as serotonin and dopamine

A mutation of the MAOA gene can lead to abnormal activity of the MAO-A enzyme, which then affects levels of serotonin.

Low levels have been associated with impulsive aggressive behaviour.

MAOA-L is the low activity variant of the MAOA gene called the ‘Warrior Gene’

AO3 MAOA Gene Essay structure

(+) Cases mice study
Disabled the MAOA gene in the X chromosome of mice and found that without the MAOA enzyme, levels of dopamine and serotonin increased and males became highly aggressive. Females were unaffected. Restoring the function of the gene returned the male mice to a normal state. This suggests that the prescence of the mutated MAOA-L gene increases aggression, therefore support the genetic explanation of aggression.

(-) Issues with extrapolation.
research used animals can animal research be extrapolated to comples human aggression - verbal, physical, reactive, pre-mediated.

(+) However, we do have human research from Bruner.
Who discovered a defective MAOA gene in a Dutch family with a history of male violence. 28 male members were involved in violent crimes (rape, murder, GBH). All these men had the low activity version of the MAOA gene. This supports the MAOA genetic explanation, as it suggests that the prescence of the MAOA-L gene can affect human levels of aggression.

(-) Biologically Reductionist
The genetic explanation for aggression is biologically reductionist - reducing complex human aggression into a single component part in this case a single gene mutation. Other theories suggest that complex social factors may be more important. E.g the social learning theory of aggression which suggests…
This suggests the role of genes might have been overestimated.

(+)Therefore, perhaps the diathesis-stress model is a better explanation than genetics alone. This is the idea that a person may carry the gene for aggression, however, it takes an environmental trigger to activate this aggression. Moffit preformed a longitudinal study on 442 new zealand males. He recorded which participants had suffered from abuse and what level of activity of the MAOA gene the ps had. Those who has suffered abuse and had the low variant of the MAOA gene were nine times more likely to indulge in aggressive behaviour. This suggests that the MAOA gene is involved in aggression, but is sensitive to social experience in early development.

AO1 Ethological explanation of Aggression

ONLY USE TO EXPLAIN ANIMAL AGGRESSION NOT HUMAN

Ethological explanations suggest that aggression is adaptive to aid survival.
- it reduced competition for resources, food, and territory.
- It establishes dominance hierarchies. which gives the dominant male mating rights.

Ritualistic aggression

A series of behaviours carried out in a set order.
Lorenz found that most intra-species aggression consisted mostly of ritualistic signalling rather than physical. E.g A wolf will expose its neck to the victor of a fight for dominance, deliberately making itself vulnerable to signal defeat. This is adaptive because if every aggressive encounter ended in death, it could threaten the existence of the species

Innate releasing Mechanisms
A built in physiological process or structure. It acts as a filter to identify threatening stimuli. An environmental stimulus activates the IRM and it triggers a fixed action pattern of behaviour.

Fixed action patterns
A specific sequence of behaviour triggered by the IRM.
Unchanging sequence of behaviour
Universal and species specific
Unaffected by learning
Ballistic - once triggered must be completed
Single purpose - occurs in specific situations

AO3 or AO1 Tingenberg’s research

The male stickleback fish establish territory around a nest for females, any other male stickleback who enters their territory is met with aggressive attacks. Male sticklebacks have a red underbelly.

Tingenberg presented male sticklebacks with a series of wooden models in different shapes. The models had red underbellies to simulate a male stickleback.

All male sticklebacks attacked the models with red underbellies. No red underbelly meant no aggression. Tingenberg found that the Fixed action pattern did not change from one encounter to another - once triggered it always ran its course to completion. This shows that behaviour is invariant and therefore is a strong argument for aggressive behaviour being innate

AO1 Frustration - Aggression Hypothesis

A Theory based on the psychodynamic approach and argues that aggression is a drive.

Suggests that aggression is a consequence of feeling of frustration

Frustration is the feeling you experience when you are trying to achieve something and there are barriers preventing you from achieving your goal

Frustration leads to aggressive behaviour as a means to relieve the built-up tension, it is cathartic.

factors that can affect the likelihood of aggression are - Proximity to the goal / wether the aggression will remove the barrier / aggressive cues.

The hypothesis also recognises that that aggression is not always expressed directly against the source of frustration - either the cause of frustration is abstract / too powerful / unavailable.

AO3 Frustration - Aggression Hypothesis

(+) Harris conducted a field experiment on wether proximity to the goal had an effect on the level of aggression shown. She used situations where cues occurred such as shops and her confederates pushed in front of people. If ps were closer to the front of the queue ps were more likely to act in an aggressive way than if they were at the back. This supports the idea of proximity to achieving the goal causing heightened frustration leading to aggressive responses. Confirming the role of frustration in aggression.

(+) Harris’s study was a field experiment, and therefore has high ecological validity. She used real life deceived participants in a natural setting, the task measure also had mundane realism with the act of pushing in front of people as a real life experience. This enhances the generalisability of the findings to real-world situations.

(-) However, aggression is not always prompted by frustration. For example, premeditated and planned aggressive acts of psychopaths and killers are not usually underpinned by frustration. This suggests that there are other elements to aggressive behaviour, therefore the frustration - aggression hypothesis might be considered reductionist breaking down aggressive behaviour into simple components- one emotion of frustration. Therefore this limits the extent to which we can consider the frustration-aggression hypothesis as a full explanation for aggression as it cannot explain all frustration.

(-) Furthermore, a limitation is that is that not everyone who experiences frustration reacts with aggression. It is possible that some may cry or not feel anger rather than become aggressive. This suggests there may be other factors that play a role in aggression. For example biological explanations suggest that hormones such as testosterone and serotonin can cause aggressive behaviour. Perhaps an interactionist approach may be more applicable, suggesting that a biological predisposition paired with a environmental trigger may cause aggressive behaviour.

AO1 - Evolutionary explanations of Human Aggression

Argues aggression is an innate behaviour. It is adaptive and evolutionary. Occurs through genetic mutation.

Aggression is a behaviour which promotes individual survival and reproductive success.

Aggression can be explained as there was competition for resources. Aggressive individuals are more able to compete for food and mates and therefore reproduce more successfully.

Aggressive genes are then passed onto future generations

Aggression can be seen in behaviours that display sexual jealousy - male violence against partners motivated by jealousy and to ensure own paternity and genetic success (Fear of cuckoldry)

Aggression can also be explained through male retentive strategies. Direct guarding/ negative inducements (threats)

AO1 Evolutionary Aggression Bullying

Powerful individual uses aggression deliberately and repeatedly against a weaker person.

Evolutionary explanations would suggest ancestors could have used bullying as an adaptive strategy to increase chances of survival by promoting their own health and creating opporturnities for reproduction.

Male Bullying Volk et al - bullying behaviour to attract females - dominance acquisition of resources and strength. Ward off potential rivals. Benefits those at the top of the dominance hierachy.

Female Bullying - Takes place within a relationship as a method to control a partner. To secure their partners fidelity, and their continued supply of resources.

AO3 Evolutionary explanations of human aggression

(+) Research support from Wilson for mate retention strategies. women who reported mate retention strategies in their partners were twice as likely to have suffered from physical violence at the hands of their partners. This suggests that aggressive behaviour can be explained by mate retention strategies. Male violence can therefore be explained by sexual jealousy as a way to ensure paternity and genetic success.

(+) Therefore this research has useful implications as it could be used to indicate a risk of potential violence. relationship counselling can therefore be used before situation escalates. It would also be informative to investigate whether women’s mate retention strategies is also linked to partner directed violence.

(-) However, in some cultures males are required to act violently in order to gain status, whilst in others aggression leads to a damaged reputation. E.g the Yanomamo tribe require violence for status, whereas the kungsan tribe are non-aggressive despite the risk of infidelity. This therefore provides a problem for the evolutionary explanation, other explanations may be better at explaining such cultural differences for example SLT.

(-) Evolutionary explanations are retrospective. They are based on observing behaviour and then proposing a survival function to account for it. While the evolutionary explanation is plausible it is unfalisifable and any theory deemed to be scientific should be able to be falsified. This therefore detracts from its strength as an explanation of aggression as it is less scientifically credible.

(-) Holtzworth - Monroe pointed out the fact that there are huge individual differences in whether an individual will respond to jealousy/infidelity with aggression. He argues that violent males may lack effective ways of mediating and responding to situations of jealousy compared to non-violent males, and therefore the evolutionary approach is deterministic as it does not account for the fact that most people are able to demonstrate free will to respond non-violently despite our ‘evolutionary’ urges.

AO1 Social learning theory of Aggression

Bandura argued that