Aggression Flashcards
Outline the limbic systems role in aggression
The limbic system is a network of structures within the brain. One of its functions is to process emotional responses such as aggression. The first attempt to link limbic structures to emotional behaviours such as aggression was by Papez and later revised by Maclean
The amygdala has a key role in how an organism assesses and respond to environmental threats and challenges. The reactivity of the amygdala in humans has proven to be an important predictor of aggressive behaviour.
The hypothalamus is implicated in integrating and expressing emotional responses, such as the fight or flight response.
Give research support of the limbic system’s role in aggression
Gospic et al:
fMRI brain scans were used to measure brain activity during a game designed to provoke aggression. Researchers found when participants rejected an unfair monetary reward ( which can be seen as social provocation ) there was increased activity in the amygdala.
These spikes reduced in severity when participants prior to the game were given benzodiazepines. As these drugs reduce ANS arousal, this further suggests there is a correlation between amygdala activity (action of the ANS) and aggression.)
Egger and Flynn:
Found that when different areas of cats’ hypothalamus’ were electrically stimulated, they would show aggressive behaviour towards rats. This aggressive behaviour was then either suppressed or increased when different regions of the amygdala were stimulated.
Sumer et al
Describes a case study of a girl who suffered from epileptic fits and displayed aggressive behaviour. Brain scans revealed she had a tumour in her limbic system. Doctors treated the tumour with drugs, which stopped both the seizures and aggressive behaviours.
Evaluate the limbic system’s role in aggression
Whilst there is strong evidence to support a correlation between the role of the limbic system and aggression, alone, this could be an oversimplification of aggressive behaviour.
For example, the research from Coccaro et al suggests the limbic system works in tandem with the OFC. The OFC functions in the role of self control, impulse regulation and the inhibition of aggressive behaviour. Coccaro found in patients with psychotic disorders, prominently featuring aggressive symptoms, their OFC activity was reduced. This disruption to activity leads to reduced impulse control and thus increased aggression.
The regulation of aggression is highly complex and involves at least three neural structures in the brain: the amygdala, the OFC and the connection between the two.
Outline the role of serotonin within aggression
Serotonin is an inhibitory neurotransmitter and a mood regulator. When present in normal levels in the OFC, when the amygdala is stimulated, and sends aggressive impulses to the OFC, serotonin can inhibit these impulses preventing aggressive behaviour.
Therefore, lower concentrations of serotonin in the OFC may result in less self control and more acts of aggression as there is nothing to inhibit these aggressive impulses. This is known as the serotonin deficiency hypothesis.
Evaluate the role of serotonin in aggression
Research support:
Berman et al. conducted a study where participants given paroxetine, which increases serotonin activity, gave fewer and less intense electric shocks compared to those given a placebo, under similar provocation levels. However, this was only true of participants who had a prior history of aggression.
Yet this still provides strong evidence to suggest serotonin function and aggression are correlated.
Passamonti:
Used a technique called acute tryptophan depletion. The experimental group consumed a drink lacking in tryptophan whilst the control group consumed a drink which would not alter their tryptophan levels in the brain.
FMRI scans were used to measure the brain activity of participants when presented with images of either angry or neutral faces. When viewing the angry face, the scans showed a reduction in frontal lobe activity and communication between the frontal cortex and amygdala in the brains of participants in the experimental condition.
These participants also scored highly on an aggression questionnaire.
These results suggest that a lack of serotonin reduces the ability of the frontal cortex to to control aggressive impulses in the amygdala.
Data collected used objective methods and a double blind placebo reduced any biases, making the findings more reliable. However, the use of a questionnaire could be seen as an unreliable method of measuring aggression.
Outline the role of testosterone in aggression
Testosterone is an androgen responsible for the development of masculine features. It also has a role in regulating social behaviour via its influence on certain areas of the brain implicated in aggression.
T tends to be 8x higher in males than women which can attempt to explain why aggressive behaviour is much more commonly seen in men.
Higher T levels in the OFC, reduces the OFCs ability to regulate the aggression coming from the limbic system. With decreased executive function, an individual is more prone to aggressive outbursts. High levels of T also increase amygdala activity as well as act on serotonergic synapses, lowering serotonin levels and thus decreasing the inhibition of aggressive impulses coming from the limbic system.
Outline research into the role of testosterone within aggression
Wagner et al measured aggression in mice by seeing how frequently they bit a target. The male mice were shown to be much more aggressive than their female counterparts. However, this difference was removed after castration and once again came back after the male mice were injected with T. Similarly, the female mice bit the target more frequently after injections of T.
Dolan et al:
Showed that violent prisoners in
maximum security prisons displayed higher levels of testosterone than their non-violent counterparts.
Mehta and Robert Josephs
Measured changes in participants T levels before and after losing a competitive game. After their loss, participants were asked whether they wanted to challenge their victorious opponent to a rematch (the aggressive option) or or complete an unrelated task (non-aggressive).
73% or participants whose T levels rose chose to rematch compared to 22% of participants whose T levels decreased.
This suggests T may lead to dominance and status seeking behaviour and aggression is the way this behaviour is expressed. This suggestion supports Mazur BMoS.
Evidence of the link between testosterone and aggression in humans is mixed. Mehta and Josephs dual hypothesis demonstrates how high serotonin levels can result in the display of aggressive behaviour, but only when cortisol levels are low.
Evaluations to neural and hormonal explanations for aggression
High internal validity:
Studies use highly controlled measuring tools, such as fMRI scanners. Similarly, biological chemicals are carefully measured. These objective methods reduce any forms of potential bias and produce reliable findings.
Biologically reductionist:
The idea that someone’s aggressive behaviour is entirely down to their biological makeup could lead to effective biological interventions to reduce aggression. However, it is likely to be the full explanation for something so complex. Biology may explain emotional triggers but whether a person chooses to or not to act on these impulses depend on other social psychological factors.
Biologically deterministic:
Taking a biologically deterministic approach suggests that someone couldn’t act otherwise. This could have implications within society. For example, judges may use neural or testosterone abnormalities as mitigating factors for violent crime. Likewise, individuals may lose a sense of agency and feel as though they have no power to resist aggressive impulses.
Social sensitivity:
Research into the links between biological factors and aggression could have negative implications for the people used in the studies. For example, if abnormalities in the limbic system are shown to be a predictor of violent behaviour, this could lead to discrimination or suspicion of people with these abnormalities before they have even committed an offence.
Outline twin and adoption studies in relation to aggression
Coccaro et al
For aggressive behaviour defined as physical assault, the researchers found concordance rates of 50% for MZ twins and 19% for DZs.
Mednick and Hutchings:
There is limited research into aggression in adoption studies, however, their research found an association between criminality and genetics. When looking into the criminal records of Danish adoptees, 21.4% of those with a criminal record had a biologically criminal father, compared to 10.5% of those with a criminal record who did not.
Outline the role of MAOA gene in aggression
MAOA is an enzyme which breaks down neurotransmitters such as dopamine and serotonin. MAOA is regulated by the MAOA gene for which there are several variants of.
The MAOA-L gene has been associated with aggressive behaviour leads to low MAOA activity in areas of the brain and can lead to an excess of serotonin.
Outline research in the role of MAOA-L in aggression
Brunner et al studied 28 male members of a large Dutch family who were repeatedly involved in impulsive aggressive behaviours such as rape, attempted murder and physical assault. The researchers found that these men had abnormally low levels of MAOA in their brains and the low activity version of the MAOA gene. This suggests extreme aggression levels could have a genetic origin.
Stuart et al: studied 97 men who, because they had been involved in inflicting intimate partner violence (IPV), were part of a batterer treatment programme. Men with the low activity MAOA gene were found to be the most violent perpetrators of IPV. They engaged in the highest levels of physical and psychological aggression and inflicted the worst injuries on their partners.
Frazetto et al: found an association between higher levels of antisocial aggression and the MAOA-L gene variant in adult males, as expected.
But this was only the case in those who had experienced significant early trauma. Those who had not experienced such childhood trauma did not have particularly high levels of aggression as adults, even if they possessed MAOA-L. This is strong evidence of a gene environment interaction
Evaluate the role of MAOA-L in aggression
Contradictory theories:
MAOA-L reduces MAOA enzyme activity, leading to an excess build up of serotonin in the brain. However, previous studies have correlated with aggression with lower serotonin levels. This therefore suggests the role of serotonin is complex.
It is hard to isolate the role of genes from environmental influences. Genes may only create a vulnerability to aggression, when combined with certain environmental influences. Therefore, the genetic explanation of aggression seems not to be a complete one. McDermott et al. showed that participants with MAOA-L behaved aggressively in laboratory-based money allocation games, but only when they were provoked, otherwise, they were no more aggressive than other participants.
Issues of measuring aggression:
Methods of measuring aggression differ between studies, and include self reports, parent and teacher reports and direct observations. Eg: Rhee and Waldman’s meta analysis of 51 twin and adoption studies found that genetic factors had a greater influence on aggression in studies using self reports rather than parent and teacher reports. This makes it harder to draw valid conclusions about the role of genetics in aggression when there is inconsistency with how aggression is being measured.
Genetics can not account for all the variance in aggression. For example, a third of Western men possess the warrior gene, yet not all of these men are aggressive. This therefore indicates there may be social factors at play.
Outline ethological explanations for aggression
The ethological explanation proposes that aggression can be the result of an evolved automatic biological response in the brain and suggest that the main function of aggression is adaptive; it helped the species survive and successfully reproduce.
Outline ritualistic aggression
Lorenz noted when observing fights between animals of the same species there was little actual physical damage.
Most aggressive encounters consisted mainly of a period of ritualistic signalling eg: baring of teeth/growling. Following this, intra species aggressive confrontations would end with ritual appeasement displays. These indicate acceptance of defeat and inhibit aggressive behaviour in the victor, preventing any damage to the loser. Eg: wolves assuming a submissive position.
This appeasement display would allow a victor to be established without causing the death of the loser. This is adaptive because if every aggressive encounter ended with the death of one of the combatants, that could threaten the existence of the species.
Outline the role of fixed action patterns in aggression.
An innate releasing mechanism is thought to be a neural structure and is a response to a specific stimulus within the environment: This process is instinctive and results in a predictable behavioural sequence, known as a fixed action pattern.
FAP’s tend to be:
An unchanging sequence of behaviour
The same for every animal of that species
Unaffected by learning
Cannot be altered before completion (‘ballistic’)
Only occurs in a specific situation
Response to a specific stimulus
