AGGRESSION EXAM REVISON -
NEURAL AND HORMONAL MECHANISIMS IN AGRESSION -
NEURAL MECHANISMS IN AGGRESSION -
THE LIMBIC SYSTEM -
Papaz and Mclean linked the limbic system to emotional behaviours, including aggression, they defined the system as the hypothalamus, amygdala and parts of the hippocampus
the reactivity of the amygdala in humans and other mammals is an important predictor of aggressive behaviour (IE the more responsive the amygdala, the more aggressive the person is) so the amygdala has a key role in how mammals assess and respond to environmental threats
this amygdala activity is illustrated in a study by Gospic et al where some participants were subjected to mild provocation, when participants reacted aggressively, fMRI scans showed a fast and heightened response by the amygdala
when a benzodiazepine drug (which reduces arousal of the autonomic nervous system) was taken before the provocation led to two results, it decreased the activity of the amygdala and halved the number of reactions (IE reduced aggressive responses) which illustrates again the role of the amygdala in aggression
ORBITALFRONTAL CORTEX AND SEROTONIN -
serotonin is a neurotransmitter that has a widespread inhibitory effect on the brain (it slows down and calms neurone activity)
normal levels of serotonin in the orbitofrontal cortex (OFC) are linked with reduced firing of neurons which in turn is associated with greater behavioural self control
decreased serotonin disrupts this mechanism, which reduces self control leading to an increase in impulsive behaviour including aggression
Virkkunen et al compared levels of a serotonin breakdown product in the cerebrospinal fluid of violent impulsive and violent non-impulsive offenders, the levels were significantly lower in the impulsive offenders
EVALUATION -
OTHER BRAIN STRUCTURES -
more recent research showing that non-limbic brain structures are also involved in aggression, limbic structures function together with the orbitofrontal cortex which ismt part of the limbic system
the OFC is involved in impulse regulation and inhibition of aggressive behaviour, according to coccaro et al, OFC activity is reduced in psychiatric disorders that feature aggression
which shows that the neural regulation of aggression is more complex than theories focusing on the amygdala suggest
DRUGS AND SEROTONIN -
research into the effects of drugs such as paroxetine that increase serotonin have been found to also reduce levels of aggressive behaviour
berman et al gave participants either a placebo or a dose of paroxetine, they then took part in a lab based game that involved giving and receiving electric shocks in response to provocation
the paroxetine group consistently gave fewer and less intense shocks than the placebo group, this is evidence for a causal link between the function of serotonin and aggression
HORMONAL MECHANISMS IN AGGRESSION -
TESTOSTERONE -
the male sex hormone is testosterone, its an androgen responsible for the development of masculine features and is thought to be linked to aggression for several reasons
many people have observed that men are normally more aggressive than women, they become more aggressive towards other men at a time in development when testosterone levels are highest
testosterone has a role in regulating social behaviour via its influence on certain areas of the brain implicated in aggression
castration studies of animals show that removing the testes reduces aggression in the males of many species, giving injections of testosterone to the same animals restores aggressive behaviour
some evidence for a similar association in humans come from studies of prison populations, for example, violent offenders, dolan et al found a positive correlation between testosterone levels and aggressive behaviours in a sample of 60 male offenders in UK maximum security hospitals, these men had personality disorders such as psychopathy and histories of impulsively violent behaviour
PROGESTERONE -
there is some evidence that progesterone, a female ovarian hormone plays an important role in aggression in women, levels of progesterone vary during the ovulation cycle and are lowest during and just after menstruation
Ziomkiewicz found a negative correlation between progesterone levels and self reported aggression, which suggests low levels of progesterone are linked to increased aggression in women
EVALUATION -
ANIMAL RESEARCH -
non-human animal studies support the hormonal explanation of aggression, Glammanco et al reviewed studies that confirmed the role of testosterone, for example in a study on male rhesus monkeys there is an increase in both testosterone and aggressive behaviour in mating season
in rats, castration of males reduces testosterone and mouse-killing behaviour, and injecting female rats with testosterone increases mouse-killing behaviour, both these studies show the role of testosterone in a range of species
DUAL-HORMONE HYPOTHESIS -
however there is mixed evidence of the link between testosterone and aggression in humans, Carre and Mehta developed a dual hormone hypothesis to explain why, they claim that high levels of testosterone lead to aggressive behaviour, but only when cortisol levels are low
when cortisol is high, testosterones influence on aggression is blocked, cortisol plays a central role in the bodies response to chronic stress, which means the combined activity of cortisol and testosterone may be a better predictor of aggression rather than either hormone alone
GENETIC FACTORS IN AGGRESSION -
TWIN STUDIES -
several twin studies have suggested that heritability accounts for 50% of the variance in aggressive behaviour, for example coccaro et al studied men who were either monozygotic or dizygotic twins, because MZ twins share 100% of the same DNA, where as DZ twins only share 50% on average, we would expect to find greater similarities in aggressive behaviour between MZ twins if aggression is mostly influenced by genetic factors
this is because both MZ and DZ twins are raised together in the same environment, but MZ twins have a greater degree of genetic similarity than DZ twins
for aggressive behaviour defined as the direct physical assault, the researchers found concordance rates of 50% for MZ twins and 19% of DZ twins, the corresponding figures for verbal aggression were 28% for MZ twins and 7% of DZ twins
ADOPTION STUDIES -
similarities in aggressive behaviour between an adopted child and their biological parents suggest that genetic influences are operating, whereas similarities between an adopted child and their adoptive parents suggest that environmental influences are operating
Rhee and Waldman carried out a meta analysis of adoption studies of direct aggression and antisocial behaviour, a prominent feature of which is aggressive behaviour, they found that genetic influences accounted for 41% of the variance in aggression, more or less in line with findings from twin studies
THE MAOA GENE -
the MAOA gene controls the production of an enzyme called monoamine oxidase A, which regulates the neurotransmitter serotonin
the gene comes in different variants, high and low, the low-activity variant results in low activity of the MAOA enzyme, its this low activity which has been linked to aggressive behaviour
its nicknamed the warrior gene because of the research by Lea and Chambers , which showed the MAOA low variant was possessed by 56% of New Zealand Mauri men, compared to 34% of Caucasians
the link between the MAOA-L gene was further linked to aggression by the study done by Brunner on 28 men from a large Dutch family who were repeatedly involved is impulsively aggressive and violent behaviours such as rape, attempted murder and physical assault, these men has abnormally low levels of the MAOA enzyme variant
GENE X ENVIRONMENT INTERACTIONS -
genes are crucial influences on aggressive behaviour but they dont function in isolation, it appears to be the case that the MAOA-L gene activity is only linked to adult aggression when combined with early traumatic life experiences
for example Frazzetto found an association between higher levels of antisocial aggression and the MAOA-L gene variant in men, as expected, but this was only the case in those who had experienced significant trauma, such as physical or sexual assault before the age of 15
those who hadnt experienced such childhood trauma did not have particularly high levels of aggression as adults, even if they possessed the MAOA-L variant, which is strong evidence for gene-environment interaction, also known as a diathesis stress model
EVALUATION -
RESEARCH SUPPORT -
evidence suggests that the MAOA-L variant results in increased aggression, for example Brunner, or Lea and Chambers, however Mertins et al found that the converse is also true
in the study, men with the MAOA-L and MAOA-H variants of the gene took part in a money distributing game, men with the MAOA-H gene were more cooperative and made fewer aggressive moves than the low activity gene participants which supports the relationship between MAOA gene activity and aggression
COMPLEX LINK -
however the mechanism behind the MAOA-serotonin-aggression link is unclear, as in the neural mechanism of aggression it is low levels of serotonin thats thought to cause aggression due to the lessened inhibitory effect
however if its the MAOA-L gene which causes low activity of the MAOA enzyme then serotonin levels should be high as its not broken down, leaving for more inhibitory synaptic transmission, this shows that the relationship between the MAOA gene, serotonin and aggression is not yet fully understood
PROBLEMS WITH TWIN STUDIES -
twins studies which have been used as evidence for the genetic influence in aggression may lack validity, as in every pair of twins, they share the same environment as they are raised together
however DZ twins may not share the same environments to the same extent that MZ twins do, we assume they do, which is called the equal environments assumption
but this assumption maybe wrong as one aspect of twins environments is how they are treated by other people, MZ twins are treated very similarly, especially by their parents, however this isnt necessarily done to the same extent for DZ twins, which means that concordance rates may be inflated and that the genetic influences on aggression may not be as great as twin studies suggest
THE ETHOLOGICAL EXPLANATION OF AGGRESSION -
ADAPTIVE FUNCTIONS OF AGGRESSION -
the ethological explanation suggests that the main function of aggression is adaptive, aggression is beneficial to survival because a defeated animal is rarely killed, but is rather forced to establish territory elsewhere
this means that members of the same species are forced to spread out over a wider area and find resources in a different place which reduces competition pressure and the possibility of starvation
another adaptive function of aggression is to establish dominance hierarchies, EG male chimpanzees use aggression to climb their troops social hierarchy, which gives them a special status and more resources and mate opportunities
this happens in humans to, Pettit et al studied groups of young children and observed how aggression played an important role in the development of dominance hierarchies, this would be adaptive, and so naturally selected because dominance over others can bring a survival advantage
RITUALISTIC AGGRESSION -
a ritual is a series of behaviours carried out in a set order, lorenz observed that fights between animals of the same species produced little actual damage and most encounters consisted of a prolonged period of ritualistic signalling, EG displaying claws and teeth and facial expressions
lorenz also suggested that in intra species aggression, the ritualistic period ends with appeasement displays which indicate acceptant of defeat and inhibits further aggressive confrontations, for example an animal may display the side of their neck where the jugular vein is located, as a single bit here could be fatal
this is adaptive, as if every aggressive encounter ended in a death it could threaten the existence of a species
INNATE RELEASING MECHANISMS AND FIXED ACTION PATTERNS -
an innate releasing mechanism (IRM) is an inbuilt physiological process or structure, for instance a network of neurones in the brain
an environmental such as a facial expression, triggers the IRM which then releases a specific sequence of behaviours, this is called a fixed action pattern (FAP), according to Lea FAPs have six main features -
stereotyped and relatively unchanging
universal, the same for all individuals in a species
unaffected by learning, the same regardless of experience
ballistic, once tiggered, performed to completion without being altered
single purpose, it only occurs in a specific situation
a response to a identifiable, specific stimulus
TINBERGENS RESEARCH -
male sticklebacks are highly territorial in their spring mating season, when they also develop a red spot on their underbelly, if another male enters their territory, an aggressive FAP is initiated
the stimulus that triggers the innate releasing mechanism is the sight of the red underbelly, Tinbergen presented male sticklebacks with a series of wooden models of different colours and shapes
regardless of shape, if the model had a red spot, the male stickle back would aggressively display and attack it, but if there was no red spot, there was no aggression, even if the model was realistic
Tinbergen also found that the aggressive FAPs were unchanging from one encounter to another, and once triggered the aggression ran to completion without any further stimuli
EVALUATION -
RESEARCH SUPPORT -
there is evidence from research related to genetics and evolution, for example Brunner et als study showed that there is a significant genetic component to aggression in humans, and other studies also show that it is adaptive and therefore genetically based
these lines of research point towards an innate basis to aggressive behaviour which suggests that the ethological approach is correct in claiming that aggression is genetically determined, heritable and adaptive
RITUALISTIC AGGRESSION -
however aggression against members of the same species isnt just ritualistic
Goodall observed a four year war during which male chimps from one community killed all the members of another group in a systematic way, in some occasions a victim would be held down by several chimps and attacked for many minutes until it died
the violence would continue even if appeasement displays occurred, they didnt inhibit further aggression as the ethological explanation predicted and challenges its idea that intra species aggression has evolved into a self limiting and relatively harmless ritual
FAPs ARE NOT FIXED -
also lorenz’s view of fixed action patterns can now been seen to be outdated, he saw them an innate and unchanging, but Hunt has pointed out that FAPs are actually greatly influenced by environmental factors and learning experiences
for instance an aggressive FAP is typically made up of several behaviours in a series, and the duration of this varies between individuals and even in the same individual in encounter to encounter, this is because they are modifiable from experience, this means that many psychologists now use the term model behaviour pattern to reflect this, and that patterns of behaviour are far more flexible than lorenz thought
EVOLUTIONARY EXPLANATIONS OF HUMAN AGGRESSION -
SOCIAL PSYCHOLGICAL EXPLANATIONS OF AGGRESSION -
FRUSTRATION-AGGRESSION HYPOTHESIS -
THE ORIGINAL HYPOTHESIS -
Dollard and his colleugues first formulated the frustration aggression hypothesis, this states frustration always leads to aggression and aggression is always the result of frustration, and that aggression is a psychological drive similar to biological drives like hunger
we experience frustration when our attempts to reach a goal are blocked by an external factor, this creates a frustration drive which leads to aggressive thoughts/behaviour such as a violent fantasy or an outburst of violence
this removes the negative emotion and is called a catharsis, the aggression caused by the frustration is satisfied which reduces the drive, making further aggression less likely
it also suggest that aggression is not always expressed directly against the source of frustration, which leads to it being deflected onto another object or alternative
the source may be abstract such as the music industry or economic situation
the cause may be to powerful and we risk punishment by aggressing against it such as a headteacher or the police
the source may just be unavailable at the time for example it may have left the room
THE WEAPON EFFECT -
even if we become agnry we may still not behave aggressively, according to Berkowitz frustration only creates a readiness to be aggressive, but the presence of cues or stimuli in the environment make acting on the frustration more likely, this makes cues an additional element of the frustration aggression hypothesis
Berkowitz demonstrated the so called weapon effect in a lab study where participants were given real shocks by a confederate causing anger and frustration
the participants were later able to give fake shocks to the confederate, the number of shocks was greater when their was two guns placed on the table than in other conditions where there were no guns, this weapon effect supports Berkowitz’s contention that the presence of aggressive environmental cues stimulates aggression
RESEARCH ON THE FRUSTRATION AGGRESSION HYPOTHESIS -
Green carried out a study to investigate how aggression is affected by frustration
male university students completed a jigsaw puzzle, there frustration level was manipulated in one of three ways
for some participants, the puzzle was impossible to solve, for others they ran out of time because a confederate kept interfering, and lastly the confederate insulted some as they failed to solve the puzzle, all the participants all had the opportunity to give shocks to the confederate
the insulted participants gave the strongest shocks, followed by the interrupted group and then the impossible puzzle task participants, but all three groups selected more intense shocks than a non frustrated control group
EVALUATION -
RESEARCH SUPPORT -
there is research support for key features of the frustration aggression hypothesis, Marcus-Newhall conducted a meta analysis of 49 studies of displaced aggression, these studies investigated situations in which aggression had to be directed against a human target other than the one who caused the aggression
they concluded that displaced aggression is a reliable phenomenon, frustrated participants who were provoked but unable to retaliate directly against the source of their frustration were significantly more likely to aggress against an innocent party than people who weren’t provoked which shows aggression can be moved onto a weaker, more available target
ROLE OF CARTHARSIS -
but there is research to suggest that aggression may not be cathartic, Bushman found that participants who vented their anger by repeatedly hitting a punch bag actually became more aggressive rather than less
he suggested doing nothing was more effective at reducing aggression than venting and he argued that using venting to reduce anger is like trying to put out fire with petrol, adn that it does not work for people who think it has value which shows that a central assumption of the FA hypothesis may not actually be valid
FRUSTRATION AGGRESSION LINK -
the link between frustration and aggression is also complex, as early into the research into the FA hypothesis it was realised that frustration doesn’t always lead to aggression, and that aggression can occur without frustration
there is nothing ‘automatic’ about the link between the two, someone who feels frustrated may act in a range of ways, rather than being aggressive they may be helpless or determined, likewise someone who’s aggressive may be so for many reasons, this means that the FA hypothesis is inadequate as it only explains aggression is some cases and how it arises
SOCIAL LEARNING THEORY -
DE-INDIVIDUATION -
CROWD BEHAVIOUR -
de-individuation is a concept originally used by Le Bon to explain the behaviour of individuals in crowds, usually because we are easily identified by others, our behaviour is constrained by social norms
we live in a society where aggression is discouraged, but when we become part of a crowd, we lose restraint and have the freedom to behave in ways we wouldnt otherwise, we lose our sense of individual self identity and responsibility for our behaviour, we disregard norms and laws
responsibility becomes shared throughout the crowd, so we experience less personal guilt about directing harmful aggression at others
DE-INDIVIDUATION AND AGGRESSION -
Zimbardo distinguished between individuated and deindividuated behaviour, in an individual state, our behaviour is rational and normative, but in a deindividuate state we lose self awareness, stop monitoring and regulating our own behaviour, ignore social norms and ‘live for the moment’ failing to form long term plans
the conditions of deindividuation which promotes aggressive behaviour includes darkness, drugs, alcohol, uniforms, masks and disguises, but a major factor is anonymity
according to Dixon and Mahendran anonymity shapes crowed behaviour, we have less of a fear of retribution because we are small and unidentifiable part of a faceless crowd, the bigger the crowd, the more anonymous we are, anonymity provides fewer opportunities for others to judge us negatively
REDUCED SELD AWARNESS -
the experience of de-individuation as part of a faceless crowd creates a greater likelihood of aggression, but according to Dunn and Rogers, this isnt due to anonymity directly but to a consequence of anonymity, this is explained in terms of two types of self-awareness -
PRIVATE SELF AWARENESS - concerns how we pay attention to our own feelings and behaviour, this is reduced when we are part of a crowd, our attention becomes focused on the events around us so we pay less attention to our own beliefs and feelings, we are less self critical and thoughtful which promotes a deindividuated state
PUBLIC SELF AWARNESS - refers to how much we care about what other people think about our behaviour, this is also reduced in crowds and we realise that we are just one individual amongst many, we are anonymous and our behaviour is less likely to be judged by others so we no longer care about that they think about us making us less accountable for our actions
RESEARCH ON DEINDIVIDUATION -
Dodd asked 229 undergraduate students if they could do anything without it being detected or causing them to be held accountable, what would they do, they knew the responses were anonymous, and three independent rater’s who didnt know the hypothesis decided which categories of antisocial behaviour the responses belonged to
he found that 36% of the responses involved some form of antisocial behaviour, 26% were criminal acts, the most common was rob a bank, but some opted for murder, rape or assassination of political figures, only 9% were prosocial, meaning they would help people
in terms of how people imagine they would behave, this study demonstrates a link between anonymity, deindividuation and aggressive behaviour
EVALUATION -
RESEARCH SUPPORT -
research support comes from Douglas and McGarty’s study, they looked at aggressive online behaviour in chatrooms and the use of instant messaging, they found a strong correlation between anonymity and flaming
they found the most aggressive messages cam from those who had decided to hide their real identity, a common behaviour of online trolls, which has been implicated in high profile cases of self harm and suicide, this supports a link between aggressive behaviour and anonymity, a key element of deindividuation
REAL WORLD DEINDIVIDUATION -
another strength is deindividuation can explain the aggressive behaviour of baiting crowds, Mann et al investigated instances of suicidal jumpers, he identified 21 cases reported in US newspapers of a crowd gathering to bait a jumper
these incidents tended to occur in darkness, the crowds were usually large, and the jumpers relatively distant from the crowd, which are factors predicted by the deindividuation theory to lead to a state of deindividuation in crowds, which leads to aggressive baiting, this means there must be some validity to the ideas that a large group can become aggressive in a de-individuated, faceless crowd
ROLE OF NORMS -
however deindividuated behaviour is normative rather than antinormative, deindividuation theory argues that we behave in ways that are contrary to social norms, when we are less privately self aware
however in their SIDE model, Spears and Lea argue that deindividuation actually leads to behaviour that conforms to group norms, these may be antisocial norms, but can also be prosocial norms
this happens because anonymity shifts an individuals attention from their private identity to their social identity as a group member which suggest people in a deindividuated state still remain sensitive to the effects of social norms rather than ignoring them
INSTITUTIONAL AGGRESSION IN THE CONTEXT OF PRISONS -
MEDIA INFLUENCES ON AGGRESSION -
DESENSITISATION, DISINHIBITION AND COGNTIVE PRIMING -