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Aggression

AQA A2 Psychology- PSYA3- Aggression.
by

Rachel Scowcroft

on 7 December 2012

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Transcript of Aggression

Aggression Social learning theory Deindividuation Institutional aggression Neural mechanisms Genetic factors Evolutionary explanations Explanations of group display Social learning theory Social learning theory Mental representation Observation Production of behaviour Bandura and Waters believed that aggression could not be explained using traditional learning theory where only direct experience was seen as responsible for the acquisition of new behaviours.
Social learning theory suggests that we also learn by observing others.

We learn the specifics of aggressive behaviour (e.g. the forms it takes, how often it is enacted, the situations that produce it and the targets towards which it is directed).

This is not to suggest that the role of biological factors is ignored in this theory, but rather that a person's biological makeup creates a potential for aggression and it is the actual expression of aggression that is learned. Children primarily learn their aggressive responses through observation- watching the behaviour of role models and then imitating that behaviour. Whereas Skinner's operant conditioning theory claimed that learning takes place through direct reinforcement, Bandura suggested that children learn just by observing role models with whom they identify.

Children also observe and learn about the consequences of aggressive behaviour by watching others be reinforced or punished. This is called indirect or vicarious reinforcement.

Children witness many examples of aggressive behaviour at home and at school, as well as on TV and in films. By observing the consequences of aggressive behaviour for those who use it, a child gradually learns something about what is considered appropriate (and effective) conduct in the world around them. Thus they learn the behaviours (through observation) and they also learn whether and when such behaviours are worth repeating (through vicarious reinforcement). Bandura claimed that in order for social learning to take place, the child must form mental representations of events in their social environment.

The child must also represent possible rewards and punishments for their aggressive behaviour in terms of expectancies of future outcomes.

When appropriate opportunities arise in the future, the child will display the learned behaviour as long as the expectation of reward is greater than the expectation of punishment. If a child is rewarded (i.e. gets what he wants or is praised by others) for a behaviour, he or she is likely to repeat the same situation in similar situations in the future. A child who has a history of successfully bullying other chlidren will therefore come to attach considerable value to aggression.

In addition to foming expectancies of the likely outcomes of their aggression, children also develop confidence in their ability to carry out the necessary aggressive actions. Children who were not successful in this form of behaviour in the past have less confidence (lower sense of self-efficacy) in their ability to use aggression successfully to resolve conflicts, and therefore may turn to other means. Bobo Doll Studies Bandura et al Bobo doll studies Vicarious learning Validity/Ethical issues Role of vicarious learning Participants in this study were male and female children ranging from 3-5 years. Half were exposed to adult models interacting aggressively with a life-sized inflatable Bobo doll and half exposed to models that were non-aggressive towards the doll.
The model displayed distinctive physically aggressive acts towards the doll, e.g. striking it on the head with the mallet and kicking it about the room, accompanied by verbal aggression, such as saying "POW".
Following exposure to the model, children were frustrated by being shown attractive toys which they were not allowed to play with. They were then taken to a room where, among other toys, there was a Bobo doll.
Children in the aggression condition reproduced a good deal of phyiscally and verbally aggressive behaviour resembling that of the model. Children in the non-aggressive group exhibited virtually no aggression towards the doll.
Approximately 1/3 of the children in the aggressive condition repeated the model's verbal responses while none of the children in the non-aggressive group made such remarks. Boys reproduced more imitative physical aggression than girls, but they did not differ in their imitation of verbal aggression. It is possible that the children in Bandura's studies were aware of what was expected of them (demand characteristics). Noble reports that one child arriving at the laboratory for the experiment said, "Look Mummy, there's the doll we have to hit." These studies also focus on aggression towards a doll rather than a real person, who would tend to hit back. However, responding to this criticism, Bandura procuded a film of a young woman beating up a live clown. When the children went into the other room, the live clown was there and the children proceeded to punch him, kick him and hit him with hammers.

Ethical issues make it difficult to test social learning theory experimentally. Exposing children to aggressive behaviour with the knowledge that they may reproduce it in their own behaviour raises ethical issues concerning the need to protect participants from psychological and physical harm. As a result, experimental studies such as the Bobo doll studies would no longer be allowed to take place. This means that it is difficult to test experimental hypotheses about the social learning of aggressive behaviour in children, and consequently difficult to establish the scientific credibility of the theory by this means. Although this study tells us that children do acquire aggressive responses as a result of watching others, it does not tell us much about why a child would be motivated to perform the same behaviours in the absence of the model.

In a later study, Bandura and Walters found that children who saw the model being rewarded for aggressive acts showed a low level of aggression in their play, while those in the no-reward, no-punishment control group were somewhere in between these two levels of aggression.

Bandura called this type of learning vicarious learning- the children were learning about the likely consequences of actions, and then adjusting their subsequent behaviour accordingly. A major strength of social learning theory is that, unlike operant conditioning, it can explain aggressive behaviour in the absence of direct reinforcement.

Although Bandura et al's participants behaved more aggressively after observing an aggressive model, at no point were the children directly rewarded for any action, either aggressive or non-aggressive.

Consequently, the concept of vicarious learning is necessary to explain these findings. Role of punishment Applicability to adults In the Bandura and Walters study, did the children in the non-aggression group show low levels of aggression because the punishment prevented learning or did the punishment prevent performance of the behaviour?

To test this, Bandura repeated the study but now, after exposure to the model, offered rewards to all the children for performing the model's aggressive behaviours. In this case all 3 groups performed a similar number of imitative acts.

This shows that learning does take place regardless of reinforcements but that production of behaviours is related to selective reinforcements. The studies in this area have involved children, but does social learning theory explain adult behaviour as well?

Phillips found that daily homicide rates in the US almost always increased in the week following a major boxing match, suggesting that viewers were imitating behaviour they watched and that social learning is evident in adults as well as children. Deindividuation Zimbardo Deindividuation Process of deindividuation Nature of deindividuation Zimbardo introduced the theory of deindividuation. The theory suggests that people, when part of a relatively anonymous group, lose their personal identity and therefore lose their inhibitions about violence.

Deindividuation theory has been used as an explanation of the collective behaviour of violent crowds, mindless hoolingans and social atrocities, such as genocide. Colman found that in some countries, deindividuation has even been accepted as ground for extenuating circumstances in murder trials.

Deindividuation theory is based, to a large extent, on the classic crowd theory of Le Bon. He described how an individual was transformed when part of a crowd. He claimed that, in a crowd, the combination of anonymity, suggestibility and contagion mean that a "collective mind" takes possession of the individual. As a consequence, the individual loses self-control and becomes capable of acting in a way that goes against personal or social norms. Deindividuation is a psychological state characterised by lowered self-evaluation and decreased concerns about evaluation by others. This leads to an increase in behaviour that would normally be inhibited by personal or social norms.

The psychological state of deindividuation is aroused when individuals join crowds or large groups. Zimbardo identified anonymity (e.g. wearing a uniform) and altered consciousness due to drugs or alcohol as factors that contribute to deindividuation.

Although Zimbardo has stressed that these same conditions may also lead to an increase in prosocial behaviours (for example crowds at music festivals and large religious gatherings), the focus of deindividuation theory has been almost exclusively on antisocial behaviour. People normally refrain from acting in an aggressive manner partly because there are social norms inhibiting such "uncivilised" behaviour and partly because they are easily identifiable. Being anonymous (and therefore effectively accountable) in a crowd has the psychological consequence of reducing inner restraints and increasing behaviours that are easily inhibited.

According to Zimbardo, being part of a crowd can diminish awareness of our own individuality. In a large crowd, each person is faceless and anonymous- the larger the gruop, the greater the anonymity. There is diminished fear of negative evaluation of actions and a reduced sense of guilt. Conditions that increase anonymity also minimise concerns about evaluation by others, and so weaken the normal barriers to antisocial behaviour that are based on guilt or shame. Research support Electric shocks Anonymity Zimbardo- Groups of 4 female undergraduates were required to deliver electric shocks to another student to "aid learning". Half of the participants wore bulky lab coats and hoods that hid their faces, sat in separate cubicles, and were never referred to by name. This was the deindividuated condition. The other participants wore their normal clothes, were given large name tags to wear and were introduced to each other by name. They were also able to see each other when seated at the shock machines. Both sets of participants were told they could see the person being shocked. Participants in the deindividuated condition shocked the "learner" for twice as long as the identifiable participants.

Zimbardo concluded that anonymity is an important determinant of deindividuation. However, Prentice-Dunn et al claim that it is reduced self-awareness, rather than simply anonymity, that leads to deindividuation. If an individual is self-focused, they tend to focus on, and act according to, their internalised attitudes and moral standards, thus reducing the likelihood of anti social behaviour. If the individual submerges themselves within a group, they may lose this focus, becoming less privately self-aware, and therefore less able to regulate their own behaviour. Zimbardo's study led to the suggestion that anonymity, a key component of the deindividuation process, increased aggressiveness.

Rehm et al investigated whether wearing a uniform when part of a sports team also increased aggressive behaviour. They randomly assigned German schoolchildren to handball teams of 5 people, half the teams wearing the same orange shirts, and the other half wearing their normal street clothes. The children wearing orange (who were harder to tell apart) played the game consistently more aggressively than the children in their everyday clothes.

Mullen analysed newspaper cuttings of 60 lynchings in the United States between 1899 and 1946. He found that the more people there were in the mob, the greater the savagery with which they killed their victims. Mann used the concept of deindividuation to explain a bizarre aspect of collective behaviour- the "baiting crowd". The baiting crowd lends support to the notion of the crowd as a deindividuated "mob".

Mann analysed 21 suicide leaps reported in US newspapers in the 1960s and 1970s. He found that in 10 of the 21 cases where a crowd had gathered to watch, baiting had occurred (i.e. the crowd had urged the potential suicide to jump).

These incidents tended to occur at night, when the crowd was large and some distance from the person being taunted (particularly when the "jumper" was high above them). All these features were likely to produce a state of deindividuation in the members of the crowd. Suicide jumpers Neurotransmitters Dopamine Antidepressants Serotonin Non-human studies Dopamine and serotonin are neurotransmitters (chemicals that enable impulses within the brain to be transmitted from one area of the brain to another). Low levels of serotonin and high levels of dopamine have been associated with aggression in animals and humans.

Lavine- Increases in dopamine activity via the use of amphetamines have also been associated with increases in aggressive behaviour.
Buiteaar- Antipsychotics, which reduce dopamine activity in the brain, have been shown to reduce aggressive behaviour in violent delinquents.

Although research is fairly inconclusive about the causal role of dopamine in aggression, recent research suggests that its influence might be as a consequence rather than a cause. Couppis & Kennedy found that in mice, a reward pathway in the brain becomes engaged in response to an aggressive event and that dopamine is involved as a positive reinforcer in this pathway. This suggests that individuals will intentionally seek out an aggressive encounter solely because they experience a rewarding sensation from it. Serotonin is thought to reduce aggression by inhibiting responses to emotional stimuli that might otherwise lead to an aggressive response.

Low levels of serotonin in the brain have been associated with an increased susceptibility to impulsive behaviour, aggression, and even violent suicide.

Some drugs are thought to alter serotonin levels and thus increase aggressive behaviour. Mann et al gave 35 healthy subjects dexfenfluramine, which is known to deplete serotonin. Using a questionnaire to assess hostiity and aggression levels, they found that dexfenfluramine treatment in males (but not femaes) was associated with an increase in hostility and aggression scores. If low levels of serotonin are associated with low impulse control and aggressive behaviour, drugs that clinically raise serotonin levels should produce a concurrent lowering in aggression.

Bond has established that this is exactly what happens in clinical studies of antidepressant drugs that elevate serotonin levels. She established that such drugs tend to reduce irritability and impulsive aggression. Raleigh et al have added support for the importance of serotonin in aggressive behaviour in a study of vervet monkeys. They found that individuals fed on experimental diets high in tryptophan (which increases serotonin levels in the brain) exhibited decreased levels of aggression. Individuals fed on diets that were low in tryptophan exhibited increased aggressive behaviour, suggesting that the difference in aggression could be attributed to their serotonin levels.

Popova et al- In animals that are selectively bred for domestication and for increasingly docile temperaments, there is a corresponding increase, over generations, in brain concentrations of serotonin. Hormonal mechanisms Testosterone Evaluation The challenge hypothesis Cortisol The male sex hormone testosterone is thought to influence aggression from young aduthood onwards due to its action on brain areas involved in controlling aggression.

Dabbs et al measured salivary testosterone in violent and non-violent criminals. Those with the highest tesosterone levels had a history of primarily violent crimes whereas those with the lowest levels had committed only non-violent crimes.

Studies of non-prison populations have found similar trends. Lindman et al found that young males who behaved aggressively when drunk had higher testosterone levels than those who did not act aggressively. Wingfield et al proposes that, in monogamous species, tesosterone levels should ony rise above the baseline breeding level in response to social challenges, such as male-male aggression or threats to status.

As the human species is considered to be monogamous, this woud predict that male testosterone levels would rise sharply in response to such challenges.

In such situations, a testosterone surge is to be expected, with a consequent increase in aggression, provided the threat is deemed relevant to reproductive competition, e.g. a dispute over a female. Albert et al claim that despite many studies showing a positive correlation between testosterone and aggression, other studies find no such relationship, particularly those that have compared testosterone levels of aggressive and less aggressive individuals. In addition, most studies showing a positive correlation have involved small samples of men within prisons, using either self-report measures of aggression or judgements based solely on the severity of the crime committed.

Mazur suggests we should distinguish aggression from dominance. Individuals act aggressively when their intent is to inflict injury, whereas they act dominantly if their wish is to achieve or maintain status over another. Mazur claims that aggression is just one form of dominance behaviour. In non-human animals the influence of testosterone on dominance behaviour might be shown in aggressive behaviour. In humans, the influence of testosterone on dominance is likely to be expressed in more varied and subtle ways (e.g. through status striving behaviour). Dabbs et al- Cortisol appears to have a mediating effect on other aggression-related hormones such as testosterone, possibly because it increases anxiety and the likelihood of social withdrawal. High levels of cortisol inhibit testosterone levels and so inhibit aggression.

Virkkunen- Studies have reported low levels of cortisol in habitual violent offenders.
Tennes & Kreye- Low levels of cortisol were also found in violent schoolchildren.
This suggests that although relatively high testosterone is the primary biochemical influence on aggression, low cortisol also plays an important role by increasing the likelihood of aggressive behaviour.

The moderating effect of cortisol is supported in McBurnett et al's 4 year study of boys with behavioural problems. The boys with consistently low cortisol levels began antisocial acts at a younger age & exhibited 3 times the number of aggressive symptoms compared to boys with higher or fluctuating cortisol levels. Neurotransmitters Scerbo and Raine's meta analysis of 29 studies examined neurotransmitter evels in antisocial children and adults.

These studies consistently found lower levels of serotonin in individuals described as being aggressive, but found no significant rise or fall in dopamine levels.

Indications of reduced levels of serotonin were found in all antisocial groups, but were particularly marked in those individuals who had attempted suicide.

This suggests that serotonin depletion leads to impulsive behaviour, which in turn may lead to aggressive behaviour in various forms. A gene for aggression? The role of MAOA Genetics & violent crime Gene-envrionment interaction Inheritance of criminal violence Although no individual gene for aggression has been identified in humans, a gene responsible for producing a protein called monoamine oxidase A (MAOA) has been associated with aggressive behaviour. MAOA regulates the metabolism of serotonin in the brain, and low levels of serotonin are associated with impulsive and aggressive behaviour.

Brunnet et al- A study of a Dutch family found that many of its male members behaved in a particularly violent and aggressive manner, and a large proportion had been involved in serious crimes of violence, including rape and arson. These men were found to have abnormally low levels of MAOA in their bodies, and a defect in this gene was later identified. Caspi et al- In a study of 500 male children, researchers discovered a variant of the gene associated with high levels of MAOA and a variant associated with low levels.

Those with low levels of MAOA were significantly more likely to grow up to exhibit antisocial behaviour but only if they had been maltreated as children.

Children with high levels of MAOA who were maltreated, and those with low levels who were not maltreated, did not display antisocial behaviour.

This shows that it is the interaction between genes and environment that determines behaviours, such as aggression. Researchers do not suggest that there is a gene for violent crime. Rather it is claimed that inherited temperamental or personality characteristics place some individuals more at risk of committing violent crime.

Adoption studies have shown that the highest rates of criminal violence in adopted children occur when both biological and adoptive parents have a history of violent crime- clear evidence of a gene-environment interaction.

However, in Brennan and Mednick's series of adoption studies, the criminal history of an adopted male was compared with the criminal history of both his biological and his adoptive fathers. The studies found that genetic influences were significant in cases of property cime but not in cases of violent crime. Studies that have investigated the role of genetic factors often fail to distinguish between violent and non-violent crime, making it more difficult to untangle the role of genetic factors in specifically aggressive violence. These studies also often fail to distinguish between criminals who are habitually violent and those for whom their violent crime is a one-off.

The evidence for violent crime being inherited is also far from conclusive. Walters's meta-analysis of studies in this area found only a low to moderate correlation between heredity and crime, with better designed and more recently published studies providing less support for the gene-crime hypothesis than more poorly designed and earlier published studies.
A more recent review of published studies of youth crime concluded "The data do not suggest a strong role for heredity in violence." Aggression: nature or nurture? Twin studies Research support Adoption studies Problems of assessing aggression Monozygotic (identical) twins share all of their genes, while dizygotic (non-identical) twins share only 50%. In twin sudies, researchers compare the degree of similarity for a particular trait (such as aggression) between sets of monozygotic (MZ) twins to the similarity between sets of dizygotic (DZ) twins.

If the MZ twins are more alike in terms of their aggressive behaviour, then this should be due to genes rather than environment (both types of twin share the same environment as each other but monozygotic twins are more genetically alike).

Most twin studies have focused on criminal behaviour generally, but one of the few studies to specifically study aggressive behaviour using adult twin pairs found that nearly 50% of the variance in direct aggressive behaviour could be attributed to genetic factors (Coccaro et al). Miles and Carey carried out a meta-analysis of 24 twin and adoption studies that supported the genetic basis of aggression. Most studies had relied on parental or participants' self-reports of aggressive tendencies, although some involved observation of aggressive behaviour. The results suggested a strong genetic influence that could account for as much as 50% of the variance in aggression. Age differences were notably important, with both genes and family environment being influential in determining aggression in youth, but at later ages the influence of rearing environment decreased and the influence of genes increased.

A later meta-analysis by Rhee and Waldman combined the results of 51 twin and adoption studies and also concluded that aggressive antisocial behaviour was largely a product of genetic contributions. However, in both meta-analyses, several variables, including age of participant and assessment method for aggression, moderated the genetic influence on aggression, suggesting that although genetic factors play a significant part in the development of aggressive behaviours, the influence of other factors affects their expression. Many of the reported studies of aggression have relied on either parental or self-reports of aggressive behaviour, whereas other studies have made use of observational techniques. The Miles and Carey meta-analysis found that genetic factors explained a large proportion of the variance in aggressive behaviour in studies that had used parental or self-reports.

However, those that had made use of observational ratings showed significantly less genetic contribution and a greater influence of environmental factors. In a replication of Bandura et al's Bobo doll study, twin pairs were encouraged to act aggressively towards the doll by being exposed to an adult model who also acted aggressively towards it. Researchers found no difference in correlations between monozygotic and dizygotic twin pairs, suggesting that individual differences in agression were more a product of environmental influences (e.g. family upbringing) than genetic influences (Plomin et al). Adoption studies can help to untangle the relative contributions of the environment and heredity in aggression.

If a positive correlation is found between aggressive behaviour in adopted children and aggressive behaviour in their biological parents, a genetic effect is implied.

If a positive correlation is found between the adoptee's aggressive behaviour and the rearing family, then an environmental effect is implied.

Hutchings & Mednick- A study of over 14,000 adoptions in Denmark found that a significant number of adopted boys with criminal convictions had biological parents (particularly fathers) with criminal convictions. This provides evidence for a genetic effect. The connection between genetic factors and aggression is far from straightforward because of problems determining what is, and what is not, a product of genetic inheritance.

It is difficult to establish genetic contributions to aggressive behaviour because:
More than 1 gene usually contributes to a given behaviour
As well as genetic factors there are many non-genetic (i.e. environmental) influences on the manifestation of aggressive behaviour.
These influences may interact with each other. Genetic factors may affect which environmental factors have an influence, and vice versa (gene-environment interaction). Determining role of genetics Jealousy Jealousy Mate retention and violence Cuckoldry & sexual jealousy Evolutionary psychologists argue that the different reproductive challenges faced by our ancestors led to a number of evolved sex differences, including sex differences in jealousy. Male sexual jealousy as a result of real or suspected infidelity is a frequently cited cause of violence in interpersonal relationships. In many cultures, the murder of an adulterous wife is or her lover is not only condoned but encouraged.

Daly and Wilson claim that men have evolved several different strategies to deter their female partners from committing adultery. These range from vigilance to violence, but all are fuled by male sexual jealousy, an adaptation that evolved specifically to deal with the threat of paternal uncertainty. Unlike women, men can never be entirely certain that they are the fathers of their children, as fertilisation is hidden from them, inside the woman.

As a result, men are always at risk of cuckoldry, the reproductive cost that might be infllicted on a man as a result of his partner's infidelity.

The consequence of cuckoldry is that the man might unwittingly invest his resources in offspring that are not his own.

The adaptive functions of sexual jealousy, therefore, would have been to deter a mate from sexual infidelity, thereby minimising the risk of cuckoldry. Buss suggests that males have a number of strategies that have evolved specifically for the purpose of keeping a mate. These include resricting their partners' autonomy ("direct guarding") and "negative inducements" in the form of violence or threats of violence to prevent her from straying.

Because sexual jealousy is a primary cause of violence against women, those who are perceived by their partner to be threatening infidelity (e.g. by looking at another man), are more at risk of violence than those who are not.

Dobash & Dobash- Studies of battered women have shown that in the majority of cases, women cite extreme jealousy on the part of their husbands or boyfriends as the key cause of the violence directed towards them. Research support Shackelford et al used a survey method to test evolutionary psychology predictions concerning mate retention strategies. They ised 461 men and 560 women in the US. All participants were in committed, heterosexual relationships.

Male participants answered questions about their use of mate retention techniques, and were assessed on how often they performed each of 26 different types of violent act against their partners. Female participants answered questions concerning their partners' use of male retention techniques and the degree to which their partners used violence against them.

Mens' use of 2 broad types of retention technique (intersexual negative inducements and direct guarding) was positively correlated with their violence scores. In addition, use of emotional manipulation (e.g. saying they would kill themselves if their partner left) as a specific tactic appeared to consistently predict men's violence against women. Results from female participants confirmed this trend, with reports of direct guarding and intersexual negative inducements being positively correlated with their experience of female-directed violence.

In addition, women reported that those partners who frequently used specific mate retention tactics of vigilance and emotional manipulation were most likely to use violence against them. As with males, age and relationship duration made no difference to the reported trends. In the Shackelford et al study, data was collected using a survey technique.

Surveys are a form of self-report technique that have particular problems, especially when used in sensitive areas, such as violence against a spouse.

Answers may not be truthful because of the social desirability bias- a tendency to respond in a way that will be viewed favourable by others. This takes the form of over-reporting desirable behaviour and under-reporting undesirable relationship. Sports Advantage of xenophobia Territoriality Xenophobia in sport Testosterone & territoriality Wilson claims that xenophobia (a fear and hatred of strangers or foreigners) has been documented in "virtually every group of animals displaying higher forms of social organisation".

Natural selection has favoured those genes that caused human beings to be altruistic towards members of their own group but intolerant towards outsiders.

Shaw & Wong argue that the mechanisms that prompt suspicion towards strangers would have been favoured by natural selection. This would have enabled our ancestors to avoid attack, and so leave behind more offspring.

MacDonald suggests that from an evolutionary perspective, it is adaptive to exaggerate negative stereotypes about outsiders, as the overperception of threat is less costly than its underperception.

Social psychological theories such as deindividuation do not tell the whole story about the origins of aggression in groups.

Aggressive group displays are a product of some external stimulus that triggers the behaviour in question (known as the proximate cause).

However, this may conceal the adaptive or "real" reason why the behaviour evolved in the first place, known as its ultimate cause.

Aggressive group displays emerged among our distant ancestors due to the fact that they increased their fitness in some way.
Nowadays, similar situations trigger the same response, even though the original function of the behaviour may no longer be relevant. Adaptive Social learning theory can be used to explain cultural differences in aggression. Among the !Kung San of the Kalahari Desert, aggression is comparatively rare. Why is this the case?
The answer lies in the child-rearing practises of the !Kung San.

1- When 2 children argue or fight, parents neither reward nor punish them, but physically separate them and try to distract their attention onto other things.

2- Parents do not use physical punishment, and aggressive postures are avoided by adults and devalued by the society as a whole. The absence of direct reinforcement of aggressive models means there is little opportunity for !Kung San children to acquire aggressive behaviours. A strength of social learning theory is that it can explain differences in aggressive and non-aggressive behaviour both between and within individuals. Wolfgang and Ferracuti's "culture of violence" theory proposes that, in large societies, some subcultures develop norms that sanction violence to a greater degree than the dominant culture.
Some cultures may emphasise and model non-aggressive behaviour, producing individuals that show low levels of aggression. Differences within individuals can be related to selective reinforcement and context-dependent learning. People respond differently in different situations because they observed that aggression is rewarded in some situations and not others, i.e. they learn behaviours that are appropriate to particular contexts. Cultural differences Individual differences Evaluation Importance of local group norms Prosocial consequences Lack of support Johnson & Downing explored the idea that rather than deindividuation automatically increasing the incidence of aggression, any behaviour produced could be a product of local group norms.

They used the same experimental conditions as in Zimbardo's electric shock study, but this time participants were made anonymous by means of a mask and overalls (reminiscent of the Ku Klux Klan), or by means of nurses' uniforms.

Participants shocked more than a control condition when dressed in the KKK uniforms, but actually shocked less than the controls when dressed as nurses.

This finding illustrates that people respond to normative cues associated with the social context in which they find themselves. In this study, participants dressed as Ku Klux Klansmen clearly felt that aggressive behaviour was more appropriate than did the participants dressed as nurses. Evidence for deindividuation theory is mixed.

Postmes and Spears's meta-analysis of 60 studies for deindividuation concludes that there is insufficient support for the major claims of deindividuation theory.

Postmes and Spears found that disinhibition and antisocial behaviour are not more common in large groups and anonymous settings.

Nor was there much evidence that deindividuation is associated with reduced self-awareness, or that reduced self-awareness increases aggressive behaviour. Deindividuation can increase prosocial behaviour. Although most of the research on deindividuation has attempted to find a relationship between deindividuation and antisocial behaviour, some studies have shown that deindividuation may also increase the incidence of prosocial behaviour. Spivey and Prentice-Dunn found that deindividuation could lead to either prosocial or antisocial behaviour depending on situational factors. When prosocial environmental cues were present (such as a prosocial model), deindividuated participants performed significantly more altristic acts (giving money), and significantly fewer antisocial acts (giving electric shocks) compared to a control group.

The desirable effects of deindividuation can also be found in cyberspace. Francis et al found that adolescents reported feeling significantly more comfortable seeking help with mental health problems under the deindividuated circumstances of Internet chatrooms compared to the individuated circumstances of a personal appointment with a health professional. Gender bias Cannavale et al found that male and female groups responded differently under deindividuation conditions reflecting a gender bias in the theory.
An increase in aggression was obtained only in the all-male groups.

This was also the finding of Diener et al, who found greater disinhibition of aggression (i.e. removal of the normal inhibitions concerning aggression) in males. Thus, evidence indicates that males may be more prone to disinhibition of aggressive behaviour when deindividuated, than females. Cultural differences Watson collected data on the extent to which warriors in 23 societies changed their appearance prior to going to war and the extent to which they killed, tortured or mutilated their victims.

The societies where warriors changed their appearance (e.g. through war paint, tribal costumes etc) were more destructive toward their victims compared to those who did not change their appearance.

As Zimbardo comments, when we want "usually peaceful young men to harm and kill other men... it is easier to do so if they first change their appearance to alter their usual external facade." Institutional aggression within groups (prisons) Importation model Deprivation model Evaluation Evaluation Irwin and Cressey claim that prisoners bring their own social histories and traits with them into prison, and this influences their adaptation to the prison environment. Irwin and Cressey argue that prisoners are not "blank slates" when they enter prison, and that many of the normative systems developed on the outside would be "imported" into the prison.

Within prison environments, gang membership is consistently related to violence and other forms of antisocial behaviour. Allender and Marcell found that gang members disproportionately engage in acts of prison violence. Pre-prison gang membership appears to be an important determinant of prison misconduct. Members of street gangs offend at higher levels than their non-gang counterparts and account for a disproportionate amount of serious and violent crime.

For example, Huff found that gang members in the US were 10 times more likely to commit a murder and 3 times more likely to assault someone in public than were non-gang members of a similar age and background. The importation model has received some research support, particularly in terms of individual factors (age, educational level, race etc). Harer and Steffensmeier collected data from 58 US prisons and found that black inmates had significantly higher rates of violent behaviour but lower rates of alcohol-related and drug-related misconduct than white inmates. These patterns parallel racial differences in these behaviours in US society and so support the importation model.

Evidence from DeLisi et al challenges the claim that pre-prison gang membership predicts violence whilst in prison. They found that inmates with prior street gang involvement were no more likely than other inmates to engage in prison violence.
This lack of a correlation between the two might be explained by the fact that violent gang members tend to be isolated from the general inmate population, therefore greatly restricting their opportunities for violence. Fischer found that isolating known gang members in a special management unit reduced the rates of serious assult by 50%. This model argues that prisoner or patient aggression is the product of the stressful and oppressive conditions of the institution itself. These include crowding, assumed to increase fear and frustration levels, and staff experience. Hodgkinson et al found that trainee nurses are more likely to suffer violent assault than experienced nurses, and in the prison setting, length of service was also a significant factor, with Davies and Burgess finding that more experienced officers were less likely to suffer an assault.

Sykes described the specific deprivations that inmates experience within prison and which might be linked to an increase in violence. These included the loss of liberty, the loss of autonomy and the loss of security. For example, Sykes found that the potential threat to personal security increased anxiety levels in inmates, even if the majority of prisoners posed no significant threat to them. Inmates may cope with the pains of imprisonment by withdrawing through seclusion in their cell or living space, whereas others choose to rebel in the form of violence against other prisoners or against staff. There is substantial research evidence to support the claim that peer violence is used to relieve the deprivation imposed by institutional cultures, such as prisons.

McCorkle et al found that overcrowding, lack of privacy and the lack of meaningful activity all significantly influence peer violence. However, research in this area is not consistent in its findings. Research in psychiatric institutions, eg. Nijman et al, found that increased personal space failed to decrease the level of violent incidents among patients.

Jiang and Fisher-Giorlando found support for both the deprivation and importation models as explanations of prison violence. They found that the deprivation model was better able to explain violence against other inmates.
The deprivation model is challenged by Poole and Regoli's research. They found that the best indicator of violence among juvenile offenders was pre-institutional violence regardless of any situational factors in the institution. Institutional aggression between groups (genocide) Genocide Dehumanisation Importance of bystanders Obedience to authority In some cases, the "institution" may refer to a whole section of society, defined by ethnicity, religion or some other significant feature. Violence may occur when one institution's relationship with another is characterised by hatred and hostility. The murder of 6 million Jews by Nazis during World War 2 is an example of this form of institutional aggression.

Staub outlined 5 stages in the process of genocide that explain how diffcult social conditions such as those found in pre-war Germany can replidy escalate into victimisation of a target group. Staub's model emphasises the importance of bystander intervention in preventing genocide.

It appears that doing nothing merely allows the killing to continue unbated, and may even escalate it by signalling apathy or consent.

However, bystander intervention does not necessarily end institutional aggression, as there is an important difference between the effect of intervention on duration and on severity of violence. In international or civil conflict, it might also hasten perpetrators to step up their genocidal policy within a reduced period of time- so while a conflict may end sooner, more people may be killed. For example, in the Rwandan genocide, 800,000 people died in 100 days. Although human beings usually have moral inhibitions about killing fellow humans, this changes if the target group is dehumanisted so that its members are seen as worthless animals and therefore not worthy of moral consideration.
In the Rwandan genocide, the influential Hutu controlled "hate" radio station RTLM encouraged Hutu listeners to murder their Tutsi as "cockroaches".

Dehumanisation may also explain violence against immigrants, seen by some as "polluting threats to the social order" (O'Brien). Recent research suggests that personality may play an important role in this respect. Milgram believed that the Holocaust was primarily the result of situational pressures that forced Nazi sodiers to obey their leaders regardless of any personal moral objections.

He argued that if so many participants in his study could administer painful electric shocks to a victim simply because they were told to do so by someone in authority, the mighty Nazi regime would have no trouble making soldiers kill innocent, unharmed people.

Mandel rejects Milgram's claims that obedience to authority was sufficient to explain the behaviour of Holocaust perpetrators. He argues that Milgram's account is monocausal (i.e. ignores other possibe causes) and simply does not match the historical record. For example, Goldhagen suggests that the main causal factor in the atrocitires was a form of anti-Semitism so deepy entrenched in the German people at the time that they implicitly condoned the elimination of millions of innocent Jews. Research support A real-world application of the deprivation model happened at HMP Woodhill in the early 1990s.

David Wilson reasoned that if most violence occurs in environments that are hot, noisy and overcrowded, then this could be avoided by reducing these 3 factors.

Wilson set up two units for violent prisoners that were less claustrophobic and "prison-like" and gave a view to outside.
The typical noise associated with prison life was reduced and masked by music from a local radio station.
Temperature was lowered to that it was no longer stiflingly hot.

These changes virtually eradicated assaults on prison staff and other inmates, which supports the deprivation model.

However, political pressure led to the units changing their regimes and developing in a different direction. People were unhappy with the worst prisoners being given the best things. Dehumanisation Social dominance orientation (SDO) is a personality variable which predicts social and political attitudes.

People who are high in SDO endorse social hierachies and inter-group inequality, and see the world as a "competitive jungle".

Esses et al has demonstrated that individuals high in SDO have a tendency to dehumanise outgroup members, and in particular foreign refugees and asylum seekers.

Media depictions of refugees portrayed as violating immigration procedures and trying to cheat the system cause greater contempt in high SDO individuals than in low SDO individuals and lack of sympathy for refugees in general.

These negative attitudes become rationalised through "legitimising myths" (e.g. that foreign refugees are by nature socially deviant) which indicate to the high SDO individual that these groups deserve our hostility because they are somehow less human than others. Difficult
social
conditions Scapegoating of a less powerful group Negative evaluation & dehumanisation of the target group Moral values and rules become inapplicable and the killing begins. The passivity of bystanders (e.g. the UN) enhances the process. Evaluation Research support Gender bias Real world application Reductionism Archer analysed the results of 230 males over 5 studies and found a low positive correlation between testosterone and aggression. However, the participant, and the form and measurement of aggression, differed substantially between studies.

Book et al's meta-analysis of 45 studies established a mean correlation of 0.14 between tesosterone and aggression, although Archer et al claims that methodological problems with this study meant that a correlation of 0.08 was more appropriate. Statistics suggest a sharp increase in gun-related crime in the UK, but why does the presence of guns in the environment lead to increased aggression? Perhaps the presence of a stimulus, such as a gun or knife, triggers increases in testosterone levels (the gun is seen as a threat), which in turn increases aggressive behaviour, a chain of events that would be predicted by the challenge hypothesis.

To test this, Klimesmith et al had male college students provide a saliva sample (to measure testosterone), interact either with a gun or a child's toy for 15 minutes, and then provide another saliva sample. Males who interacted with the gun showed significantly greater increases in testosterone and behaved more aggressively toward another participant compared to those who played with the child's toy. Most studies concerned with testosterone and aggression have involved male participants, but does testosterone increase aggression in females?

Archer et al- If anything, research suggests that the association between testosterone and aggression is higher for female than male samples.

Baucom et al- Women with higher testosterone levels had higher occupational status, possibly as a result of being more assertive.

These studies indicate that women may also respond to challenging situations with increased testosterone, displaying characteristics such as aggressiveness and dominance.

Eisenegger et al- Testosterone could make women act "nicer" rather than more aggressively, depending on the situation. This lends support to the idea that, rather than directly increasing aggression, testosterone promotes status-seeking behaviour of which aggression is one type. The links between biological mechanisms such as serotonin and tesosterone with aggression are not as well-established in humans as they are in non-human animals.

This is not to deny that such links exist, but rather that the complexity of human social behaviour means that a biological explanation for human aggression is insufficient on its own to explain all the many different aspects of aggressive and violet behaviour. Evaluation Problems of sampling Real world application The value of animal research Many of the studies in this area have focused on individuals convicted of violent crime. 2 particular difficulties arise when trying to draw meaningful conclusions from these studies.

1-Convictions for violent crime are relatively few compared to the vast number of violent attacks by individuals that never result in a conviction. Participants therefore represent just a small minority of those regularly involved in aggressive behaviour.

2- Contrary to popular belief, offenders designated as "violent" on the basis of a court conviction are not necessarily the most serious, persistent offenders. E.g. a convicted murderer would be designated as violent for one offence despite, perhaps, having otherwise had a lifetime free from crime. This might explain why so many studies have found little or no evidence fo heritability for violence. Studies of aggressive behaviour in non-human animals have an important role in helping us understand aggressive behaviour in humans. For example, rodents offer the advantage of experimental manipulation to test the effects of specific genes on aggressive behaviour. Manipulations may involve selective breeding programmes and "knockout" techniques (where a single gene is eliminated from a group of experimental animals in order to study its effect).

An example of such a study that has potential for an understanding of human aggression was by Young et al. These researchers claim to have identified a genetic mutation that causes violent behaviour in mice. This mutation, nicknamed "fierce", has a range of effects on mice, including extremely violent behaviour towards other mice. A counterpart of this gene does exist in humans, although its precise function is not known. Although studies of the biological basis of aggression interest nearly everyone, research findings are far too uncertain to be valuable in understanding the causal factors affecting those who engage in violent activities. Nevertheless there have been suggestions that public policy should be informed by the results of this research. If people are predisposed towards aggressive behaviour or violent crime, then questions about the treatment of such behaviours inevitably arise.

Some commentators advocate genetic engineering but others go much further. As long as violence remains at the forefront of public concern, ways of dealing with it that address the problem more directly remain an attractive option to many.
Given the extremely tentative nature of conclusions that can be reached from this research and the far-reaching ethical consequences of labelling an individual as a threat to society on the basis of their genetic inheritance, an awareness of the limitations of these studies is extremely important. Jealousy & extreme violence Daly et al- Male sexual jealousy is claimed to be the single most common motivation for killings in domestic disputes in the US.

Dell- Sexual jealousy accounted for 17% of all cases of murder in the UK.

Men are predominantly the perpetrators, and the threat to their mate is usually the victim.

A summary of 8 studies of same-sex killings involving "love triangles" found that 92% were male-male murders and only 8% were female-female murders. Evaluation Research support Physiological basis Practical applications The predictions concerning mate retention techniques and female-directed violence have been tested in a study by Shackelford et al. This study shows a clear relationship between sexual jealousy, mate-retention strategies by males, and biolence towards women.

Other research also supports this connection. Buss and Shackelford found that men who suspected that their wives might be unfaithful over the next year exacted greater punishment for a known or suspected infidelity than men who did not anticipate future infidelities.

This finding is consistent with the claim in evolutionary psychology that mate retention strategies are evoked only when a particular adaptive problem is faced, in this case the belief that the wife's infidelity is likely. An important implication of research such as Shackelford et al's is that particular tactics of mate retention used by males can be an early indicator of violence against the female partner.

The findings from these studies can potentially be used to alert friends and family members to the danger signs, the specific acts that can lead to future violence in relationships. At this point, help can be sought or offered before the violence ever happens. The claim that male sexual jealousy is linked to aggression is supported in a study by Takahashi et al.

They showed that the neural response to imagined scenes depicting sexual infidelity (e.g. their partner having sex) and emotional jealousy (e.g. their partner falling in love) was different for men and women.

Using brain imaging techniques, they discovered that men showed greater activation in the amygdala and hypothalamus (brain areas associated with aggression), when presented with scenes depicting sexual infidelity in their mate. Limited understanding Edlund and Sagarin claim that our understanding of the relationship between sexual jealousy and aggression is limited.

For example, research doesn't tell us whether the perceived locus of responsibility (e.g. whether the perceived infidelity is initiated by the female partner or the male rival) moderates the jealous response.

Nor does research tell us whether the degree of perceived infidelity is important (e.g. whether sexual intercourse provokes a greater degree of jealousy than some other action). Problems with surveys Infidelity Infidelity Pregnant partners & violence Sexual coercion Another problem linked to mate violence is sexual infidelity- i.e. voluntary sexual relations between an individual who is married and someone who is not the individual's spouse.

Daly et al- Research suggests that the detection or suspicion of infidelity is a key predictor of partner violence.

Although a BBC online survey found that men are more likely to engage in extra-marital affairs than women, it also discovered that one in 10 women admitted to being unfaithful to their husbands. Goetz et al- A consequence of men's perceptions or suspicions of their wives' sexual infidelity is sexual coercion or partner rape.

Camilleri- Found that sexual assault of a female by her male partner was directly linked with the perceived risk of her infidelity.

Shields & Hanneke- Found that female victims of partner rape were more likely to have reported engaging in extra-marital sex than woman who had not been raped by their male partner. Sexual infidelity by a woman may sometimes lead to pregnany

From the perspective of her long-term mate, if the child is born, he risks investing in the offspring of another male and consequently lowering his own reproductive success.

When a woman becomes pregnant with another man's child, the function of violence directed towards her may be to terminate the pregnancy. This eliminates the potential offspring of a rival and leaves the woman free to bear offspring for him. Uxorocide (wife killing) Men can guard against their partner's infidelity either by conferring benefits or by inflicting costs, including violence.

Shackelford et al- As not all men possess resources that might be used to provide benefits, some men are especially prone to using violence, or the threat of violence.

Daly & Wilson- Death of the partner from physical violence may be an unintended outcome of an evolutionary adaptation that was designed for control rather than death. Evaluation Research support Limitations Pregnant partners & violence The link between infidelity and partner violence is supported by Camilleri's finding that the risk of a partner's infidelity predicts sexual coercion among males, but not among females.
This is significant because males, but not females, are at risk of cuckoldry, i.e. unwittingly investing resources in genetically unrelated offspring.

Camilleri & Quinsey found that men convicted of raping their partners were more likely to have experienced cuckoldry risks prior to their offence than men convicted of non-sexual partner abuse. There is some supporting evidence for the hypothesis that a man who suspects his partner is pregnant with another man's child is likely to inflict violence upon her.

Burch & Gallup found that the frequency of violent acts towards pregnant mates was roughly double the frequency of violent acts directed towards partners who were not pregnant. Sexual jealousy characterised the men who committed violence against their pregnant partners.

Taillieu & Brownridge found that women abused while pregnant were more likely to be carrying the child of a man other than her current mate.

Valladares et al found that half of a sample of pregnant women physically abused by their partners had suffered from blows directed at their abdomen, specifically designed to increase the probability of aboring the foetus. An evolutionary perspective on violence cannot explain why people react in different ways when faced with the same adaptive problem.

Buss & Shackelford suggest that an evolutionary perspective on violence cannot account for why different males, when faced with their partner's infidelity, respond in different ways.

Some men may resort to aggressive mate-retention strategies, others to murder and others to get drunk. Most studies of infidelity have focused solely on men's mate retention strategies and men's violence against women.

However, women also engage in mate retention tactics and sometimes behave violently towards their partners.

Research suggests that women initiate and carry out physical assaults on their partners as often as men do.

For example, Felson examined 2060 murders in the US and found that women were twice as likely to murder out of jealousy than men. Gender bias War Sexual selection Signals of commitment Status within a group Evaluation In societies that experience frequent warfare, males are far more likely to escape infanticide than females because of their potential usefulness in batte. As a result, since there are relatively few women compared to men in these societies, men must compete with each other for mates, with those who do well in battle being "rewarded" by access to female mates (Divale & Harris).

Displays of aggressiveness and bravery are attractive to females, and their absence reduces the attractiveness of individual males. For example, male warriors in traditional societies tend to have more sexual partners and more children, suggesting a direct reproductive benefit (Chagnon).

Palmer & Tilley found that male youth street gang members have more sexual partners than ordinary young males.

Leunissen & Van Vugt found that military men have greater sex appeal but only if they have been observed showing bravery in combat. Displays of ferocity and aggressiveness by individual warriors would also lead peers to respect them more and so strengthen the bond between them and other males in the group.

Because cooperation between males is so important to an individual's status in the group, fleeing from battle woud make an individual appear a "coward", thus losing the respect of their peers.

According to this perspective, displays of aggressiveness & bravery in battle means that individuals are more ikely to share the benefits associated with status, which in turn woud increase their reproductive fitness. Anthropologists suggest that one of the primary functions of ritual displays is the promotion of group solidarity, particularly in times of collective action.
Irons claims that the costliness of permanent displays such as scars and mutilation means that they serve as honest signals of commitment to the group.

By engaging in such displays, individuals demonstrate their commitment and loyalty to the group and so can benefit from the profits of warfare against another group.

During battle, each individual has an incentive to keep himself out of harm's way which, as a result, exposes others to a greater risk of injury or death.
Therefore, in groups where war against other groups is relatively frequent, displays such as permanent scars or piercings would be important for the survival of the group. Tihs is because such permanent displays minimise the abiity of males to abscond to another group & increase their commitment to the group of which they are a member. War emerged when humans shifted from a nomadic existence to a settled one and were tied to agriculture or fishing sites. Because of this, people could no longer walk away from trouble and had far more to lose, and to fight over, than the hunter-gatherers before them. So rather than being an evolved adaptation, it looks as if warfare emerged as a rational response to a changing lifestyle. This suggests warfare, and the aggressive displays associated with warfare, are not biological compulsions but are a consequence of environmenta changes, such as rising populations & dwindling food supplies. (LeBlanc & Register).

Explanations of displays of aggression that are based on mating success, status or commitment fail to explain the astonishing levels of cruelty that are often found in human wars yet not among non-human species. Humans, unlike non-human animals, torture and mutiliate their opponents when they have already been defeated and no longer pose a threat. Anthropological evidence (e.g. Watson) suggests this may be more a consequence of deindividuation effects than of evolutionary adaptations. Foldesi provides evidence to support the link between xenophobia and violent displays among Hungarian football crowds.

He found that the racist conduct of a core of extremist supporters led to an increase of spectators' violence in general, and xenophobic outbursts in particuliar.

Violent incidents based on racist of xenophobic attitudes were observed at all stadia, with gypsies, Jews and Russians the usual targets.

Podaliri & Balestri analysed group displays of Italian football crowds, finding evidence of xenophobic tendencies. Another explanation for the evolution of group displays in sport is based on territoriality, the protective response to an invasion of one's territory.

Territorial behaviour is common in many animal species, which typically show threat displays toward outsiders and attack with greater vigour when defending a home territory (Huntingford & Turner). This form of territorial display has its human equivalent in the aggressive displays of sports teams prior to a match- e.g. rugby teams adopting war chants before a World Cup. These displays intimidate opponents and make the home team more aggressive towards them.

Aggressive displays would have been adaptive for our distant ancestors because they allowed groups to defend valuable resources associated with their territory. Neave and Wolfson found that football teams playing at home were far more likely to win than the visiting team partly because players have the benefit of a huge surge in testosterone before a match.

They believed this could be due to an evolved drive to defend home territory, which led to more aggressive displays when playing at home. This increase in testosterone levels before home games (compared with levels before training) did not occur before away games.

Team members who subjectively felt that the burden of "defending the territory" lay with them (e.g. goalkeepers) had higher levels of testosterone compared to other players. Is there a home advantage? Lewis et al found that among football fans, crowd support was rated as the most significant factor contributing to a home advantage. Through their displays of support, fans felt responsible for inspiring their team to victory and took credit for distracting opponents.

However, the precise way in which displays of support have an effect has been difficult to pinpoint. For example, the relationship with crowd size is unclear as the advantage has been shown to operate even with very small crowds (Pollard & Pollard).

Likewise, it is not known whether the primary effect of crowd displays is to "psych up" the home team or distract the away team, all of which suggests that the original adaptive function of such displays may no longer be relevant.

Moore & Brylinsky analysed a number of basketball games by 2 teams. Both were found to have a better average score when spectators were not present. This suggests that the displays of support from home crowds do not increase the performance of teams. Evolutionary expanations for warfare may demonstrate a gender bias as they do not adequatey reflect the behaviour of women in this process.

Adams claimed that the idea of a woman warrior is almost unheard of within most societies. Even within those societies that allow women to participate in war, women are always the rare exception.

Women would have considerably less to gain from fighting in near-death situations and considerably more to lose (in terms of loss of their reproductive capacity). This is fundamental to women's exclusion from warfare, as women simpy do not increase their fitness as much as men do.

Our understanding of the displays typically found in warfare is therefore imited to the behaviour of males rather than females. Gender bias
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