Psychology - Aggression

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Social Learning Theory

SLT

  • suggests we learn by observing others
  • we learn the specifics of aggressive behaviour (form it takes, how often it is enacted, situations that produce it, targets towards which it is directed)
  • doesn't suggest the role of biological factors is ignored in this theory, rather a person's biological make up creates a potential for aggression and it is the expression of aggression that is learned
  • Bandura et al's classic study illustrates many important principles of this theory

The bobo doll studies 

  • Research support for predictions of SLT comes from a series of studies carried out by Albert Bandura and colleagues
  • Experiment by Bandura et al (1961) 
  • involved children observing aggressive and non-aggressive adult models
  • then were tested for imitative learning in the absence of the model
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Social Learning Theory

The bobo doll studies

  • The participants were male and female children, ranging from 3-5 years
  • 1/2 were exposed to adult models interacting aggressively with life sized inflatable Bobo dol
  • half exposed to models that were non-aggressive towards the doll
  • model displayed distinctive physically aggressive acts towards the doll e.g striking it on the head with the mallet/kicking it about the room
  • was accompanied by verbal aggression
  • following exposure to the model, children were frustrated by being shown attractive toys which tey were not allowed to play with
  • were then taken to a room where among other toys, there was a Bobo doll
  • children in the aggression conditiong reproduced a good deal of physically and verbally aggressive behaviour resembling that of the model
  • children in non-aggressive group exhibited virtually no aggression toward the doll
  • 1/3 of the children in aggressive condition repeated model's verbal responses
  • none of the children in non-aggrssive group made such remarks
  • boys reproduced more imitative physical aggression than girls
  • did not differ in their imitating of verbal aggression
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Social Learning Theory

Observation

  • Children primarily learn their aggressive responses through observation
  • watch the behaviour of role models and then imitate the behaviour
  • Skinner's operant conditioning theory claimed learning takes place through direct reinforcement
  • Bandura suggested children learn by observing role models with whom they identify
  • children also observe and learn about consequences of aggressive behaviour by watching others being reinforced or punished
  • called indirect or viarious reinforcement
  • children witness many examples of aggressive behaviour at home and at school, as well as on television and in films
  • by observing consequences of aggressive behaviour for those who use it, child gradually learns something about what is considered appropriate conduct in the world around them
  • they learn the behaviours (through observation) and also learn whether and when such behaviours are worth repeating (through vicarious reinforcement)
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Social Learning Theory

Mental representation

  • Bandura claimed that in order for social learning to take place, child must form mental representations of events in their social environment
  • child must also represent possible rewards and punishments for aggressive behaviour in terms of expectancies of future outcomes
  • when appropriate opportunities arise in the future, child will display learned behaviour as long as the expectation of reward is greater than expectation of punishment

Production of behaviour

Maintenance through direct experience

  • If a child is rewarded for a behaviour, he or she is likely to repeat the same action in similar situations in the future
  • child who has a history of successfuly bullying other children will therefore come to attach considerable value to aggression

Self efficacy expectancies

  • children develop confidence in their ability to carry out the necessary aggressive actions
  • children for whom this form of behaviour has been particularly disastrous in the past have less confidence
  • have lower sense of self-efficacy in their ability to use aggression successfully to resolve conflicts and therefore may turn to other means
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Social Learning Theory

Evaluation

Research support

Role of punishment

  • Bandura repeated the study but this time, after exposure to the model, offered rewards to all children for performing the model's aggressive behaviours
  • in this case, all 3 groups performed a similar number of imitative acts
  • shows learning does take place regardless of reinforcement but that production of behaviours is related to selective reinforcements

Applicability to adults

  • studies mainly have involved children, SLT can explain adult behaviour as well 
  • Philips (1986) found daily homicide rates in US almost always increased in the week following a major boxing match 
  • suggests viewers were imitating behaviours they watched and social learning is evident in adults as well as children
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Social Learning Theory

Evaluation

Strengths

Role of vicarious learning

  • major strength of theory is that unlike operant conditioning, it can explain aggressive behaviour in the absence of direct reinforcement
  • at no point were the children in Bandura's study directly rewarded for any action, either aggressive or non-aggressive
  • consequently, concept of vicarious learning is necessary to explain these findings

Individual differences in aggressive behaviour

  • can explain differences in aggrssive/non-aggressive behaviour between and within individuals
  • culture of violence theory - Wolfgang and Ferracuti
  • propose that in large socieites, some subcultures develop norms that sanction vioence to greater degree than the dominant culture
  • some cultures may emphasise and model non-aggressive behaviour, producing individuals that show low levels of aggrssion
  • differences within individuals can be related to selective reinforcement and context-dependent learning
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Social Learning Theory

Evaluation

Cultural differences

  • SLT can be used to explain cultural differrenes in aggression
  • among the Kung San of Kalahari Desert, aggression is comparatively rare
  • child rearing practices of the Kung San provide answers
  • when two children argue/fight, parents neither reward them nor punish them
  • separate them and try to distract their attention onto other things
  • parents do not use physical punishment
  • aggrssive postured are avoided by adults and devalued by the society as a whole
  • absense of direct reinforcement of aggressive behaviour as well as absence of aggressive role models means there's little opportunity or motivation for Kung San children to acquire aggressive behaviouurs
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Social Learning Theory

Process of deindividuation

  • people normally refrain from acting in an aggressive manner partly because they are social norms inhibiting 'uncivilised' behaviour and partly because they are easily identifiable
  • being anonymous in a crowd has the psychological consequence of reducing inner restraints and increasing behaviours that are usually 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 group the larger the anonymity
  • there is diminished fear of negative evaluation of actions and reduced sense of guilt
  • conditions that increase anonymity also minimise concerns about evaluation by others
  • this weakens the normal barriers to antisocial behaviour that are based on guilt or shame
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Social Learning Theory

Process of deindividuation

  • people normally refrain from acting in an aggressive manner partly because they are social norms inhibiting 'uncivilised' behaviour and partly because they are easily identifiable
  • being anonymous in a crowd has the psychological consequence of reducing inner restraints and increasing behaviours that are usually 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 group the larger the anonymity
  • there is diminished fear of negative evaluation of actions and reduced sense of guilt
  • conditions that increase anonymity also minimise concerns about evaluation by others
  • this weakens the normal barriers to antisocial behaviour that are based on guilt or shame
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Deinviduation

Deinviduation theory

  • Deinviduation theory is based on the classic crowd theory of Gustave Le Bon
  • Described how an individual was transformed when part of a crowd
  • claimed that, in a crowd, combination of anonymity, suggestibility and contagion mean that a 'collective mind' takes possession of the individual
  • as a consequence, individual loses self control and becomes capable of acting in a way that goes against personal/social norms

Nature of deinviduation

  • deinviduation is a psycological state characterised by lowered self-evaluation and decreased concerns  about evaluation by others
  • leads to an increase in behaviour that would normally be inhibited by personal or social norms
  • psychological state of deindividuation is aroused when individuals join crowds or large groups
  • factors that contribute to deindividuation include anonymity and altered consciousness due to drugs or alcohol
  • Zimbardo has stressed that these same conditions may also lead to an increase in prosocial behaviours
  • focus of deindividuation theory has almost been exclusively on antisocial behaviour
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Deinviduation

Process of deindividuation

  • People normally refrain from acting in an aggressive manner because there are social norms inhibiting such 'uncivilised' behaviour
  • partly also becaue they are easily identifiable
  • being anonymous in a crowd has the psychological consequence of reducing inner restraints and increasing behaviours that are usually inhibited
  • According to Zimbardo being part of a crowd can diminsh awareness of our own individuality
  • in large crowd, each person is faceless and anonymous 
  • the larger the grou pthe larger the anonymity
  • there is diminished fear of negative evaluation of actions and reduced sense of guilt
  • conditions that increase anonymity also minimise concerns about evaluation by others
  • this weakens the normal barriers to antisocial behaviou that are based on guilt or shame
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Deinviduation

Research deinviduation

  • Anonymity (Zimbardo) 1969
  • Provideded support for the link between deindividuation and increased aggression 
  • groups of four female under-graduates 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
  • other participants wore normal lothes and were given large nae tags to wear and were introduced to each other by name
  • were also able to see eah other when seated at shock machines
  • both sets of participants were told they could see the person being shocked
  • participants in the deindivudation condition (hooded and no name tags) shocked the learner for twice as long as the identifiable participants
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Deinviduation

Research on deindividuation

Anonymity

  • Zimbardo carried out a series of experiments that were instrumental in the development of deindividuation theory
  • one of these was described on the previous card
  • study led to the suggestion that anonymity is a key component in the deindividuation process and increases aggressiveness
  • Rehm et al (1987) invstigated whether wearing a uniform when part of a sports team also increased aggressive behaviour 
  • randomly assigned German schoolchildren to handball teams of 5 people
  • half the teams wore the same orange shirts, other half wore their normal street clothes
  • children wearing orange (who were harder to tell apart) played the game consistently more aggressively than the children in their everyday clothes

The faceless crowd

  • Mullen (1986) analysed newspaper cuttings of 60 lynchings in the US between 1899-1946
  • Found the more people there were in the mob, the greater the savagery with which they killed their victims
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Deinviduation

Reduced private self-awareness

  • Prentice-Dunn et al (1982) offer alternative perspective to Zimbardo's conclusion anonymity is an important determinant of deindividuation
  • they claim that reduced-self awarenesss, rather than simply anonymity, leads to deindividuation
  • if an individual is self-focused, they tend to focus on, and act according to, their internalised attitudes and moral standards
  • this reduces the likelihood of antisocial behaviour
  • if individual submerges themselevs within a group, may lose this focus and become less privately self aware
  • therefore, they are less able to regulate their own behaviour
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Deinviduation

Evaluation

Importance of local group norms

  • Johnson and Downing (1979) explored the idea that rather than deindividuation automatically increasing the incidence of aggression, any behaviour produced could be a product of local group norms
  • used the same experimental conditions as Zimbardo
  • this time, participants were made anonymous by means of a mask and overalls (reminiscent of the KKK) or by nurse's uniforms
  • participants shocked more than a control condition when dressed in KKK uniforms but 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
  • participants dressed as KKK klansmen clearly fel that aggressive behaviour was more appropriate than those dressed as nurses
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Deinviduation

Evaluation

Lack of support for deindividuation

  • evidence for deindividuation theory is mixed
  • Meta-analysis of 60 studies of deindividuation (Postmes and Spears 1998) concludes there's insufficient support for the major claims of deindividuation theory
  • found that disinhibition and antisocial behaviour are not more common in large groups and anonymous settings
  • there was not much evidence that deindivuation is associated with reduced self-awareness, or that reduced self-awareness increases aggressive behaviour

Prosocial consequences of deindividuation

Deindividuation can increase prosocial behaviour

  • some studies have shown that deindividuationn may increase the incidence of prosocial behaviour
  • Spivey and Prentice-Dunn (1990) found deindividuation could lead to prosocial or antisocial behaviour depending on situational factors
  • when prosocial environemntal cues were present, deindivuated participants performed significantly more altruistic acts and significantly fewer antisocial acts compared to a control group
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Deinviduation

Cultural differences

  • dramatic support for the deadly influence of deindividuation comes from a study by anthropologist Robert Watson (1973)
  • 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
  • those societies where warriors changed their appearance were more destructive towards their victims compared to those who did not change their appearance
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Institutional Aggression

Aggression within groups: Prisons

The importation model

Interpersonal factors

  • Irwin and Cressey (1962) claim prisoners bring their own social histories and traits with them into prison
  • this influeences their adaptation to the prison environment
  • Irwin and Cressey argue that prisoners are not 'blank slates' when they enter prison
  • many of the normative systems developed on the outside would be 'imported' into the prison

Gang membership

  • Within prison environments, gang membership is consistently related to violence and other forms of antisocial behaviour 
  • Several studies have found that gang members disproportionately engage in acts of prison violence
  • pre-preison gang membership appears to be an important determinant of prison misconduct
  • members of street gangs offend at higher levels than their non-gang counterparts
  • Huff (1998) found gang members in US were 10x more likely to commit murder and 3x more likely to assault someone in public than non-gang members of similar age/background
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Institutional Aggression

Situational factors - the 'deprivation model'

  • model argues prisoner/patient aggression is the product of the stressful and oppressive conditions of the institution itself
  • These include crowding, assumed to increase fear and frustrational levels
  • Hodgkinson et al (1985) found trainee nurses are more likely to suffer violent assault than experienced nurses
  • in the prison like setting, length of service was also a significant factor, with more experienced officers being less likely to suffer an assault (Davies and Burgess 1988)

The 'pains of imprisonment'

  • Skyes (1958) described specific deprivations that inmates experience within prison and which might be liked to an increase in violence
  • included loss of liberty, loss of autonomy and loss of security
  • Found that the potential threat to personal security increased anxiety levels in inmates, even if majority of prisoners posed no significant threat to them
  • inmates may cope with the pains of imprisonment in several ways
  • some choose to withdraw through seclusion in their cell or living space
  • others choose to rebel in the form of violence against other prisoners or staff
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Institutional Aggression

Obedience to authority

  • Mandel (1998) rejects Milgram's claims that obedience to authrotuy was sufficient to explain the behaviour of Holocaust perpetrators
  • Argues Milgram's account is monocausal and simply does not match the historical record
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Institutional Aggression

Institutional aggression between groups: Genocide

Dehumanisation

  • although humans usually have moral inhibitions about killing fellow humans, this changes if the target group is dehumanised
  • it sees members as worthless animals and therefore not worthy of moral consideration

Obedience to authority

  • Milgram believed the Holocaust was primarily the result of situational pressures that forced Nazi soldiers to obey their leaders regardless of any personal moral repugnance
  • argued that if so many participants in his study could administer painful electric shocks simply because they were told to do so by someone in authority, the Nazi regime would have no trouble making soldiers kill innocent, unarmed people


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Institutional Aggression

Evaluation

Institutional aggression within groups

Importation model

  • Has received some research support, particularly in terms of individual factors, such as age, education level and race
  • Harer and Steffenmeiser (2006)
  • collected data from 58 US prisons
  • found black inmates had signifcantly higher rates of violent behaviour but lower rates of alcohol related and drug related misconduct than white inmates

Gang membership

  • DeLisi et al (2004) challenges claim that pre-prison gang membership predicts violence whilst in prison
  • found inmates with prior street gang involvement were no more likely than other inmates to engage in prison violence
  • lack of a correlation betwen the two might be explained by fact violent gang members tend to be isolated from the general inmate population
  • therefore their opportunities for violence are restricted
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Institutional Aggression

Evaluation

Deprivation model

  • McCorkle et al (1995) found overcrowding, lack of privacy and lack of meaningful activity all influence peer violence
  • research in this area is not consistent in its findings
  • Research in psychiatric institutions for example Nijman et al (1999) found increased personal space failed to decrease level of violent incidents among patients

Institutional aggression between groups: genocide

Dehumanisation

  • Evidence for destructive consequences of dehumanisation can be seen in many conflicts (Jews in Holocaust, Bosnians in Balkan wars, Tutsis in Rwanda)
  • Dehumanisation may also explian violence vs immigrants, seen by some as 'polluting threats to the social order' (O'Brien 2003)
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Neural and hormonal mechanisms in aggression

Neutrotransmitters

  • chemicals that enable impulses within the brain to be transmitted from one area of the brain to another
  • some evidence at least 2 of these neutoransmitters, serotonin and dopamine are linked to aggressive behaviour
  • serotonin and dopamine are of partiular interest because low levels of serotonin and high levels of dopamine have been associated with aggression in animals and humans

Serotonin

  • Thought to reduce aggression by inhibiting responses to emotional stimuli might lead to an aggressive response
  • low levels of serotonin in brain have been associated with an increased susceptibility to impulsive behaviour, aggression and violent suicide
  • some drugs are thought to alter serotonin levels and increase aggressive behaviour
  • Mann et al (1990) gave 35 healthy subjects dexfenfluramine which is known to deplete serotonin
  • using a questionnaire to assess hostility and aggrssion levels
  • found dexfenfluramine treatment in males (not females) was associated with an increase in hostility and aggression scores
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Neural and hormonal mechanisms in aggression

Dopamine

  • Link between high levels of dopamine and aggressive behaviour is not as well established as serotonin
  • there's some evidence to suggest that such a link still exists
  • increases in dopamine through the use of amphetamines have been associated with increases in aggressive behaviour (Lavine 1997)
  • antipsychotics, which reduce dopamine activity in the brain have been shown to reduce aggressive behaviour in violent delinuqnets (Buitelaar 2003)

Hormonal mechanisms

Testosterone

  • Male sex hormone testosterone thought to influence aggression from young adulthood onwards due to its action on brain areas involved in controlling aggression
  • evidence for this association comes from a number of sources
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Neural and hormonal mechanisms in aggression

Hormonal mechanisms

Research studies

  • Dabbs et al (1987) measured salivary testosterone in violent and non-violent criminals
  • those with highest testosterone levels had a history of primarily violent crimes, whereas those with lowest levels had committed only non-violent crimes
  • studies of non-prison populations have found similar trends
  • Lindman et al (1987) found young males who behaved aggressively when drunk had higher testosterone levels that those who did not act aggressively

The challenge hypothesis

  • Wingfield et al (1990) proposed that in monagamous species, testosterone levels should only rise above the baseline breeding level in response to social challenges such as male-male aggression or threats to status
  • as human species is considered to be monogamous, this would predict that male testosterone levels would rise sharply in response to such challenges
  • testosterone surge is to be expected in such situations with consequent increase in aggression
  • this is provided the threat is deemed relevant to reproductive competition, e.g dispute over a female
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Neural and hormonal mechanisms in aggression

Cortisol

  • Appears to have mediating effect on other aggression-related hormones such as testosterone
  • it possibly increases anxiety and the likelihood of social withdrawal (Dabbs et al)
  • high levels of cortisol inhibit testosterone levels and so inhibit aggression
  • Studies have reported low levels of cortisol in habitual violent offenders (Virkkunen 1985) and in violent schoolchildren (Tennes and Kreye 1985)
  • suggests that although high testosterone is the primary biochemical influence on aggression, low cortisol plays an important role in increasing the likelihood of aggressive behaviour

Evaluation

Serotonin

Evidence from non-human studies

  • Raleigh et al (1991) have added support for the importance of serotonin in aggressive behaviour in a study of vervet monkeys
  • found individuals fed on experimental diets high in tryptophan exhibited decreased levels of aggression
  • individuals fed on diets low in tryptophan exhibited increased aggressive behaviour
  • suggests difference in aggression could be attributed to their serotonin levels
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Neural and hormonal mechanisms in aggression

Evaluation

Serotonin

Evidence from antidepressants

  • if low levels of serotonin are associated with llow impulse control and aggressive behaviour, drugs that clinically raise serotonin levels should produce a concurent lowering in aggression
  • Bond (2005) has established that this is exactly what happens in clinical studies of antidepressant drugs that elevate serotonin levels
  • Established that such drugs do tend to reduce irritability and impulsive aggression

Dopamine

  • research is fairly inconclusive about the causal role of dopamine in aggression
  • recent research suggests that its influence might be as a consequence instead
  • Couppis and Kennedy (2008) 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
  • suggests individuals will intentionaly seek out an aggressive encounter solely because they experience a rewarding sensation from it
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Neural and hormonal mechanisms in aggression

Hormonal mechanisms

Evaluation

Testosterone

Inconsistent evidence

  • Albert et al (1993) claim that despite many studies showing a positive correlation between testosterone and aggression, other studies find no such relationship
  • in particular, 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
  • used either self-report measures of aggression or judgements based solely on the severity of the crime committed 
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Neural and hormonal mechanisms in aggression

Hormonal mechanisms

Evaluation

Aggression or dominance? 

  • Mazur (1985) suggests we should distinguish aggression from dominance
  • individuals act aggressively when their intent is to inflict injury, whereas act dominantly if their wish is to achieve or maintain status over another
  • Claims aggression is just one form of dominance behaviour
  • non-human animals, influence of testosterone on dominance behaviour might be shown in aggressive behaviour
  • in humans, influence of testosterone on dominance is likely to be expressed in more varied and subtle ways

Cortisol

  • moderating effect of cortisol on aggressive behaviour is suported in a 4 year study of boys with behavioural problems (McBurnett et al 2000)
  • boys with consistently low levels of cortisol began antisocial acts at a younger age 
  • exhibited 3 times the number of aggressive symptoms compared to boys with higher or fluctating cortisol levels
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Genetic factors in aggression

Twin studies

  • Monozygotic (identical) twins share all of their genes
  • Dizygotic (non-identical) twins share only 50%
  • in twin studies, researchers compare the degree of similarity for a particular trait (such as aggression) between sets of MZ twins to the similarity between sets of DZ twins
  • if MZ twins are more alike in terms of their aggressive behaviour, this should be due to genes rather than environment
  • most twin studies have focused on criminal behaviour generally
  • 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 (i.e aggression towards others) could be attributed to genetic factors (Coccaro et al 1997)
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Genetic factors in aggression

A gene for aggression?

Role of MAOA

  • no individual gene for aggression has been identified in humans
  • gene responsible for producing a protein called monoamine oxidase A (MAOA) has been associated with aggrssive behaviour
  • MAOA regulates metbolism of serotonin in the brain 
  • low levels of serotonin are associated with impulsive and aggressive behaviour
  • 1980s - study of a Dutch family found that many of its male members behaved in a particularly violent and aggressive manner
  • large proportion had been involved in serious crimes of violence, including **** and arson
  • men were found to have abnormally LOW levels of MAOA in their bodies
  • a defect in this gene was later identified (Brunner et al 1993)

Gene-environment interaction

  • second study (Caspi et al 2002) linked MAOA to aggressive behaviour
  • involed 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 - significantly more likely to grow up to exhibit antisocial behaviour only if they had been maltreated as children
  • children with high levels who were maltreated, and those with low levels who were not maltreated, did not display antisocial behaviour
  • shows that it is the interaction between genes and environment that determines behaviours, such as aggression
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Genetic factors in aggression

Adoption studies

  • can help untangle the relative contributions of environment and heredity in aggression
  • if a positive correlation is found between aggressive behaviour in adoped children and aggrsesive behaviour in biological parents, a genetic effect is implied
  • if a positive correlation is found between adoptee's aggressive behaviour and the rearing family, an environmental effect is implied
  • study of over 14,000 adoptions in Denmark found a significant number of adopted boys with criminal convinctions had biological parents(particularly fathers) with criminal convinctions
  • (Hutching and Mednick)
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Genetic factors in aggression

Genetics and violent crime

  • researchers do not suggest there is a gene for violent crime per se
  • Rather it is claimed that inherited temperamental or personality characteristics place some individuals more at risk of commiting violent crime
  • adoption studies have shown that the highest rates of criminal violence in adopted children occured when both biological and adoptive parents have a history of violent crime
  • this is clear evidence of a gene-environment interaction 
  • a series of adoption studies in which the criminal history of an adopted male was compared with the criminal history of both his biological and his adoption fathers 
  • found that genetic influences were significant in cases of property crime but not in casse of violent crime (Brennan and Mednick 1993)
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Genetic factors in aggression

Genetics and violent crime

  • researchers do not suggest there is a gene for violent crime per se
  • Rather it is claimed that inherited temperamental or personality characteristics place some individuals more at risk of commiting violent crime
  • adoption studies have shown that the highest rates of criminal violence in adopted children occured when both biological and adoptive parents have a history of violent crime
  • this is clear evidence of a gene-environment interaction 
  • a series of adoption studies in which the criminal history of an adopted male was compared with the criminal history of both his biological and his adoption fathers 
  • found that genetic influences were significant in cases of property crime but not in casse of violent crime (Brennan and Mednick 1993)
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Genetic factors in aggression

Evaluation

Difficulties of determining the role of genetic factors

  • Connection between genetic factors and aggression is far from straight forward
  • difficult to determine what is and what isn;'t a product of genetic inheritance
  • difficult to establish genetic contributions to aggressive behaviour for following reasons
  • more than 1 gene usually contributes to a given behaviour
  • as well as genetic factors there are many non-genetic (environmental) influences on the manifestation of aggressive behaviour
  • influences may interact with each other
  • genetic factors may affect which environmental factors have an influence and vice versa

Problems of assessing aggression

  • many of reported studies of aggression have relied either on parental or self-reports of aggressive behaviour
  • other studies have made use of observational techniques
  • Miles and Carey meta-analysis, mode of assessment was found to be a significant moderator of aggressive behaviour in the 24  studies that made up their analysis
  • found genetic factors explained a large proportion of variance in aggressive behaviour in studies that had used parental/self reports
  • those that had made use of observational ratings showed significantly less genetic contribution and a greater influence of environmental factors
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Genetic factors in aggression

Inheritance of criminal violence

Methodological limitations

  • studies that have investigated the role of genetic factors often fail to distinguish between violent and non-violent crime
  • makes it more difficult to untangle the roe of genetic factors in specifically aggrsesive violence
  • studies also often fail to distinguish between criminals who are habitualy violent and those for whom their violent crime is a one off

Inconclusive evidence

  • evidence for violent crime being inherited is far from conclusive
  • meta-analysis of studies in this area (Walters 1992) found only a low to moderate correlation between heredity and crime
  • better desgiend and more recently published studies provided less support for the gene-crime hypothesis than more poorly designed and earlier published studies
  • more recent review of published studies of youth crime concluded that 'the data does not suggest a strong role for heredity in violence'
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Evolutionary explanations of human aggression

Jealousy

  • Daly and Wilson (1988) claim men have evoved several different strategies to deter female partners from committing adultery 
  • range from vigilance to violence
  • all are fuelled by sexual jealousy
  • this is an adaptation that evolved specifically to deal with the threat of paternal uncertainy

Cuckoldry and sexual jealousy

  • men can never be entirely certain that they are the fathers of their childre, unlike women
  • as a result, men are always at risk of cuckoldry
  • reproductive cost might be inflicted on a man as a result of his partner's infidelity
  • consequence of cuckoldry is that man might unwittingly invest his resources in offspring that are not his own
  • adaptive functions of sexual jealousy would have been to deter a mate from sexual infidelity, therefore minimising the risk of cuckoldry
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Evolutionary explanations of human aggression

Mate retention and violence

  • Buss (1988) suggests males have number of strategies that have evolved specifically for the purpose of keeping a mate
  • include restricting their partners' autonomy and negative inducements in the form of violence or threats of violence to prevent her from straying
  • those who are perceived by their partner to be threatening infedility are more at risk of vioence than those who are not
  • studies of battered women have shown that in majority of cases, women cite extreme jealousy on the part of their husbands or boyfriends as the key cause of violence directed toward them (Dobash and Dobash 1984)

Sexual jealousy and extreme violence

  • male sexual jealousy is claimed to be the single most common motivation for killings in domestic disputes in the US (Daly et al 1982) and Dell (1984)
  • concluded sexual jealousy accounted for 17% of all cases of murder in the UK
  • Men are predominantly the perpetrators and the victims
  • summary of 8 studies of same-sex killings involving 'love triangles' found 92% wre male-male murders and only 8% were female-female murders
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Evolutionary explanations of human aggression

Infidelity

  • 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
  • research suggests the deception or suspicion of infidelity is a key predictor of partner violence (Daly et al 1982)
  • 2006 online survey (The Love Map, BBC 2006) found men are more likely to engage in extra-marital affairs than women
  • also discovered that 1 in 10 women admitted to being unfaithful to their husbands

Sexual coercion

  • consequence of men's perceptions or suspicions of their wives' sexual infidelity is sexual coercion or partner **** (Goetz et al 2008)
  • Camilleri (2004) found sexual assault of a female by her male partner was directly linked with the perceived risk of her infidelity
  • Shields and Hanneke (1983) found that female victims of partner **** were more likely to have reported engaging in extra-marital sex than women who had not been ****d by their male partner
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Evolutionary explanations of human aggression

Violence toward pregnant partners

  • sexual infidelity by a woman may sometimes lead to pregnancy
  • 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, therefore, the function of violence directed towards her may be to terminate the prengancy, thus eliminating the potential offspring of a rival and leaving her 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
  • 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 (Shackelford et al 2000)
  • Daly and Wilson (1988) claimed the death of the partner from physical violence may be an unintended outcome of an evolutionary adaptation that was designed for cotrol rather than death
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Evolutionary explanations of human aggression

Evaluation

Jealousy

Research support

  • predictions concerning mate retention techniques and female-directed violence have been tested in the Shakelford et al study 
  • study shows a clear relationship between sexual jealousy, mate retention strategies by males and violence towards women
  • other research also supports this connection
  • Buss and Sheckelford (1997) found that men who suspected 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
  • finding is consistent with claim in evolutionary psychology that male retention strategies are evoked only when a particular adaptive problem is faced, in this case the belief the wife's infidelity is likely
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Evolutionary explanations of human aggression

Evaluation

Jealousy

Practical applications

  • an important implication of research such as Sheckelford et al's is that particular tactics of mate retention used by males can be an early indicator of violence against a female partner
  • the findings from these studies can potentially be used to alert friends and family members to the danger signs, specific acts can lead to future violence in relationships
  • at this point, help can be sought or offered before the violence ever happens

Physiological basis for jealousy based aggression

  • claim that male sexual jealousy is linked to aggression is supported in a study by Takahashi et al (2006)
  • showed that the neural response to imagined scenes dpicting sexual infidelity and emotional jealousy was different for men and women
  • using brain imaging techniques, they found men showed much greater activation in the amygdala and hypothalamus (brain areas associated with aggression) when presented with scenes depicting sexual infidelity in their mate
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Evolutionary explanations of human aggression

Evaluation

Jealousy

Research doesn't tell whole story

  • Edlund and Sagarin (2009) claim that our understanding of the relationship between sexual jealousy and aggression is limited
  • research doesn't tell us whether the perceived locus of responbility moderates the jealous response
  • nor does research tell us whether the degree of perceived infidelity is important
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Evolutionary explanations of human aggression

Evaluation

Infidelity

Research support

  • link between infidelity and partner violence is supported by the finding that the risk of a partner's infidelity predicts social coercion among males, but not among females (Camilleri 2004)
  • this is significant because males, not females are at risk of cuckoldry
  • in other study supporting this link, Camilleri and Quinsey (2009) found men convicted of ****** their partners were more likely to have experienced cuckoldry risks prior to their offence compared to men convicted of non-sexual partner abuse

Violence toward pregnant partners

  • there is some supporting evidence for hypothesis that a man who suspects his partner is pregnant with another man's child is likely to inflict violence on her
  • Burh and Gallup (2004) found the frequency of vioent acts toward pregnant mates was double that direct toward partners who were not pregnant
  • sexual jealousy characterised those men who committed violence against their pregnant partners
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Evolutionary explanations of human aggression

Evaluation

Infidelity

Limitations of evolutionary explanations of partner violence

  • evolutionary perspective of violence cannot explain why people react in different ways when faced with the same adaptive problem
  • Buss and Sheckelford (1997) suggest it 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 will just get drunk
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Group display as an adaptive response

Sports

Xenophobia

  • Wilson (1975) claims that xenophobia 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 toward members of their own group but intolerant to outsiders
  • Shaw and Wong (1989) 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 (1992) suggests that from an evolutionary perspective, it is adaptive to exaggerate negative stereotypes about outsiders, as the overperception of threat is less constly than its underperception

Xenophobic displays on the terraces

  • Podaliri and Balestri (1998) have found evidence of xenophobic tendencies in their analysis of group displays of Italian football crowds
  • 1980s, xenophobic political organisations such as the Northn League led to growth of extreme right wing movements
  • these were characterised by racist chants and openly anti-Semitic banners
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Group display as an adaptive response

Sports

Territoriality

Threat displays

  • another explanation for the evolution of group displays in sport is based on territoriality
  • protective response to an invasion of one's territoy
  • territorial behaviour is common in many animal species
  • typically show threat displays toward outsiders and atack with greater vigour when defending a home territory
  • this form of territorial display has its human equivalent in aggressive displays of sports teams prior to a match
  • 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
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Group display as an adaptive response

Sports

Territoriality

Testosterone and territorial behaviour

  • animals display more aggression when they have higher testosterone levels
  • Neave and Wolfson (2003) found that football teams playing at home were more likely to win than the away team partly because players have the benefit of a huge surge in testosterone before the match 
  • believed this could be due to an evolved drive to defend home territory, which led to more aggressive displays when playing at home
  • increase in testosterone levels before home games did not occur before away games
  • players who subjectively felt that the burden of 'defending the territory' lay with them, such as goalkeepers, had higher levels of testosterone compared to other players
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Group display as an adaptive response

Warfare

Benefits of aggressive displays

Sexual selection

  • in societies that experience frequent warfare, males are far more likely to escape infanticide than females because of their potential usefulness in battle
  • as a result, 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 acess to female mates (Divale and Harris 1976)
  • displays of aggressiveness and bravery are attractive to females
  • their absence reduces the attractiveness of individual males
  • Male warriors in traditional societies tend to have more sexual partners and more childre, suggesting a direct reproductive benefit (Chagnon 1988)

Acquisition of status within the group

  • displays of ferocity and aggressiveness by individual warriors would lead peers to respect them more and strengthen the bond between them and other males in the group
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Group display as an adaptive response

Costly displays signal commitment

Signals of commitment

  • antropologists suggest that one of the primary functions of ritual displays is the promotion of group solidarity, particularly in times of collective action
  • Irons (2004) claims that the costliness of permanent displays such as scans and mutilation means that they serve as honest signals of commitment to the group
  • by engaging in such displays, individuals demonstrate their commitment and loytalty to the group and so can benefit from the profits of warfare against another group

Minimising the likelihood of defection

  • during battle, each individual has an incentive to keep himself out of harms way
  • as a result, exposes others to a greater risk of injury or death
  • 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
  • this is because permanent displays minimise the ability of males to abscond to another group and increase their commitment to the group of which they are a member (Thorpe 2003)
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Group display as an adaptive response

Evaluation

Sports

Research support for xenophobic displays

  • Foldesi (1996) provides evidence to support link between xenophobia and violent displays among Hungarian football crowds
  • found that the racist conduct of a core of extremist supporters led to an increase of spectator's violence in general, and xenophobic outbursts in particular
  • violent incidents based on racist/xenophobic attitudes were observed by all stadia, with gypsies, Jews and Russians the usual targets

Terrotoriality

  • Lewis et al (2005) found that among football fans, crowd support was rated the most significant factor contributing to home advantage
  • through their displays of support, fans felt responsible for inspiring their team to victory and took credit for distracting opponents
  • the precise way in which displays of support have an effect has been difficult to pinpoint
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Group display as an adaptive response

Evaluation

Warfare

Sexual selection

  • research has provided support for the importance of aggressive displays in determining the sexual attractiveness of male warriors
  • Palmer and Tilley (1995) found that male youth street gang members have more sexual partnres than ordinary young males

War is not 'in the genes'

  • 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
  • rather than being an evolved adaptation, looks as if warfare emerged as a rational response to a changing lifestyle
  • suggests that warfare is not a biological compulsion
  • is a consequence of environmental changes, such as rising populations and dwindling food supplies (LeBlanc and Register 2004)
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Group display as an adaptive response

Evaluation

Warfare

Limitations of an evolutionary explanation of warfare

  • 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
  • e.g why do humans torture or mutilate their opponents when they have already been defeated and no longer pose a threat? 
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Aggression IDAs

SLT

Ethical issues in SLT research

  • ethical issues make it difficult to test SLT 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, experiments such as the Bobo doll would no longer be allowed to take place
  • means that is it difficult to test the experimental hypotheses about the social learning of aggressive behaviour in childre, and consequently difficult to establish the scientific credibility of the theory by this means

Deindiviuation

Gender Bias

  • Cannavale et al (1970) found male and female groups responded differently under deindividuation conditions, reflecting a gender bias in the theory
  • increase in aggrssion was only obtained in the all-male groups
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Aggression IDAs

Neural and hormonal mechanisms in aggression

Reductionism and biological mechanisms

  • links between biological mechanisms such as serotonin and testosterone with aggression are well established in non-human animals
  • position is not so clear in the case of humans
  • this is not to deny that such links exist, rather that the complexity of human social behaviour means a biological explanation of human aggression is insufficient on its own to explain all the many different aspects of aggressive and violent behaviour

Gender bias

  • most studies concerned with testosterone and aggression have involved male participants
  • research suggests that the association between testosterone and aggression is higher for female than male samples (Archer et al 2005)
  • further study showed that women with higher testosterone levels had  higher occupational status and were possibly more assertive as a result (Baucom et al 1985)
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Aggression IDAs

Evolutionary explanations of human aggression

Gender bias

  • most studies of infidelity have focused on men's mate retention strategiges 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 intiate and carry out physical assaults on their partners as often as men do 
  • Felson (1997) examined 2060 murders in the US and found that women were twice as likely to murder out of jealousy as were men
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