Aggression - Paper 3 Flashcards
Paper 3
What are neural mechanisms in aggression?
- The limbic system
- Serotonin
What is the limbic system? (neural)
A set of structures in the brain including: cingulate gyrus, hypothalamus and amygdala. The amygdala has been linked to how humans and animals assess threats in the environment and how they respond emotionally to these threats.
Evidence from fMRI scans have shown that damage or under-activity in the pre-frontal cortex leads to a lack of control over the limbic system, meaning people show sudden aggressive responses to perceived threats in the environment.
Overactivity in the amygdala has the same effect, if activated, people show high levels of aggression
How does serotonin influence aggression? (neural)
It is a neurotransmitter associated with communication of impulses between neurons and has an inhibitory effect on the brain. Low levels have been liked to poor self-control and impulsive behaviours including aggression
What does Virkkunen et al say about serotonin and aggression? (neural)
Aggressive behaviours are split into impulsive (hot-tempered/sudden) or non impulsive (cold, calculated). Low serotonin explains why people ‘flip’ and lose control over their aggression.
Evidence comparing the cerebrospinal fluid of violent-impulsive and violent non-impulsive offenders who significantly lower levels of serotonin metabolite in the violent-impulsive group, suggesting that their nervous system was in an excited state (fight or flight)
How do hormones effect aggression? (hormonal)
Males or more aggressive than females leading to people looking into testosterone. Testosterone is responsible for the development of masculine features during puberty such as height, build, deep voice, body hair and thought to be linked to aggression.
Evidence suggests that the prevalence of aggressive behaviours tend to correlate with fluctuating testosterone levels and males show more aggressive behaviours than females. When testosterone is reduced through castration, then number of aggressive behaviours also lower.
What are the strengths for neural explanations for aggression?
- Supporting evidence of role of amygdala: key in how we assess and respond to environmental threats. Gospic et al carried out fMRI in ps in lab-based game that provoked aggression. Scans showed aggressive reactions were associated with a fast and heightened response by the amygdala. Benzodiazepine taken before the game halved the number of aggressive reactions and decreased amygdala activity.
- Supporting evidence showing drugs that increase serotonin activity reduce aggressive behaviour: Berman et al split ps into two conditions where ps were given either a placebo or a dose of paroxetine. Ps then took part in a lab based game where they gave and received electric shocks in response to provocation. The placebo group gave more intense shocks than the group given paroxetine because the paroxetine group had experienced an increase in their serotonin levels. This was only true of ps who had a prior history of aggressive behaviour showing link between serotonin and aggression. LOW SEROTONIN CAN LEAD TO AGGRESSION, INCREASING CAN LOWER AGGRESSION
- Supporting evidence from case studies: Phineas Gage - damage to the limbic structures in his brain supporting the idea of the limbic system controlling aggression. Phineas Gage’s personality changed and he became more aggressive
What are the positive evaluation points for hormonal mechanisms of aggression?
- Supporting evidence from animal studies: Giammanco et al showed experimental increases in testosterone are related to aggression. Castration studies leading to a decrease in tesoterone and therefore a reduction in aggressive behaviour. This is a strength because it shows a direct link between testosterone and aggression in animals
- Evidence from Dabbs et al: They measured testosterone in the saliva of criminals and found those with the highest levels had a history of primarily violent crimes, whereas those with the lowest levels had committed only non-violent crimes. This suggests that testosterone levels may have caused this difference in aggression
What are the negative evaluation points for hormonal mechanisms of aggression?
Deterministic as findings are correlational may be due to a combination of factors not just low serotonin or damage to the limbic system
What are the genetic factors in aggression? (genes)
Twin studies, Adoption studies and MAOA genes
How do twin studies show genetic influences in aggression?
Twin studies have compared the aggression levels of MZ and DZ twins. The higher the concordance rate for aggressive behaviour between the twins, the higher the likelihood that their behaviour was biologically determined. Coccaro et al found in male ps with a history of physical assault, there was 50% concordance for MZ twins and 19% for DZ corresponding with their genetic profile. However cannot be purely genetic because otherwise would be 100%, Mz twins are also treated as more alike
How do adoption studies show genetic influences in aggression?
Rutter et al: compared the aggressive behaviour of adoptees to that of their biological parents (nature) and adoptive parents (nurture). Research suggests that criminality and aggression does have some inherited factors, as the participants’ aggressive history was more similar to their estranged biological parents. Inherited factors could explain around 41% variance compared to adoptive parents
How does the MAOA gene show genetic influences in aggression?
MAOA is an enzyme which breaks down neurotransmitters such as serotonin, dopamine and noradrenaline. Some develop an under active MAOA gene (Warrior gene) which only produce low levels of the MAOA enzyme which means there are higher levels of the neurotransmitters in these people’s brains. MAOA-L (low variant) has been associated with high levels of aggressive behaviour, hence showing inherited behaviour of a ‘warrior’
What are the positive evaluation points of genetic factors that influence aggression?
- Supporting evidence from animals: Godar et al used genetic depletion techniques to ‘knockout’ the MAOA activity in mice. When the mice had the MAOA gene ‘knockout’, they showed increased serotonin levels in the brain and hyper aggression. When the mice were given an SSRI they reverted back to their non-aggressive behaviours. This highlights the link between MAOA and serotonin activity
However findings may only be applicable to explaining aggression in animals rather than humans - Brunner et al studied 28 members of a Dutch family who all had a history of impulsively violent and aggressive behaviours, Findings showed that all these men had the ‘warrior gene’ (MAOA-L) which had led to low levels of the MAOA variant in their brains and thus high levels of serotonin and noradrenaline. This is good because it could help to identify individuals at risk of becoming violent
What are the negative evaluation points of genetic factors that influence aggression?
- Some research has identified low MAOA is linked to aggression but only in individuals who have experienced early trauma. Frazzetto et al (2007) found an association between antisocial aggression and Low MAOA gene variant in adult males but only in those who experienced significant trauma (e.g. sexual or physical abuse) during the first 15 year of life. Those who had not experienced trauma were not especially aggressive as adults even if they possessed the low-activity gene variant. Suggesting that a genetic explanation alone cannot fully account for aggression and therefore a diathesis stress explanation may be more appropriate. Furthermore, twin studies e.g. Coccaro et al (1997) found concordance rates for direct physical aggression in MZ twins is 50% and DZ twins is 19%. This shows that genes alone cannot fully explain aggressive behaviour.
- An issue of the genetic explanation is that twin studies may lack validity. Twins will share the same environment as each other however MZ twins tend to treated more similarly than DZ twins, especially by parents. This means the concordance rates may be inflated and the genetic influences on aggression may not be as high as the twin studies suggest.
What are the ethological explanations of aggression?
- Adaptive functions of aggression
- Ritualistic aggression
- Innate releasing mechanisms and Fixed action patterns
What are adaptive functions of aggression? (ethological)
An adaptive response which is beneficial for survival is when two members of the same species fight, they rarely kill their opponent but instead defeat them, and the victor gains territory, resources and mates.
Aggression serves a purpose of establishing social hierarchies within a group of animals. The most dominant male will exert power over the others in the social group, gaining special status such as being given the first opportunity to feed after a hunt, or having mating rights over the females. This can be seen in many animal species, including chimpanzees and lions.
What is ritualistic aggression? (ethological)
Carrying out certain behaviours in a specific set order. For example through certain ritualistic displays of aggression which occur before a physical fight. These techniques are used to scare off the opponent before it reaches the point of physical aggression; e.g. bearing teeth or claws, growling, roaring, and showing threatening body posture.
Lorenz identified ritualistic behaviours of a defeated animal, for example, cowering or whimpering. Chimps who lose a fight offer a subordinate hand display and lower their head to the victor. Wolves who are defeated expose their neck to show that the victor could rip out their throat with one bite and kill them if they wished. It is very rare that the victor would actually kill their opponent as this would affect their own genetic blood line, therefore these rituals work to clearly display the winner of the fight.
What are innate releasing mechanisms and fixed action patterns? (ethological)
Built-in physiological processes or structures, for example particular circuits in the brain, which are triggered by environmental stimuli. Once triggered, IRMs activate a certain sequence of behaviours which an animal is compelled to carry out; Fixed Action Patterns. Lea identified the main features of FAPs
What are the main features of FAPs? (ethological)
B - Ballistic: an inevitable course which much be completed
R - Response: to a specific stimulus that is viewed as a physical threat
U - Universal: to the specials
S - Stereotypical: unchanging sequences of behaviour
H - Hasn’t: been learnt
What are the positive evaluation points for ethological explanations for aggression?
Supporting evidence showing the role of IRMs and FAPs. Tinbergen found when male sticklebacks were presented with a seis of models, the sticklebacks would attack it in the same way, regardless of the shape of the model. If it had a red spot but would not attack it if no red spot was present, even if the model looked like a realistic stickleback. Supports the idea that members of the same species have an IRM that is triggered by a sign stimulus and supports features of FAPs. The FAPs were unchanging from one encounter to another and the attack always ran its course to completion
What are the negative evaluation points for ethological explanations for aggression?
- Idea that behaviour patterns are fixed has been criticised. Hunt argued that Lorenz underestimated the role of the environment in developing these behaviour patterns and that learning and experience interacts with innate factors to produce subtle variations in behaviour. Members of the same species have been shown to differ in the duration of each behaviour, and even the same animal from one encounter to another. This is a problem that led to ethologists to move away from the term FAPs replacing it with Behaviour Pattern to reflect that these behaviours can be modified by experience
- Evidence against ideal of ritualistic aggression. Goodall observed chimpanzees at a national park in Tanzania. The aggression of two rival communities of male chimps was not impulsive but coordinated and planned like a military operation to te point that she dubbed it the ‘four-year war’. One group of males systematically slaughtered the other community in a gang fashion, holding down individual chimps and carrying out prolonged attacks. They ignored the victim’s signals of defencelessness and defeat, hitting and biting them until they were dead. This is a weakness because it questions the idea that animal aggression is often ritualistic rather than real
- Findings cannot be generalised to human aggression. Animals are qualitatively different to humans in their aggression. Tinbergen studied fish, Lorenz studied birds and mammals. Both researchers extrapolated their findings to try to explain human aggression. Humans are more complex than animals and show a range of different aggressive behaviours; active or passive, impulsive or calculated. It would be invalid to compare human aggression directly to animal. Therefore these findings may not be able to explain the complex and less predictable ways humans show aggression
What are the evolutionary explanations of human aggression?
Sexual competition and sexual jealousy
How does sexual competition lead to human aggression? (evolutionary)
Ancestral males seeking access to females would have had to compete with other males. One way of eliminating this competition would have been through aggression. The successful individual would have increased their social status and been ore successful in acquiring and protecting their mates from competing males and so would be more successful in passing on their genes to the offspring. This would then have led to the development of a genetically transmitted tendency for males to be more aggressive to other males
What do evolutionary psychologists argue about aggression?
That it is adaptive as it would have been effective for solving a number of survival and reproductive issues among early humans. Acquiring and defending resources, intimidating or eliminating male rivals for females, and deterring mates from sexual infidelity. Solving these problems enhance the survival and reproductive success of the individual and therefore these behaviours would have spread through the gene pool, becoming common amongst all humans
How does sexual jealousy lead to human aggression? (evolutionary)
Aggression arises as a result of paternal uncertainty. Unlike women, men can never be entirely certain that they are the fathers of their children. Therefore men are always at risk of ‘cuckoldry’. Wilson and Daly identified several mate retention strategies used by males
What are the mate retention strategies used by males? (evolutionary)
Direct guarding - vigilance over their partner, keeping tabs on them to ensure they are not seeing other men
Negative inducements - threatening their partners if they act in a way which he doesn’t want them to