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AGGRESSION, NEURAL - Coggle Diagram
AGGRESSION
GENETIC FACTORS IN AGGRESSION
twin studies
because mz twins share 100% of their genes but DZ share on.y 50%, we would expect to find greater similarities in aggressive behaviour between MZ twins if aggression is mostly influenced by genetic factors. MZ and DZ share same environment but mz have greater genetic similarity. researchers found concordance rates of 50% for MZ twins and 19% for DZ.
adoption studies
meta analysis of adoption studies pf direct aggression and antisocial behaviour. genetic influences accounted for 41% of the variance in aggression, more or less in line with findings from twin studies.
the MAOA gene.
an enzyme that mops ip neurotrasnmitters after a nerve iimpulse from one neutron to another. the production of the MAOA enzyme is determined by the MAOA garner. a dysfunction in the operation of this gene can lead to abnormal activity of the enzyme, in turn disrupting levels of serotonin. one variation (warrior gene) leads to low MAOA activity and has been associated with various forms of aggressive behaviour.
28 male members of a large dutch family repeatedly involved in violent crimes such as rape, attempted murder snd assault. found that these men that had abnormally low levels of MAOA in their brains and low activity version of the MAOA gene.
gene-environment interactions (GxE)
genes crucial influences on aggressive behaviour but do not function in isolation
low MAOA gene activity is only related to adults aggression when combined with early traumatic life events
NEURAL AND HORMONAL MECHANISMS OF AGGRESSION
the limbic system
AMYGDALA has important role I humans and nonhuman and how they respond to environmental threats and challenges. reactivity of amygdala an important predictor of aggressive behaviour.
Ultimatum game- proposer offers to split money certain way. if responder accepts, money is split as proposed, if rejects, both receive nothing,
found that when received an unfair offer, the scans revealed a fast and heightened response of amygdala. when drug that reduces arousal of nervous system used, they found that it halved the number of rejections and decreased activity in amygdala
serotonin
widespread inhibitory affects on the brain. slows down and dampens neuronal activity, normal levels of serotonin linked with reduced firing of neutrons this is associated with greater degree of self control. Decreased serotonin may disturb this mechanism, reducing self control and ,eating to an increase in impulsive behaviour.
compared levels of serotonin in violent impulsive and violent non impulsive offenders, found that there significantly lower serotonin in impulsive offenders and also had more sleep irregularities. this is significant as serotonin regulates sleep patterns.
EVALUATION
drugs that increase serotonin, decrease levels of aggressive behaviour. participants given either a placebo or a dose of paroxetine, a drug that enhances serotonin activity. laboratory based game where shocks of varying intensity were given. found that the drug group gave fewer and less intense shocks than those in placebo group. only true of the participants who had a prior history of aggressive behaviour.
hormonal mechanisms of aggression
testosterone- regulates social behaviour. Animal studies demonstrated experimental increases in testosterone re related to greater aggressive haeviouor in several species.
some evidence for a similar association comes from studies of prison populations, positive correlation between testosterone levels and aggressive behaviours in a sample of 60 male offenders in maximum security hospital.
EVALUATION
research to support- measures changes in male participant testosterone levels before and after a competitive game which they all lost. after second sample they could wither rechalleneg (AGRESSIVE) or unrelated task (NON AGRESSIVE) of the losers who's testosterone rose, 73% rechallenged, but of losers whose testosterone dropped, 22% rechallenged. this research supports the idea that there is a plausible explanation of how testosterone may exert its effects on aggression.
Media influences on aggression
effects of computer games on aggression
experimental studies
students played either a violent computer game or a nonviolent game for 10 minutes, they then all carrie out a reaction Tim test, in which they blast levels of white nose to punish non existent opponent. this who played the vilent game selected significantly higher noise levels compared with non violent players. (5.97 compared to 4.60)
evalutation- allow us to establish a casual link between media aggression and aggressive behaviour. weakness of these studies is that its accused of being artificial and unrealistic. They do not involve any fear of retaliation- unlike in the real world, the participant can be safely aggressive without fear of being hurt back.
correlational studies
227 juvenile offenders- aggressive behaviours- using structured interviews they found that the offenders aggressive behaviours was significantly correlated with how often they played violent computer games and how much they enjoyed them. link so well established it should be considered a public health issue
evaluation- direction of causality cannot be settled by correlational studies. Soicalisation hypothesis- states that aggrieve media causes people to become more aggressive. Selection hypothesis, claims that people who are already aggrieve select aggressive media.
longitudinal studies
1037 people measured their TV viewing hours. found the time spent watching Tv was a reliable prediction of aggressive behaviour. those who watched the most tv also were more likely to be diagnosed with antisocial personality disorder.
evaluation- studying change over time leaves longitudinal sties vulnerable to the effects of confounding variables. many other sources of aggression interact with media influences over a period of time, such as role models in the form of friends and family members.
meta- analyses- performed a meta analysis of 136 studies. exposure to violent computer games was associated with increases in aggressive behaviour. true for both male and females across colectivist and individualistic cultures.
NEURAL