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Biological Explanations of aggression
Outline the Genetic explanation of Aggressive behaviour.20 marks
A01Aggression is HereditaryGenetic Mutations (XYY)Inter-breeding in Animal Studies with aggressive phenotypesResearched with twin studies (Mz vs. Dz to discover concordance rates)Researched in Adoption Studies with violent histories in biological parents but not adoptive parents
A02Twin studies concordance rating(Mason & Frick) 48% genetic Adoption studies(Hutchings & Mednick) Denmark 14000 adoptions, significant positive correlation only between bio. Parents and child.Case Studies (Brunner) MAOA & (Sandbarg) XYY Animal Studies(Lagerspetz) Aggressive mice interbred, 19th generation more aggressive
AO3
GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism
4
Biological Explanations of aggressionNeural anatomyNeural chemistryPlan 24 mark on Neural explanations of aggression
Can anyone explain what these are? (class discussion hands up activity) Then go through and explain each. Then get them to link these to aggression, very basically e.g. Might be a gene that causes aggression, does anyone know any hormones that might explain it?6
Neurotransmitterschemicals which allow the transmission of signals from one neuron to the next across synapses
Neurotransmitters what we already knowDecreased levels of Serotonin Enzymes = Increased Aggression
Warrior Gene
HoweverHigher levels of serotonin may not be the whole story
NeurotransmittersSerotonin has a relaxation function
It inhibits aggressive behaviour
Neurotransmitters what we already knowDecreased levels of Serotonin Enzymes = Increased Aggression
Warrior Gene
Low levels of SerotoninAggressionImpulsive BehaviourViolent SuicideDepressionAlcohol AbuseOver eating
Low levels of Serotonin can lead to an increase in aggression
Serotonin inhibits our response to emotional stimuli that can lead to aggressive behaviour
Reduced Serotonin = Reduced ability to control aggressive impulses
Low levels of SerotoninAlcohol and Aggression
Increased alcohol consumption is often positively correlated with aggression
Alcohol causes a decrease in Serotonin levels
The reduction in Serotonin stops inhibition of aggressive behaviour
Low levels of serotoninHigley (1996)
Free-ranging, male, rhesus monkeys
Higley (1996) Monkeys Serotonin levels were measured
Those with the lowest Serotonin were more likely toFightHave more scars and woundsPick fights with larger opponentsJump from trees higher than 7 metres
Serotonin & Drug therapy Drugs that decrease levels of Serotonin can be used for weight control
Drugs that increase levels of Serotonin can be used to treat depression (Prozac)
Mann et al (1990)
Drug Dexfenfluramine reduces appetite by reducing Serotonin
The drug was given to 35 healthy participants
Questionnaire was given to all pps to assess hostility before & after treatment
Mann et al (1990)
Results showed that male pps were more hostile after taking the drug
This result was not found in females.
Serotonin & Drug therapy Bond (2005)
Prozac is an anti-depressant which increases Serotonin
Individuals who take Prozac experience reduced impulsive aggressive behaviour
Mann et al (1996)Violent suicide associated with lower levels of Serotonin
Low serotonin & criminal behaviourDavidson et al (2000)
Criminals with more violent history of criminality had markedly lower levels of Serotonin compared with non-violent criminals.
NeurotransmittersAggression is linked to
Low levels of Serotonin High levels of Dopamine
DopamineDopamine and Aggression link is much less well established than Serotonin
There is some evidence of a link between high levels of Dopamine and an increase in Aggressive Behaviour
DopamineProduced in response to rewarding stimuli
Food SexRecreational Drugs
Couppis et al (2008)
Dopamine plays reinforcing role in aggression
Some individuals seek out aggressive encounters because of the rewarding sensations they provide caused by an increase in Dopamine
Dopamine & Drug TreatmentAmphetamines increase Dopamine levels
Research has found an increase in Aggressive behaviour by individuals under the influence of Amphetamines(Lavine, 1997)
Dopamine & Drug TreatmentAnti-psychotics reduce Dopamine
When violent delinquents are given these anti-psychotics, aggression is reduced. (Buitelaar, 2003)
Conclusion of Neurochemistry & AggressionEvidence for the dual role of Serotonin and Dopamine has been found in Animal Studies
Ferrari et al (2003)Allowed rats to fight every day for 10 days
On the 11th day, it was not allowed to fight and its serotonin and dopamine levels were measured
In anticipation of a fight, the rats Dopamine levels had increased and Serotonin levels had decreased
AO3
GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism
32
Can anyone explain what these are? (class discussion hands up activity) Then go through and explain each. Then get them to link these to aggression, very basically e.g. Might be a gene that causes aggression, does anyone know any hormones that might explain it?33
Neural Anatomy (Brain Structure) & AggressionAre aggressive brains structurally different to non-aggressive brains?
Pre-Frontal CortexHypothalamusAmygdala
Hypothalamus Controls hormone release
Regulates:TemperatureThirst/HungerSleepMoodSex Drive
Hypothalamus Siegel & Pott (1988)Research with cats
Activation of the hypothalamus causes aggressive response and vicious attack behaviour
AmygdalaEmotion centre
Emotional ResponseAutonomic resoponse to fearMemory
Amygdala & AggressionPotegal (1996)Direct Stimulation of Amygdala causes Aggressive behaviour in Hamsters
The Amygdala remains active half an hour after violent attackRed Alert
Amygdala & AggressionPotegal (1996)
Also found heightened Amygdala activity 5-20 mins after aggressive provocation in humans
Pre-Frontal Cortex (PFC) Higher level CognitionDecision Making
Pre Frontal Cortex & AggressionCase of Phineas Gage
Personality became more impulsive and aggressive following injury to PFC
Pre Frontal Cortex & AggressionRaine et al (1997)
PET scans of 41 murders compared to matched controls
Murderers had significantly lower levels of activation in the PFC
Outline Neural Explanations of Aggression(20 marks)A01 Outline NT effects (Sr & Dp) & outline neural structures (Hp, Am & PFC)
A02 Evaluate with studies Animal Studies, Drug therapy, Case studies
A03 Reductionist; Nature not Nurture; Animal Studies; Deterministic