Aggression

Neural mechanisms-Limbic system

Gyrus,septal area,hypothalamus,fornix,amygdala+parts hippocampus+thalamus.most important-amygdala-reactivity of it proven be important predictor of aggressive behaviour.

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Neural Mechanisms-limbic system-Gospic 2011

Ultimatum game-assess aggressive beha+found when responders rejected unfair offers-scans revealed fast+heightened repsonse by amygdala+found benzodiazapine drug taken before game had 2 effectson on responses unfair offers-halved number rejections

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What else did it do?

decreased activity amygdala-strong evidence of association between reactive aggression+amygdala activity

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Neural Mechanisms in aggression-Serotonin

Neurotransmitter involved communication of impulses between neurons.It slows down+dampens neuronal activity.normal levels serotoning in orbifrontal cortex r linked with reduced firing of neurons+this is associated w greater degree of self control

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What can decreased serotonin do?

may disturb this mechanism,reducing self control+leading to an increase in impulsive behaviour including aggression-Denson et al.

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Serotonin-Virkkunen et al - supporting role of serotoning in reactive aggression

compared levels serotonin break down product in the cerebrospinal fluid of violent impulsive offenders+they also suffered sleep irregulalities-significant cus serotoning regulates sleep patern-implies disturbance serotoning functioning

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Neural Mechanisms-evaluation-role of other brain structures

recent studies indicate that amygdala doesnt operate in isolation n determing aggression-appears function w orbitofrontal cortex which isnt part limbic system-indictates regulation of aggression highly complex+involves at least 3 neural structures

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Neural Mechanisms-evaluation-effects of drugs on serotonin

Drugs that increase levels serotonin also reduce levels aggressive behav.Berman-gave P placebo or dose paroxetin-then took part in lab game-the drug p gave fewer+less intense shocks-only true for p w history aggresive behav-

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What does that show

Link between serotonin function+aggression that goes far beyond usual correlational findings

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Hormonal mechanisms in aggression-Testostorone

Giammanco et al demonstrated experimental increases in testostorone r related to greater aggressive behaviour in several species+Dolan et al found P+correlation testo levels+aggress beh in 60 male offenders in uk maximum security hospital+historyviol

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Hormonal Mechanisms in aggression-evaluation-explaining the role of Testostorone

Mazur-biosocial model of status-explain link tostestorone+aggression-tost levels change during day+following loss status-should affect post-competition aggression eg-has affect on aggression

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Hormonal Mechanisms in aggression-evaluation-other hormones

Carre+Mehta-dual hormone hypothesis-claim high levs testo lead aggress beh only when levels of cortisol r low.-when cortisol high-testo influence on aggress blocke-combined activity may better predictor of aggress than hormonal alone

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Genetic factors in aggression-Twin Studies

suggest genetic factors account 50% variance in aggress behav.Coccaro MZ+DZ twins-MZ share 100% genes+DZ 50%-would find greater similaeity agg in MZ if influenced mostly genetic.phsicial assoult concordance rate MZ 50%+DZ 19%

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What is the concordance rate for verbal aggression?

MZ 28%+ DZ 7%

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Genetic factors in aggression-Adoption studies

Rhee+Waldman Meta analysis of adoption studies od direct aggress+antisocial behav.found genetic influences account 41% of variance in aggression.

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Genetic factors in aggression- MAOA gene-enzyme

role is to mop up neurotrasnmitters in brain after nerve impulse has been transmitted from 1 neuron to another-by breaking down neurotransmitter-espsecially serotoning into constituent chemicals to be recyle-production of this enzyme is MAOA gene

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What happens if theres a dysfunction in the operation of this gene

may lead abnormal activity of the MAOA enzyme which affects levels serotoning in brain.

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What is 1 variant of the MAOA gene

Warrior gene-leads low MAOA activity in brain+has been associated w various forms aggress beha-eg Han Brunner et al studied 28male of dutch fam who repeatedly involved aggress violent crime behav-found that these men had abnormal low levels MAOA

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Genetic factors in aggression-Gene-environment intercations

Genes crucial influence but dont function in isolation.Appears low MAOA gene only related to adult aggression when combined with early traumatic life events -Frazetto found association high levels antisocial aggres+low maoa-but only case those trauma

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During the first 15 years of life

.

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Genetic factors in aggression-evaluation-Isolating Genetic Factors

Researchers have difficulty separating genetic+environmental factors-Mcdermott et al showed that P with low activity maoa behaved aggressively in lab based money allocation but only when provoked-otherwise no more or less aggressive than other p

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Genetic factors in aggression-evaluation-Multiple genetic influences

Stuart et al-intimite partner violence associated not just low activity maoa but also w serotonin transpoter gene-influences serotonin activity+Vassos couldnt find evidence association between any single gene+aggression

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Genetic factors in aggression-evaluation-Measuring aggression

methods of measuring aggression differ significantly between studies+include self reports-Rhee+Waldman meta analysis of 51twins+adoption studies-genetic factors had great influence on aggress in studies using self report rather than parent or teacher

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What does that mean?

If reasearch findings vary depending upon how aggression measured-becomes difficult draw valid conclusion about role of genetic factors

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The ethological explanation of aggression-Adaptive functions of aggression

aggression beneficial to survivial cus 'defeated' animal rarely killed but forced establish somewhere els-means species spread out wider area+discover resources in diff places-reduces competition pressure+possibility starvation.

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What is another adaptive function?

Establish dominance hierarchies-Pettit et al-studied play groups of young human children+observed how aggression played role in development of some childrens dominance over others-would be adaptive cus dominance over others brings benefits-get ownway

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Ethological explanation of aggression-Ritualistic aggression-series behaviours carried out in set order

Lorenz observation-most aggress encounters were ritualistic signalling-eg display claws,facial expressions threat+rarely became physical.+pointed out inta species aggress confrontations end with ritual appeasment display-acceptance defeat

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Ethological explanations of aggression-Innate releasing mechanisms+fixed action patterns

IRM is built in physiological process-network neurons in brain .An enivornmental stimulus triggers IRM which then releases -FIXED ACTION PATTERN

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According Stephen Lea -FIXED ACTION PATTERN have 6 main features-what are thefirst 4

Steotyped ur unchanging sequence of behaviours,Universal-cus some behav found every individual,Unaffected by learning-same for every indivudual regardless experience,Ballistic-once behav triggered follows inevitable course+cant alter before completed

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Fixed action pattern-What are the last 2?

Single purpose,behaviour only occurs in specific situation+not any other,A Response to An Identifiable Specific Sign Stimulus-or if it involves ommunication between members of same species, known as releaser

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Aggression

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