Aggression Flashcards
What is proactive aggression?
Planned method of getting what is wanted
What is reactive aggression?
Angry and impulsive, accompanied by psychological arousal
What are the 2 neural mechanisms to explain aggression?
The limbic system
Orbitofrontal cortex + seretonin
What is the limbic system?
Subcortical structures in the brain (including amygdala + hippocampus) involved in regulating emotional behaviour, such as aggression
How is the amygdala involved in aggression? What is the name of the study to provide evidence for this?
Quickly evaluates environmental threats’ importance to provide an appropriate response
The reactivity of the amygdala is an important predictor of aggressive behaviour
Gospic et al
How does Gospic et al’s study illustrate the role of amygdala activity in aggression?
Ultimation game where unfair offers led to provocation
fMRI scan showed fast + heightened response by amygdala
If benzodiazepine given before provocation, decreased activity of amygdala + halved the number of aggressive reactions
How is the hippocampus involved in aggression? What is the name of the study to provide evidence for this?
Associated with LTM, can compare conditions of current threat with similar past experience
If impaired, prevents nervous system from placing in relevant context, leading to inappropriate amygdala reaction
Boccardi et al
How does Boccardi et al’s study illustrate the role of hippocampus activity in aggression?
Habitually violent offenders exhibited abnormal hippocampus functioning
How does serotonin in the orbitofrontal cortex affect aggression?
At normal levels in the OFC, the neurotransmitter has a calming effect and inhibits amygdala firing
What is the serotonin deficiency hypothesis?
Low serotonin levels means the amygdala is more active, resulting in impulsion and aggression
What is the study to support the role of serotonin in aggression?
Virkkunen et al
Levels of a serotonin breakdown product is significantly lower in violent IMPULSIVE offenders than violent NON-IMPULSIVE offenders
What is a strength and weakness of neural mechanisms explaining aggression?
Research into the effects of drugs- paroxetine increases serotonin and decreases aggression
- Berman et al either paroxetine or placebo group
- Paroxetine group gave fewer + less intense electric shocks in a lab game
Causal link between seretonin and aggression
Non-limbic brain structures also involved in aggression
-limbic system functions with OFC
- OFC involved in impulse regulation + inhibition of aggression
- Cocarro et al, OFC activity reduced in disorders causing aggression as disrupts impulse control
Neural regulation of aggression is more complex than just the amygdala
What are the 2 hormonal mechanisms to explain aggression?
Testosterone
Progesterone
How does testosterone influence aggression?
It is a male sex hormone (androgen) responsible for the development of male characteristics, such as aggression
Men reach peak aggression around 20 years, when testosterone levels are highest
Its action on brain areas is implicated in aggression
What is the research that supports testosterone influencing aggression?
Giammanco et al
Castration animal studies- removed the testes (source of testosterone)
This reduced aggression in males of many species
Injecting synthetic testosterone restores aggressive behaviour
How may the female ovarian hormone ‘progesterone’ play a role in aggression in women?
Levels of progesterone vary during menstrual cycle, lowest just after menstruation
Negative correlation between progesterone level and self-reported aggression
Thus, low levels are linked to aggression in women
Who devised the duel-hormone hypothesis?
Carrè and Mehta
What is the duel hormone hypothesis?
Cortisol plays central role in stress response
Low cortisol allows high testosterone levels to lead to aggression
But high cortisol means that testosterone’s influence on aggression is blocked
What is a strength and weakness of hormonal mechanisms explaining aggression?
Research support from non-human studies
- Giammanco et al castration
- he also reviewed studies and found: 1. during monkey mating season, increase in testosterone and aggression 2. injecting female rats with testosterone increases mousekilling
Demonstrates role of testosterone in a range of species
Mixed evidence on link between testosterone and aggression
- duel hormone hypothesis
- testosterone only leads to aggression when cortisol levels low
Combined activity a better predictor of aggression than testosterone alone
How are genetic factors influencing aggression studied?
Twin studies
Adpoption studies
How can twin studies explain how genetic factors influence aggression? Give the findings from one study
If monozygotic twins are more alike in terms of aggression, than due to genes
Coccaro et al: genetic factors account for 50% variance in direct aggressive behaviour (19% dizygotic)
How can adoption studies explain how genetic factors influence aggression? Give the findings from two studies
If positive correlation between aggression in adopted children + biological parents, there is a genetic effect
Hutchings et al: significant number of adopted boys with criminal convictions had biological dad with violent convictions
Rhee + Waldman: meta-analysis of adoption studies, genetic factors accounted 41% variance in aggression
What gene is linked to aggression?
MAOA
What does the MAOA gene do?
Controls production of monoamine oxidase A (MAO-A) enzyme
This regulates serotonin which plays a role in aggression
Which variant of the MAOA gene is linked to aggression?
MAOA-L (low activity/deficiency of MAO-A)
Thus, abnormal serotonin levels, increased aggression
What study looks at the MAOA gene influencing aggression?
Brunner et al
Studied impulsive, aggressive Dutch criminal family
All had low levels of MAO-A enzyme, and MAOA-L variant
What are gene-environment interactions also known as?
Diathesis stress
Epigenetic effect
What do gene-environment interactions suggest? Include research
Environment (eg: early trauma) influences affect the expression of genes
Frazzetto et al: association between aggression and MAOA-L, but only if experienced trauma in first 15 years of life
What is a strength for genetic factors in aggression?
Support for role of MAOA gene in aggression
- Mertins et al
- MAOA-H were more cooperative + less aggressive in lab task
- converse is true
SUpports importance of MAOA gene in aggression
What are 3 weaknesses of genetic factors in aggression?
Mertins’ study showed non-genetic factors are crucial
- MAOA-L participants behaved cooperatively when aware others were
- knowledge of social norm determined aggression
Genes influenced by environmental factors
Twin studies may lack validity
- assume DZ treated same as MZ (equal environments assumption)
- but DZ treated less similarly, inflating concordance rate
Genetic influence on aggression not so big
Findings depend of how aggression is measured
- measures differ eg: self-report, observation
- Rhee and Waldman found greater genetic influence on aggression in self-report studies than parent/teacher report
- findings differ depending on measurement
Hard to draw valid conclusions on the role of genetic factors
What is ethology?
Study of animal behaviour in natural settings
How is aggression described according to the ethological explanation?
Adaptive + ritualistic
How is aggression adaptive (beneficial to survival)?
- defeated animal rarely killed, finds new territory so spreads out for resources, decreases competition and possible starvation
- establishes dominance hierarchy, provides access to mates/food
Pettit et al found aggression played important role in dominance hierarchies for young children
Why is aggression ritualistic?
Lorenz found that fights of the same species resulted in little physical damage
How is aggression ritualistic?
Ritualistic signalling (eg: display teeth) to assess relative threat
Loser displays submissive appeasement gesture to prevent harm (eg: wolf exposes neck)
This is all adaptive as it doesn’t threat the existence of the species
What is an innate releasing mechanism?
Inbuilt physiological process activated by an environmental stimulus to trigger FAP
What is a fixed action pattern?
Specific sequence of pre-programmed behaviour triggered by an IRM
How does a sign stimulus trigger an FAP?
Sign stimulus → sensory recognition → IRM → motor control activates FAP
Who devised the 6 main features of FAPs? What are they?
Lea 1984
Stereotyped
Universal
Unaffected by learning
Ballistic
Single-purpose
Response to an identifiable specific sign stimulus
Who researched into male stickleback fish?
Tinbergen
What did Tinbergen find in his research?
Male sticklebacks are highly territorial during mating season and develop a red spot on underbelly
The red spot is a sign stimulus, triggering an IRM, triggering an aggressive FAP
If a model had red spot, fish would aggressively display = attack, regardless of shape
If no red spot, no FAP, even if realistic
What is a strength of the ethological explanation of aggression?
Research support related to genetics
- Brunner et al showed MAOA-L gene closely associated with aggression
- twin/adpotion studies show significant genetic component to aggression in humans
- shows innate basis to aggression
Ethological explanation is valid in claiming aggression is genetically determined/heritable
What are 3 weaknesses of the ethological explanation of aggression?
Cultural differences in aggressive behaviour
- Nisbett found some homicide more common in white men in south USA than Northern states
- due to ‘culture of honour’ in south
- aggression is from social norm, not instinctive
Culture overrides innate predispositions, ethological theory fails to explain this
FAPs not that fixed
- Hunt found they are greatly influenced by environment + learning
- now prefer ‘modal behavioural pattern’
Much more flexible than thought
Unjustified generalisations to human aggression
- Lorenz didn’t study higher mammals
- Tinbergen didn’t study extremely destructive violence
- Lorenze extrapolated animal behaviour to countries
Should be more cautious as humans have more complex behaviours eg: warfare