AGGRESSION Flashcards
What is the limbic system?
- A system of structures lying beneath the cortex (i.e. subcortical)
^— includes AMYGDALA, HIPPOCAMPUS, HYPOTHALAMUS - Though to be closely involved in regulating emotional behaviour (e.g. aggression)
Explain the role of the amygdala in aggression
- Responsible for quickly evaluating emotional importance if sensory information, prompting an appropriate response
- INCREASED REACTIVITY = INCREASED LIKELIHOOD OF AGGRESSION
- If certain areas are electrically stimulated, individual is aggressive
^— area is surgically removed = decreased aggression
Outline support for the role of the amygdala in aggression
- Kluver + Bucy (1937)
- Discovered destruction of the amygdala in a monkey who was dominant in a social group caused it to lose its dominant place in the group
Explain the role of the hippocampus in aggression
- Involved with formation of LTM + allows animal to compare conditions of a current threat w/ similar past experiences
^— e.g in animal had previously been attacked by another animal, the next time that animal is encountered they are likely to respond with aggression or fear - Impaired hippocampal function prevents nervous system from putting things into a relevant and meaningful context - causes amygdala to respond inappropriately to sensory stimuli (results in aggression)
Outline support for the role of the hippocampus in aggression
- Boccardi et al. (2010)
- Found habitually violent offenders exhibited abnormalities of hippocampal functioning
What is serotonin?
A neurotransmitter with widespread inhibitory effects throughout the brain
^— includes roles in aggression, eating behaviour, sleep + depression
Explain the role of serotonin in aggression
Normal levels of serotonin in the orbitofrontal cortex (OFC) = greater behavioural self-control
^— therefore, DECREASED serotonin = reduced self-control + INCREASED impulsive behaviours (e.g. aggression)
Outline support for the role of serotonin in aggression
- Virkkunen et al. (1994)
- Found DECREASED levels of serotonin in violent-impulsive offenders compared w/ violent non-impulsive offenders
What is testosterone?
- A hormone from the androgen group that is produced mainly in the male testes (and in smaller amounts in the female ovaries)
^— associated with aggressiveness
Explain the role of testosterone in aggression
- produces male characteristics (one of which thought to be aggressive behaviour)
- Levels reach peak in young males, then decline
- The male sex hormone testosterone is thought to to influence aggression from young adulthood onwards due to its action on brain areas involved in controlling aggression
Outline support for the role of testosterone in aggression
- Dolan et al. (2001)
- Found violent prisoners in maximum security prisons displayed INCREASED testosterone than non-violent (e.g. fraud)
- Giammanco et al. (2005)
- Removing the testes (castration) caused a decrease in aggression
- Injecting testosterone caused an increase in aggression
- Daly and Wilson (1998)
- At an age when testosterone concentration are at their highest (21-35), there is an increase in male-on-male aggressive behaviour
Describe the role of twins studies as a way of determining to the role of genetics in aggression
- MZ twins share all genes while DZ share 50%
^— in twin studies, researchers compare the degree of similarity for a particular trait (e.g. aggression) between sets of MZ twins + compared to this to the similarity between sets of DZ twins - If MZ twins are more alike in terms of aggressive behaviour, then it should be due to genes rather than environments (both types of twins share the same environment, but MZ twins are more genetically alike)
Outline support for twin studies as a way of determining to the role of genetics in aggression
- Coccaro et al. (1997)
- Studied adult male MZ + DZ twins
^— physical aggression had concordance rate of 50% for MZ + 19% for DZ
^— verbal aggression had concordance rate of 28% for MZ + 7% for DZ
Describe the role of adoption studies as a way of determining to the role of genetics in aggression
- Adoption studies can help untangle the relative contributions of environment + hereditary in aggression
- If a positive correlation is found between aggressive behaviour in adopted children + aggressive behaviour in bio parents, a genetic effect is implied
- Is a positive correlation is found between the adoptee’s aggressive behaviour + the rearing family, an environmental effect is implied
Outline support for adoption studies as a way of determining to the role of genetics in aggression
- Hutchings + Mednick (1975)
- Study of 14000 adoptions found SIGNIFICANT NO. of adopted boys with criminal convictions had bio parents with criminal violence convictions
What is the MAOA gene?
- Responsible for the activity of the enzyme monoamine oxidase in the brain
^— enzyme regulates the metabolism of serotonin in the brain - Low-activity variant of the gene is closely associated with aggressive behaviour
Explain the role of the MAOA gene in aggression
- Gene controls monoamine oxidase A (MAO-A) enzyme production
- DECREASED activity of MAOA gene may lead to DECREASED levels of MAOA enzyme
^— therefore INCREASED serotonin —> links to INCREASED aggression
Outline support for the role of the MAOA gene in aggression
- Brunner et al. (1993)
- Studies 20 MALE family members of a Dutch family repeatedly involved in impulsively violent criminal behaviours (e.g. rape, attempted murder, assault)
^— found to have abnormally low levels of MAOA enzyme in their brains + low activity in MAOA gene
MAOA-L
Outline support for the role of the MAOA-L + MAOA-H variants in aggression
- Caspi et al. (2002)
- Involved study on 500 male children’s
- Discovered variant of the gene associated with high levels of MAOA (MAOA-H) and another variant associated w/ low levels (MAOA-L)
- Those with MAOA-L were significantly more likely to grow up to exhibit anti-social behavior but ONLY if their had been maltreated as children
- Those with MAOA-H variant who were maltreated, and those with MAOA-L BUT NOT maltreated, did non display anti-social behaviour
What is ethology?
The study of animals
What are ethological explanations ?
Stress the adaptive value of animal behaviours
^— ethologists study behaviour patterns of animals in their natural environments
How is aggression adaptive?
- Defeated animal is forced to relocate to different territory, decreasing competition
- Establishes dominance hierarchies
Give support for the adaptive function of aggression
- Pettit et al. (1988)
- Observed aggression in human children
- Observed how aggression in play lead to dominance hierarchies
^— adaptive because dominance over others brings benefits such as power to get your own way or to access resources
What is ritualistic aggression?
- Aggressive behaviour that may be ritualised (carried out in a set order) in the form of threat displays
- Lorenz (1966) observed most aggression in species rarely leads to severe harm
- Results in appeasement displays - indicating acceptance of defeat + reduces aggression in the winner, preventing injury
What are appeasement displays?
- Backing down
- Displayed by losing individual submissively exposing neck to its adversary
^— may even display stomach or lower head - Instinctive inhibitions prevent the dominant animal from continuing the fight
- Lorenz (1952) - non-hunting species have no powerful natural weapons + have not developed same inhibitions against hurting own kind
What is a FAP?
- Fixed action pattern
- A sequence of stereotyped pre-programmed behaviours triggered by an innate releasing mechanism which do not require learning
What is an IRM?
- Innate Releasing Mechanism
- A biological structure or process (e.g. in the brain) which is activated by an external stimulus that in turn triggers a fixed action pattern
Explain the mechanism of an IRM and FAP
- IRM receives its input from sensory recognition circuits that are stimulated by the presence of the sign stimulus
- IRM then communicates with motor control circuits to activate the FAP associated with that sign stimulus
What are the characteristics of FAPs?
- Stereotyped (always occurs in the same way)
- Universal (behaviour is the same in all conspecifics)
- Independent of individual experience (behaviour is innate w/ no learning involved)
- Ballistic (once triggered, cannot be stopped
- Specific triggers (each FAP has a specific trigger/sign stimulus)
What are evolutionary explanations of aggression?
Focus on the adaptive nature of behaviour (i.e. modern behaviours are believed to have evolved because they solved challenges faces by our distant ancestors + so become more widespread in the gene pool)
Outline aggression in sexual competition
- Ancestral males seeking access to females would have had to compete with other males (intrasexual selection)
- One way of eliminating competition would have been through physical competition
- Individuals who used aggression successfully against competitiors would have been more successful in acquiring mates + would be more successful in passing on their genes to offspring
^— Would have lead to the development of a genetically transmitted tendency for males to be aggressive towards other males
Give support for aggression in sexual competition
- Puts (1988)
- Men have 75% more muscle mass than women
- Universally, males have thicker jawbones + stronger skulls than females
^— both factors allow for success in physical competition + accumulation of resources = adaptive for survival + reproduction so aggressive genes are passed on
Outline aggression in sexual jealousy
- Male aggression can occur due to sexual jealousy which arises as a result of paternal uncertainty
- Men are always at a risk of cuckoldry + might unwittingly invest resources into offspring not genetically his
^— the adaptive function of sexual jealousy would have been to deter a mate from sexual infidelity, minimising the risk of cuckoldry
Give support for aggression in sexual jealousy
- Buss (1988)
- Males have evolved mate retention strategies (mate guarding) which can include aggressive behaviour
- Mate guarding: restricting freedom to prevent males gaining access (e.g. stopping partner speaking w/ other men)
- Negative inducements. - issuing aggressive threats about potential consequences of infidelity (“I will kill you/myself/the children if you leave me”)
Outline aggression in warfare
- War is dangerous + costly, so difficult to see why an organism, selected to survive, should engage in behaviours associated with such extremes of personal costs + danger
- Evolution: leads us to expect that any behaviour associated with warfare would have evolved because of the adaptive benefits of the individual and their offpsring
Give research support for aggression in warfare
- Livingstone Smtih (2007)
- Claims human warfare originated not only to obtain valuable resources but also to attract mates + forge intravenous bonds
