Aggression Flashcards
What is the limbic system?
Subcortical structures in the brain (including the hypothalamus and amygdala) thought to be closely involved in regulating emotional behaviour including aggression
What is serotonin?
A neurotransmitter with widespread inhibitory effects throughout the brain. It has a key role in aggressive behaviour
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
What does the limbic system theory, by Papez, suggest about how aggression is caused?
The reactivity of the amygdala in humans has proven to be an important predictor of aggression
What is the amygdala?
- Most important structure
- Has a key role in humans and nonhuman animals in how an organism assesses and responds to environmental threats and challenges
What did Katarina Gospic et al do?
- Lab method
- Ultimatum Game
- 2 players
- The proposer offers to split money in a certain way with the responder
- If the responder accepts, the money is split as proposed
- But if the responder rejects the offer, both receive nothing
- Participants in this study played as responders while having their brains scanned by fMRI which highlights activity in different areas of the brain
What did Katarina Gospic et al find?
- When responders rejected unfair offers (an aggressive reaction to social provocation) scans revealed a fast and heightened response by the amygdala
- They also found that a benzodiazepine drug (which reduces arousal of the automatic nervous system) taken before the game had 2 effects on responses to unfair offers. It halved the number of rejections (i.e. reduced aggression) and decreased the activity of the amygdala.
Name strong evidence for the association between reactive aggression and amygdala activity.
Katarina Gospic et al
How does serotonin cause aggression?
Decreased serotonin may well disturb the reduced firing of neurons in the orbitofrontal cortex when there are normal levels of serotonin, reducing self-control and leading to an increase in impulsive behaviour including aggression
What did Matti Virkkunen et al do?
- Compared levels of a serotonin breakdown product in the cerebrospinal fluid of violent impulsive and violent non-impulsive offenders.
What did Matti Virkkunen et al find?
- The levels of a serotonin breakdown product in the cerebrospinal fluid were significantly lower in the impulsive offenders
- They also suffered from more sleep irregularities
- This is significant because serotonin regulates sleep patterns. Disturbance of this pattern strongly implies some disruption of serotonin functioning, further supporting the role of serotonin
Name supporting evidence for the role of serotonin in aggression.
Matti Virkkunen et al
How does testosterone cause aggression?
- It is a reliable observation that males are generally more aggressive than females
- Testosterone is responsible for the development of masculine features and also has a role in regulating social behaviour via its influence on certain areas of the brain implicated in aggression
Name an animal study of the influence of testosterone on aggression.
Giammanco et al
What did Giammanco et al do?
- Demonstrated experimental increase in testosterone is related to greater aggressive behaviour in several species (and the converse is true, with decreases leading to reductions in aggression in castration studies)
What does the MAOA gene do?
- Breaks down 3 neurotransmitters (noradrenaline, serotonin, dopamine) in the brain after they have carried nerve impulses from one cell to another
What are the 2 different forms of the MAOA gene?
- Low activity (MAOA-L)
- High activity (MAOA-H)
Which form of the MAOA gene is associated with high aggression?
Low activity (MAOA-L)
What did Stuart et al do?
Studied 97 males convicted of intimate partner violence (IPV) and found that the most violent of them had low activity MAOA
What did Frazzetto et al do?
Found an association between asocial aggression and low activity MAOA but only in those who had experienced trauma in the first 15 years of life
What is the ethological explanation of aggression?
Aggression is beneficial to survival
Why is aggression beneficial to survival?
- Reduces competition
- Establishes dominance hierarchies
How does aggression reduce competition?
A defeated animal is rarely killed but rather forced to establish territory elsewhere, this means that members of a species are spread out over a wider area and have to discover resources in a different places which reduces competition pressures and the possibility of starvation
What is ritualistic aggression?
A series of behaviours carried out in set order
What did Lorenz find concerning ritualistic aggression?
Early observations of fights between animals of the same species found how little actual physical damage was done
- Most aggressive encounters consisted mainly of a period of ritualistic signalling
- Furthermore, Lorenz pointed out that intra-species aggressive confrontations end with ritual appeasement displays (showing neck)
- These indicate acceptance of defeat and inhibit aggressive behaviour in the victor, preventing any damage to the loser
How is ritualistic aggression adaptive?
If every aggressive encounter ended with the death of one of the combatants, that could threaten the existence of the species
What is an innate releasing mechanism (IRM)?
A biological structure or process (e.g. in the brain) which is triggered by an external stimulus that in turn triggers a fixed action pattern
What is a fixed action pattern (FAP)?
A sequence of stereotyped pre-programmed behaviours triggered by an innate releasing mechanism (IRM)
What are the 6 main features of a fixed action pattern (FAP)?
- Stereotyped
- Universal
- Unaffected by learning
- Ballistic- the whole sequence of behaviours must follow once a FAP is triggered
- Single purposed
- Response to identifiable specific sign stimulus
What did Tinbergen do?
- Presented male sticklebacks during mating season with a series of wooden models of different shapes
- Regardless of shape, if the model has a red spot the stickleback would display a FAP
- If there was no red spot, there was no aggression even if the model looked like a stickleback
What is the evolutionary explanation of aggression?
Explaining aggression in terms of changes in species over millions of years; characteristics that enhance survival and reproduction are naturally selected
Why are males aggressive according to the evolutionary explanation?
Threat of cuckoldry so they use mate retention strategies, sexual jealousy and bullying
What are the 2 mate retention strategies?
- Direct guarding
- Negative Inducements
What is direct guarding?
Male vigilance over a partner’s behaviour