AGGRESSION - Neural mechanisms
Limbic system
- Papez and McClean linked limbic system to emotional behaviour eg aggression
- Composed of hypothalamus, amygdala, hippocampus
- Amygdala = most important, responses to environmental threats and challenges
- How reactive amygdala is = good indicator of how aggressive you are (positively correlated)
Orbitofrontal cortex
- Damage to this causes loss of crucial behavioural guidance system
- Responses are impulsive and inappropriate
- Deficits of self regulation
Serotonin
- Denson et al (2012) found that serotonin disrupts orbitofrontal cortex, reducing self control
leading to an increase in impulsive behaviour eg aggression
Limitation of limbic system
- Non limbic structures also involved in aggression
- Orbitofrontal cortex not part of limbic system but works with amygdala in aggression
- Coccaro et al (2007), OC is reduced in those with psychiatric disorders that feature
aggression
- OFC disrupts impulse control
- Suggests regulation is more complex than theories focusing on the amygdala suggest
Strength of serotonin explanation
- Research into effects of drugs
- Drugs eg paroxetine that increase serotonin have been found to also reduce levels of
aggression
- Berman et al (2009) gave participants either placebo or dose of paroxetine
- Then participants gave or received electric shocks – paroxetine group consistently gave
fewer intense shocks than placebo group
- Evidence for causal link between serotonin function and aggression
Hormonal mechanisms
Testosterone
- Androgen, male sex hormone
- Plays important role in male aggression
- Development of male features
- Daly and Wilson (1988) said men become from aggression in time of development after 20
when testosterone levels are highest
- Giammanco et al (2005) – Castration studies and then injection back with testosterone in
rats
Progesterone
- Female ovarian hormone
- Important role in aggression in women
- Ziomkiewicz et al (2012) found a negative correlation between progesterone levels and self
reported aggression
- Low levels of P = high levels of aggression
, Strength
- Animal research by Giammanco
- Confirms role of testosterone
Limitation
- Mixed evidence for link between testosterone and aggression in humans
- Carre and Mehta (2011) developed dual-hormone hypothesis
- Claim high levels of testosterone lead to aggressive behaviour only when cortisol is low
- When cortisol is high, aggressive behaviour is inhibited
- Combined activity of T and C = better predictor
Ethological explanations
Adaptive functions of aggression
- Suggests aggression is adaptive, beneficial for survival
- Eg dominance hierarchies established, adaptive as access to more resources
Ritualistic aggression
- Series of behaviours carried out in a set order
- Lorenz (1966) observed fights between animals of same species = little damage
- Said intraspecific aggression end in appeasement – one animal is submissive to avoid
aggression
IRMs and FAPs
- IRM = inbuilt physiological process or structure in the brain
- Environmental stimulus triggers the IRM which then “releases” a specific sequence of
behaviours
- FAP = set sequence of behaviours as a result of IRM being activated
- 6 main features of FAPs:
- Stereotyped, unchanging series of behaviours
- Universal, same behaviour within the individuals of a species
- Unaffected by learning, same for every individual regardless of experience
- “Ballistic”, once behaviour is triggered it follows inevitable course and cannot be altered
until it is completed
- Single purpose, behaviour only occurs in specific situation
- Response to an identifiable specific sign stimulus
Tinbergens research
Procedure
- Male sticklebacks = territorial during mating season, develop red spot on underbelly
- If another male entera their territory = FAP is initiated
- Rep spot triggers the the IRM
Findings
- If model has red spot, male stickleback would be aggressive and attack it
- No red spot = no aggression
Limitation of FAPs
- Lorenz’s original few outdated, not unchanging
- Hunt (1973) pointed out FAPs are greatly influenced by environmental factors and learning
experiences
Limbic system
- Papez and McClean linked limbic system to emotional behaviour eg aggression
- Composed of hypothalamus, amygdala, hippocampus
- Amygdala = most important, responses to environmental threats and challenges
- How reactive amygdala is = good indicator of how aggressive you are (positively correlated)
Orbitofrontal cortex
- Damage to this causes loss of crucial behavioural guidance system
- Responses are impulsive and inappropriate
- Deficits of self regulation
Serotonin
- Denson et al (2012) found that serotonin disrupts orbitofrontal cortex, reducing self control
leading to an increase in impulsive behaviour eg aggression
Limitation of limbic system
- Non limbic structures also involved in aggression
- Orbitofrontal cortex not part of limbic system but works with amygdala in aggression
- Coccaro et al (2007), OC is reduced in those with psychiatric disorders that feature
aggression
- OFC disrupts impulse control
- Suggests regulation is more complex than theories focusing on the amygdala suggest
Strength of serotonin explanation
- Research into effects of drugs
- Drugs eg paroxetine that increase serotonin have been found to also reduce levels of
aggression
- Berman et al (2009) gave participants either placebo or dose of paroxetine
- Then participants gave or received electric shocks – paroxetine group consistently gave
fewer intense shocks than placebo group
- Evidence for causal link between serotonin function and aggression
Hormonal mechanisms
Testosterone
- Androgen, male sex hormone
- Plays important role in male aggression
- Development of male features
- Daly and Wilson (1988) said men become from aggression in time of development after 20
when testosterone levels are highest
- Giammanco et al (2005) – Castration studies and then injection back with testosterone in
rats
Progesterone
- Female ovarian hormone
- Important role in aggression in women
- Ziomkiewicz et al (2012) found a negative correlation between progesterone levels and self
reported aggression
- Low levels of P = high levels of aggression
, Strength
- Animal research by Giammanco
- Confirms role of testosterone
Limitation
- Mixed evidence for link between testosterone and aggression in humans
- Carre and Mehta (2011) developed dual-hormone hypothesis
- Claim high levels of testosterone lead to aggressive behaviour only when cortisol is low
- When cortisol is high, aggressive behaviour is inhibited
- Combined activity of T and C = better predictor
Ethological explanations
Adaptive functions of aggression
- Suggests aggression is adaptive, beneficial for survival
- Eg dominance hierarchies established, adaptive as access to more resources
Ritualistic aggression
- Series of behaviours carried out in a set order
- Lorenz (1966) observed fights between animals of same species = little damage
- Said intraspecific aggression end in appeasement – one animal is submissive to avoid
aggression
IRMs and FAPs
- IRM = inbuilt physiological process or structure in the brain
- Environmental stimulus triggers the IRM which then “releases” a specific sequence of
behaviours
- FAP = set sequence of behaviours as a result of IRM being activated
- 6 main features of FAPs:
- Stereotyped, unchanging series of behaviours
- Universal, same behaviour within the individuals of a species
- Unaffected by learning, same for every individual regardless of experience
- “Ballistic”, once behaviour is triggered it follows inevitable course and cannot be altered
until it is completed
- Single purpose, behaviour only occurs in specific situation
- Response to an identifiable specific sign stimulus
Tinbergens research
Procedure
- Male sticklebacks = territorial during mating season, develop red spot on underbelly
- If another male entera their territory = FAP is initiated
- Rep spot triggers the the IRM
Findings
- If model has red spot, male stickleback would be aggressive and attack it
- No red spot = no aggression
Limitation of FAPs
- Lorenz’s original few outdated, not unchanging
- Hunt (1973) pointed out FAPs are greatly influenced by environmental factors and learning
experiences
