Paper3: Aggression Flashcards
- Neural Mechanisms of Aggression
What is the difference in hot- and cold-blooded aggression?
And the case studies assossiated with these
Hot (reactive aggression): an impulsive behavior coupled with physiological arousal
- Case:Tony Martin shot 3 intruders, killed one (a 16 year old) following burglaries at his home. Initially, sentenced to life imprisonment.
Cold: a premeditated way of getting what you want
- Rape and murder
- Case: the Moors Murders: Ian Brady and Myra Hindley
- Forensic psychology is primarily concerned with this type.
- Neural Mechanisms of Aggression
What are the brain regions associated with the limbic system?
Includes: Amygdala, hippocampus and thalamus/hypothalamus, OFC
- Neural Mechanisms of Aggression
What is a key role of the limbic circuit?
Maclean: limbic system in the mammalian brain is the centre of emotion and learning
Collection of structures in the centre of the brain.
One of its functions is to processes emotional responses Such as aggression.
- Neural Mechanisms of Aggression
What is the limbic circuit also known as?
Papez circuit as Papez first identified the contents of the limbic system
- Neural Mechanisms of Aggression
What are three key regions of the limbic system involved in aggression?
Orbital frontal cortex - controls executive function (decision making) which tries to control aggression produced by the limbic system.
Amygdala - linked to the production of aggressive behaviour, FMRI’s show increased activity during aggressive responses. (Gospic)
Hypothalamus - role in integrating and expressing emotional responses, it can trigger aggressive behaviours as part of the fight or flight response.
- Neural Mechanisms of Aggression
What evidence is there for a role of serotonin in violent behaviour?
Animal studies:
What is the link between Kluver & Bucy’s (1937) research in animals and Kluver-Bucy syndrome
They found that amygdala destruction in a dominant monkey resulted in the loss of social dominance.
Klüver-Bucy Syndrome, a rare neuropsychiatric disorder caused by bilateral temporal lobe lesions (affecting the hippocampus and amygdala), leads to symptoms like placidity.
An amygdala-lesioned animal immediately grabbed a grape near a rubber snake (A) and then explored the snake (B), behavior that is atypical in normal animals, which instinctively avoid snakes.
- Neural Mechanisms of Aggression
What did Mark & Ervin (1970) report in a patient receiving stimulation to her amygdala?
Stimulation near the amygdala produces fear, anxiety, defensive, and sometimes violent behaviour.
found a woman receiving painless stimulation to her amygdala became enraged and smashed her guitar against the wall
- Neural Mechanisms of Aggression
Explain the research by Gospic et al. (2011), and how it sheds light on the role of the limbic system in aggression.
Participants played The Ultimatum Game, where Subject A was the Proposer and Subject B the Responder, who experienced mild provocation.
MRI scans showed increased amygdala activity when Subject B rejected offers. However, benzodiazepines, which reduce anxiety, halved rejection rates and lowered amygdala activity, suggesting a link between reactive aggression and amygdala function.
- Neural Mechanisms of Aggression
Explain the relationship between serotonin and aggression.
- Serotonin has inhibitory effects on the brain - slowing down neuronal activity
- Aggression in humans and animals is associated with low levels of serotonin
- Normal levels in the OFC reduce the firing of neurons and allow for a greater degree of behavioural self control
- Decreased levels disturb this mechanism reducing self control and increasing impulsive behaviour including aggression
- Neural Mechanisms of Aggression
What evidence is there for a role of serotonin in violent behaviour?
1. Animal Studies
pharmacologically blocking or genetically modifying 5-HT2A receptors.
mice with a deletion of the gene responsible for 5-HT2A expression exhibit less aggressive behaviour compared to typical mice. Stimulation this receptor subtype can lead to aggression, especially when the animal perceives threat or competition
- Neural Mechanisms of Aggression
What evidence is there for a role of serotonin in violent behaviour?
- Anti-psychotics
Risperidone and Olanzapine block the 5-Ht2A receptor, and has been shown to reduce aggression in patients with schizophrenia or dementia
- Neural Mechanisms of Aggression
What evidence is there for a role of serotonin in violent behaviour?
- Serotonergic Metabolites
Virkunnen compared cerebrospinal fluid levels of the serotonin metabolite 5-HIAA in violent impulsive and non-impulsive offenders. Impulsive offenders had significantly lower levels, indicating reduced serotonin activity linked to poor impulse control
- Neural Mechanisms of Aggression
What evidence is there for a role of serotonin in violent behaviour?
- Serotonin-Depletion Studies
Passamonti used acute tryptophan depletion (ATD) to lower serotonin levels and found reduced connectivity between the PFC and amygdala when participants viewed angry faces, suggesting low serotonin weakens PFC control over aggression-related amygdala responses.
- Neural Mechanisms of Aggression
What evidence is there for a role of serotonin in violent behaviour?
5. Post-Mortem Studies
Rosell and Siever reviewed post moretem studies indicating that individuals with histories of impulsive aggression show an upregulation of 5-HT2A receptors (perhaps compensating for low serotonin) in the PFC, particularly in the OFC.
- Neural Mechanisms of Aggression
2 strengths and 1 limit
P: A strength of the limbic system’s involvement in aggression is case study evidence showing that damage to it can lead to aggressive behaviors.
Eg: Burns & Swerdlow reported a case where pedophilia developed after a tumor in the orbitofrontal cortex, resolving after surgery.
Ex: Similarly, Sumer’s case of a 14-year-old girl’s extreme aggression was linked to a tumor pressing on her amygdala.
C: However, case studies may not be generalizable, and it’s important to identify the specific amygdala connections affected.
L: while case studies support the link between limbic activity and aggression, they should be interpreted with caution and corroborated by other research.
P: A strength of the serotonin explanation for aggression comes from drug research showing that increasing serotonin reduces aggression.
Eg: Berman (2009) found that participants given paroxetine (boosting serotonin) gave fewer and less intense shocks in a lab game, especially those with a history of aggression.
Ex: This suggests increased serotonin reduces aggression in a controlled setting, strengthening evidence beyond correlational studies.
C: However, the lack of direct measures of serotonergic activity makes it unclear whether reduced aggression is due to serotonin or other effects of paroxetine.
L: These findings do not conclusively establish a causal link, potentially lowering internal validity. Future research should use neuroimaging or biochemical assays to measure serotonin receptor activity.
P: A limitation of research on the neural basis of aggression is that much of it is correlational, limiting causality.
Eg: Correlational studies are often necessary due to ethical constraints, as directly provoking aggression would risk harm to participants. Researchers rely on brain scans to observe links between aggression and brain structures like the amygdala or OFC.
Ex: However, without experimental manipulation, it’s unclear if changes in these areas cause aggression or result from it.
L: This raises the possibility of a third variable, such as fluctuating neurotransmitter levels, influencing both aggression and neural changes. Consequently, the correlational nature limits conclusions about causality so lowers the internal validity
- Hormonal mechanisms of aggression
What is androgen?
A male sex hormone responsible for masculine features eg: testosterone
- Hormonal mechanisms of aggression
Suggest 3 reasons why testosterone is thought to have a role in aggression in males.
males are generally more aggressive than females
-testosterone has a role for regulating social behaviour via its influence on the brain implicated with aggression
-Daly and Wilson: Aggression is highest in males 20+ years old when testosterone peaks
- Hormonal mechanisms of aggression
What animal data (causation) support the role of testosterone in aggression?
Giammanco: experimental increases in testosterone increased aggression and the removal of testes decreased aggression
- Hormonal mechanisms of aggression
What did Dolan et al.’s (2001) study find with regard to testosterone and aggression?
positive correlation between testosterone levels and aggression in 60 male offenders in UK maximum security hospitals. The men mostly had personality disorders and a history of impulsive (reactive) violent behaviour
- Hormonal mechanisms of aggression
What evidence is there for the role of hormones in female aggression?
progesterone plays a role in aggression in women
Levels of progesterone vary during ovulation cycle are lowest after menstruation
Ziomkiewick found a negative correlation between progesterone and aggression in women
- Hormonal mechanisms of aggression
1 strength and 1 limit
P: A strength of the hormonal explanation of aggression is supporting empirical evidence.
Eg: Mehta and Josephs (2006) measured testosterone levels before and after a competitive game loss. Of those with increased testosterone, 73% chose to re-challenge the winners (operationalized as aggression), compared to 22% whose testosterone decreased.
Ex: This suggests that increased testosterone after a status loss promotes aggression, supporting its role in context-dependent aggression.
C: However, the study defines aggression narrowly, excluding real-world verbal and physical confrontations.
L: While testosterone may influence aggression in competitive settings, its effects may vary in broader social contexts
P: A limitation of the explanation that increased testosterone levels increase aggression is that it seems incomplete.
Eg: Carre and Mehta (2011) proposed the dual-hormone hypothesis, which suggests high testosterone only promotes aggression when cortisol levels are low. When cortisol is high, it inhibits testosterone’s effect on aggression.
Ex: Explaining aggression through a single hormone may be overly reductionist, as multiple hormonal and social factors interact to influence behavior.
L: This limits the validity of testosterone-based explanations, as it overlooks cortisol’s moderating role. A more nuanced, multi-hormone approach, accounting for environmental factors, may better reflect the biological basis of aggression.
- Genetic factors of aggression
What are the 4 broad approaches to the study of the influence of genetics and environment on behaviour (such as aggression)
1) twin studies
2) adoption studies
3) candidate studies
4) family studies
- Genetic factors of aggression
Explain the rationale for twin studies
- MZ twins share all their genes, so differences between them are assumed to be due to environmental factors.
- If both MZ twins are highly aggressive, it suggests a genetic influence.
- The degree of similarity between twins on a trait is called the concordance rate.
- Concordance rates measure the presence of the same trait in both members of a twin pair.
- These rates are often compared with DZ twins, who are 50% genetically related.
- Higher concordance rates in MZ twins suggest a heritable component to the trait being measured.
- Genetic factors of aggression
twin studies:
What did Coccaro et al. (1997) show in their twin studies
He found MZ twins had concordance rates of 50% and DZ at 19% suggesting because MZ twins share the same DNA there’s a genetic component to aggression and DZ twins share only 50% of their DNA
Verbal aggression was also 28% in MZ and 7% DZ.