Aggression
,Neural mechanisms
Biological models, assume that aggression is located within biological makeup of individual rather
than in the environment around them
Limbic Syem
Set of subcortical structures in the brain (including the amygdala and hypothalamus) that is
involved in regulating emotional behaviour
• the speed and sensitivity of limbic system responses to stimulus are important predictors of
aggressive behaviour in humans
• if limbic system is too fast and sensitive -> aggression
AMYGDALA:
• responsible for attaching emotional significance to sensory information
• Key role in how we assess and respond to environmental threats
• fMRI scans - heightened amygdala activity during aggressive responses
• Stimulation of amygdala Increases or decreases aggression
HYPOTHALAMUS:
• responsible for regulation of the autonomic nervous system
• Which intern regulates responses to emotional circumstances
• Damage to this area can result in inappropriate aggressive response to a threat
• can make you more impulsive and therefore aggressive
• also has connections to prefrontal cortex
• Involved in the anticipation of rewards
• Regulate social behaviour and aggressive responses
• Damage would reduce the inhibition of the amygdala resulting in higher levels of aggression
• limbic system plays key role in how an organism responds to environmental threats and
challenges
• Key factor in whether we respond, aggressively or not too external stimulus
• REACTIVE AGGRESSION
, Strengths Weaknesses
1. LE DOUX // animal research - EXTRAPOLATION
• electrical stimulation to the
amygdala // reductionist
• in lab animals, led to fear and rage // lacks eco val
responses
• Suggest that the amygdala must be
linked to aggression,
• supporting the role of the limbic
system In aggression
2. NARABAYASHI ET AL // leads to practical applications
• 43 out of 51 patients who had • removal of amygdala
amygdala removed
• Showed more normal social
behaviour afterwards 1. ROLE OF LIMBIC SYSTEM NOT CLEAR CUT
• Including reduced aggression • limbic system made of many components
• Suggest amygdala play role in • Not clear, which part may be implicated in
aggression aggression
• Amygdala removal removes • Could be interaction between components
aggression of the system with other components of the
brain
• Research suggest a Magdala operates with
orbitofrontal cortex (not part of limbic
system)
• Involved in self-control, impulse regulation
and inhibition of aggressive behaviour
• COCCARRO et al
• psychiatric patients with disorders that
feature aggression
• Commonly have reduced activity in OFC
• Suggests regulation of of agg cannot be
explained by limbic system alone
• Highly complex
• Role of limbic system needs further
investigation
• implications : criminal behaviour
, Serotonin
STILL NEURAL EXPL
A neurotransmitter involved in communication of impulses between neurons
• serotonin deficiency hypothesis
• normally works on the frontal areas of brain to inhibit generation of impulses in neurons in
the amygdala
• The part of the limbic system that controls fear, anger and other emotional responses
• Serotonin has a calming influence
• Associated with greater behavioural control
• however, have low levels of serotonin:
• can't control impulsivity
• May engage in more aggressive behaviour
• serotonin also regulates prefrontal cortex
• Affect our response to external stimuli
• More aggressive easily
• can't anticipate risk + impulsively, engage in aggressive behaviour
Strengths Weaknesses
1. RALEIGH ET AL 1. CONFLICTING EVIDENCE
• studied monkeys • HUBER:
• found that individuals fed on • Increasing serotonin levels in crayfish
experimental diet high in tryptophan increase the length of time they continued
• (inc serotonin lvls in brain) fighting for
• Showed decreased levels of • Continued to fight beyond point at which they
aggression would normally cease
• Individuals fed on diet low in • Suggest level of aggression experiencing wa
tryptophan greater
• Increased aggression • Or natural response overridden
• evidence for role of serotonin in • still suggest serotonin plays part in aggressio
aggressive behaviours as it suggest
causal effect
• fits major features of science
• practical applications // animal research
• increases tryptophan diet to decrease • far on phylogenetic scale
aggression
,Neural mechanisms
Biological models, assume that aggression is located within biological makeup of individual rather
than in the environment around them
Limbic Syem
Set of subcortical structures in the brain (including the amygdala and hypothalamus) that is
involved in regulating emotional behaviour
• the speed and sensitivity of limbic system responses to stimulus are important predictors of
aggressive behaviour in humans
• if limbic system is too fast and sensitive -> aggression
AMYGDALA:
• responsible for attaching emotional significance to sensory information
• Key role in how we assess and respond to environmental threats
• fMRI scans - heightened amygdala activity during aggressive responses
• Stimulation of amygdala Increases or decreases aggression
HYPOTHALAMUS:
• responsible for regulation of the autonomic nervous system
• Which intern regulates responses to emotional circumstances
• Damage to this area can result in inappropriate aggressive response to a threat
• can make you more impulsive and therefore aggressive
• also has connections to prefrontal cortex
• Involved in the anticipation of rewards
• Regulate social behaviour and aggressive responses
• Damage would reduce the inhibition of the amygdala resulting in higher levels of aggression
• limbic system plays key role in how an organism responds to environmental threats and
challenges
• Key factor in whether we respond, aggressively or not too external stimulus
• REACTIVE AGGRESSION
, Strengths Weaknesses
1. LE DOUX // animal research - EXTRAPOLATION
• electrical stimulation to the
amygdala // reductionist
• in lab animals, led to fear and rage // lacks eco val
responses
• Suggest that the amygdala must be
linked to aggression,
• supporting the role of the limbic
system In aggression
2. NARABAYASHI ET AL // leads to practical applications
• 43 out of 51 patients who had • removal of amygdala
amygdala removed
• Showed more normal social
behaviour afterwards 1. ROLE OF LIMBIC SYSTEM NOT CLEAR CUT
• Including reduced aggression • limbic system made of many components
• Suggest amygdala play role in • Not clear, which part may be implicated in
aggression aggression
• Amygdala removal removes • Could be interaction between components
aggression of the system with other components of the
brain
• Research suggest a Magdala operates with
orbitofrontal cortex (not part of limbic
system)
• Involved in self-control, impulse regulation
and inhibition of aggressive behaviour
• COCCARRO et al
• psychiatric patients with disorders that
feature aggression
• Commonly have reduced activity in OFC
• Suggests regulation of of agg cannot be
explained by limbic system alone
• Highly complex
• Role of limbic system needs further
investigation
• implications : criminal behaviour
, Serotonin
STILL NEURAL EXPL
A neurotransmitter involved in communication of impulses between neurons
• serotonin deficiency hypothesis
• normally works on the frontal areas of brain to inhibit generation of impulses in neurons in
the amygdala
• The part of the limbic system that controls fear, anger and other emotional responses
• Serotonin has a calming influence
• Associated with greater behavioural control
• however, have low levels of serotonin:
• can't control impulsivity
• May engage in more aggressive behaviour
• serotonin also regulates prefrontal cortex
• Affect our response to external stimuli
• More aggressive easily
• can't anticipate risk + impulsively, engage in aggressive behaviour
Strengths Weaknesses
1. RALEIGH ET AL 1. CONFLICTING EVIDENCE
• studied monkeys • HUBER:
• found that individuals fed on • Increasing serotonin levels in crayfish
experimental diet high in tryptophan increase the length of time they continued
• (inc serotonin lvls in brain) fighting for
• Showed decreased levels of • Continued to fight beyond point at which they
aggression would normally cease
• Individuals fed on diet low in • Suggest level of aggression experiencing wa
tryptophan greater
• Increased aggression • Or natural response overridden
• evidence for role of serotonin in • still suggest serotonin plays part in aggressio
aggressive behaviours as it suggest
causal effect
• fits major features of science
• practical applications // animal research
• increases tryptophan diet to decrease • far on phylogenetic scale
aggression
