AGGRESSION;
Types of aggression:
1) Proactive = cold, planned and unprovoked aggression.
2) Reactive = Angry, retaliation, In the heat of the moment, Impulsive aggression.
tt,uraf ,ad borrnea•f mech,aflDlli
Neural mechanisms: Limbic system, serotonin.
Limbic system: Amygdala, hlppocampus.
Hormonal: Testosterone.
Limbic System:
The amygdala Is responsible for the evaluation of sensory information and providing an appropriate response. E.g. what is a
threat, how to respond .
1) Electrical stimulation can lead to an aggressive response.
2) Reduced amygdala volume can lead to aggression.
The hlppocampus is involved in the information of long term memories. E.g. humans/animals can compare current threats with
past experiences and respond appropriately.
1) Damage (e.g. asymmetry), might impair the ability of the hippocampus to work with the amygdala in order to produce
an appropriate response to the situation.
EV/Example: Charles Whitman: had a tumor pressing onto his amygdala which reduced the volume of it, he had proactive
aggressive behaviour.
EV/Example: Marl<: had a tumor pressing onto his amygdala and hypothalamus, his behaviour was reactive as he had
impulsive aggression.
EV/AMYGDALA:
(+) Animal studies have shown that if their amygdala is electrically stimulated then they will respond aggressively, this was
shown on bulls, cats and mice in which electrodes are connected to them and if their amygdala is electrically stimulated this
leads to rage and aggression. (-) However, the findings from animal research cannot be extrapolated due to qualitatively
complex differences between animals and humans.
EV/HIPPOCAMPUS:
(+) Raine had found that individuals who had asymmetries on the hippocampus were also aggressive, especially those who
showed impulsive aggression. Suggesting that this could impair the ability of the hippocampus and amygdala to work together
to be able to process emotional information appropriately. Providing support for the neural mechanisms in aggression. (-)
However, Raine's study lacked population validity as his research involved violent criminals, these individuals do not represent
the general population.
(-) Research indicates that the OFC which is nol'a part of the limbic system has a part to play in aggression. The OFC is
thought to be involved in self-control and inhibition of anger.
Serotonin:
Low levels of serotonin = aggression.
serotonin has a calming effect, and allows the person to have greater self-control by inhibiting the firing of neurons on the OFC.
Low levels of serotonin means that individuals cannot control their impulsive and aggressive behaviour, they cannot anticipate
risk so they impulsively engage in risky and aggressive behaviour.
EV:
(+) Animal studies on dogs, blood samples taken from 80 dogs that were referred to the vets for aggression, these dogs had
lower levels of serotonin compared to non-aggressive dogs. (-) However, it is hard to extrapolate findings from animals to
humans as humans are qualitatively different.
Testosterone:
The primary sex hormone within males which is produced by the testes, several studies have found that high testosterone is
correlated with increased aggression and that low testosterone is correlated with decreased aggression.
E .g . Animal studies have found that injecting female rats with testosterone made them behave more aggressively.
Genetic facfOf!i
MAOA-L Gene
Twin studies
, Adoption studies.
Twin studies:
Coccaro: studies adult male DZ and MZ twins, and the aggressive behaviour displayed, the aggressive behaviour was direct
physical assault.
Found a concordance rate of 50% between MZ twins and 19% between DZ twins.
This suggests that as MZ twins are Identical and share 100% of their genes that there is a genetic link.
EV:
(-) However, researchers cannot rule out the environment. The social learning theory would suggest that due to imitation and
nurture, children may grow up to be aggressive from watching their friend or family members also be aggressive, if aggression
was purely genetic there would be a 100% concordance rate fo rMZ twins but there was only a 50% concordance rate
suggesting that the environment has an influence.
Adoption studies:
Research into adoption studies has found that children who had aggressive biological parents were likely to grow up and also
have a criminal conviction. Research found a significant positive correlation between the number of convictions among
biological parents and the number of criminal convictions, among their adopted sons, providing evidence for a genetic
explanation.
EV:
(-)However, a positive correlation does not show cause and effect, as it is important to know when each child was adopted and
if they had experienced any aggression from their biological parents before they were adopted which was the reason for
them
being adopted, children may also grow up to be a criminal and show aggressive behaviour if they have feelings of being
abandoned as a child.
MAOAGene:
Inherit the faulty gene "warrior gene•, which causes the activity of the enzyme MAOA to become low. The enzyme MAOA is
responsible for the metabolism of neurotransmitters after they have been released from the synapse. Due to the MAOA enzyme
having low activity this means that it cannot metabolise the neurotransmitters, this leads to the high levels of serotonin,
dopamine and noradrenaline.
High levels of serotonin = an increase in impulsive behaviour.
High levels of noradrenaline = lead to overreaction
High levels of dopamine = means that when aggressive acts are carried out there is an increase of a feeling of reward.
EV:
(-) However, Caspi argues the-diathesis stress modef;Jhat genes influence the environment and that the environment
influences genes, so a genetic predisposition and an environmental trigger can lead to aggression.
fthctoetslf 01Qfflo1flpo, Af@P9CMr1lpn (ANJUALSI.
Study of animal behaviour
Aggression is adaptive (benefits outweigh the costs)
Sign stimulus
Innate releasing mechanisms
Fixed action patterns (SUB)
'' , '
a
The main function of aggression -is to be adaptive, as 1t is beneficial for sUnlival. As this means that they are able to establish
dominance hierarchy, this will allow the alpha to gain resources, food and a mate.
Often within the same species there is ritualistic aggression, aggressive encounters between animals often involves ritualistic
to
signalling:soch as sounds and·gestures. They often·end with an appeasement display from the loser to prevent any damage
them and show submission. Ritualistic aggression is done so that their species will not go extinct, this allows for them to gain
status and dominance but through ritualistic aggression so that they won't go extinct.
IRM's =:inbuilt biological processes, which respond to an external stimuli which initiates a FAP.
FAP = a sequence of stereotypes/preprogrammed behaviours which are triggered by an IRM. '
An IRM is an inbuilt biological process which responds to external stimuli or sign stimulus (such as physical appearance), this
triggers a FAP, which are a sequence of behaviours, once the behaviour is triggered it cannot be stopped, they occur in the
same species.
These sequences of behaviours are stereotyped (occurs In the same way), universal (the same in all conspecifics), ballistic
{once triggered it cannot be stopped).
Types of aggression:
1) Proactive = cold, planned and unprovoked aggression.
2) Reactive = Angry, retaliation, In the heat of the moment, Impulsive aggression.
tt,uraf ,ad borrnea•f mech,aflDlli
Neural mechanisms: Limbic system, serotonin.
Limbic system: Amygdala, hlppocampus.
Hormonal: Testosterone.
Limbic System:
The amygdala Is responsible for the evaluation of sensory information and providing an appropriate response. E.g. what is a
threat, how to respond .
1) Electrical stimulation can lead to an aggressive response.
2) Reduced amygdala volume can lead to aggression.
The hlppocampus is involved in the information of long term memories. E.g. humans/animals can compare current threats with
past experiences and respond appropriately.
1) Damage (e.g. asymmetry), might impair the ability of the hippocampus to work with the amygdala in order to produce
an appropriate response to the situation.
EV/Example: Charles Whitman: had a tumor pressing onto his amygdala which reduced the volume of it, he had proactive
aggressive behaviour.
EV/Example: Marl<: had a tumor pressing onto his amygdala and hypothalamus, his behaviour was reactive as he had
impulsive aggression.
EV/AMYGDALA:
(+) Animal studies have shown that if their amygdala is electrically stimulated then they will respond aggressively, this was
shown on bulls, cats and mice in which electrodes are connected to them and if their amygdala is electrically stimulated this
leads to rage and aggression. (-) However, the findings from animal research cannot be extrapolated due to qualitatively
complex differences between animals and humans.
EV/HIPPOCAMPUS:
(+) Raine had found that individuals who had asymmetries on the hippocampus were also aggressive, especially those who
showed impulsive aggression. Suggesting that this could impair the ability of the hippocampus and amygdala to work together
to be able to process emotional information appropriately. Providing support for the neural mechanisms in aggression. (-)
However, Raine's study lacked population validity as his research involved violent criminals, these individuals do not represent
the general population.
(-) Research indicates that the OFC which is nol'a part of the limbic system has a part to play in aggression. The OFC is
thought to be involved in self-control and inhibition of anger.
Serotonin:
Low levels of serotonin = aggression.
serotonin has a calming effect, and allows the person to have greater self-control by inhibiting the firing of neurons on the OFC.
Low levels of serotonin means that individuals cannot control their impulsive and aggressive behaviour, they cannot anticipate
risk so they impulsively engage in risky and aggressive behaviour.
EV:
(+) Animal studies on dogs, blood samples taken from 80 dogs that were referred to the vets for aggression, these dogs had
lower levels of serotonin compared to non-aggressive dogs. (-) However, it is hard to extrapolate findings from animals to
humans as humans are qualitatively different.
Testosterone:
The primary sex hormone within males which is produced by the testes, several studies have found that high testosterone is
correlated with increased aggression and that low testosterone is correlated with decreased aggression.
E .g . Animal studies have found that injecting female rats with testosterone made them behave more aggressively.
Genetic facfOf!i
MAOA-L Gene
Twin studies
, Adoption studies.
Twin studies:
Coccaro: studies adult male DZ and MZ twins, and the aggressive behaviour displayed, the aggressive behaviour was direct
physical assault.
Found a concordance rate of 50% between MZ twins and 19% between DZ twins.
This suggests that as MZ twins are Identical and share 100% of their genes that there is a genetic link.
EV:
(-) However, researchers cannot rule out the environment. The social learning theory would suggest that due to imitation and
nurture, children may grow up to be aggressive from watching their friend or family members also be aggressive, if aggression
was purely genetic there would be a 100% concordance rate fo rMZ twins but there was only a 50% concordance rate
suggesting that the environment has an influence.
Adoption studies:
Research into adoption studies has found that children who had aggressive biological parents were likely to grow up and also
have a criminal conviction. Research found a significant positive correlation between the number of convictions among
biological parents and the number of criminal convictions, among their adopted sons, providing evidence for a genetic
explanation.
EV:
(-)However, a positive correlation does not show cause and effect, as it is important to know when each child was adopted and
if they had experienced any aggression from their biological parents before they were adopted which was the reason for
them
being adopted, children may also grow up to be a criminal and show aggressive behaviour if they have feelings of being
abandoned as a child.
MAOAGene:
Inherit the faulty gene "warrior gene•, which causes the activity of the enzyme MAOA to become low. The enzyme MAOA is
responsible for the metabolism of neurotransmitters after they have been released from the synapse. Due to the MAOA enzyme
having low activity this means that it cannot metabolise the neurotransmitters, this leads to the high levels of serotonin,
dopamine and noradrenaline.
High levels of serotonin = an increase in impulsive behaviour.
High levels of noradrenaline = lead to overreaction
High levels of dopamine = means that when aggressive acts are carried out there is an increase of a feeling of reward.
EV:
(-) However, Caspi argues the-diathesis stress modef;Jhat genes influence the environment and that the environment
influences genes, so a genetic predisposition and an environmental trigger can lead to aggression.
fthctoetslf 01Qfflo1flpo, Af@P9CMr1lpn (ANJUALSI.
Study of animal behaviour
Aggression is adaptive (benefits outweigh the costs)
Sign stimulus
Innate releasing mechanisms
Fixed action patterns (SUB)
'' , '
a
The main function of aggression -is to be adaptive, as 1t is beneficial for sUnlival. As this means that they are able to establish
dominance hierarchy, this will allow the alpha to gain resources, food and a mate.
Often within the same species there is ritualistic aggression, aggressive encounters between animals often involves ritualistic
to
signalling:soch as sounds and·gestures. They often·end with an appeasement display from the loser to prevent any damage
them and show submission. Ritualistic aggression is done so that their species will not go extinct, this allows for them to gain
status and dominance but through ritualistic aggression so that they won't go extinct.
IRM's =:inbuilt biological processes, which respond to an external stimuli which initiates a FAP.
FAP = a sequence of stereotypes/preprogrammed behaviours which are triggered by an IRM. '
An IRM is an inbuilt biological process which responds to external stimuli or sign stimulus (such as physical appearance), this
triggers a FAP, which are a sequence of behaviours, once the behaviour is triggered it cannot be stopped, they occur in the
same species.
These sequences of behaviours are stereotyped (occurs In the same way), universal (the same in all conspecifics), ballistic
{once triggered it cannot be stopped).
