neural and hormonal mechanisms in aggression
1. Definition of :
● Limbic system = structures in the brain including the hypothalamus and amygdala
thought to be closely involved in regulating emotional behaviour including
aggression.
● Serotonin = A neurotransmitter with widespread inhibitory effects throughout the
brain.
● Testosterone = A hormone produced in male testes and in smaller amounts in the
female ovaries, associated with aggressiveness.
2. Outline the roles of the limbic system and serotonin in aggression (6 marks)
The Limbic system helps coordinate behaviours that satisfy motivational and emotional
urges, such as aggression and fear. The Limbic system consists of the Amygdala and
Hippocampus. The Amygdala is responsible for quickly evaluating the emotional importance
of sensory information and prompting an appropriate response. The hippocampus is
involved with the information of LTM, so allows an animal to compare conditions of current
threat with similar past experiences. Impaired amygdala prevents the nervous system of
putting things into context, so may cause the amygdala to respond inappropriately to
sensory stimuli and this causes aggression.
Serotonin is a neurotransmitter that inhibits the firing of the amygdala. Low levels of
serotonin remove this inhibitory effect, meaning that individuals are less able to control
impulsive and aggressive behaviour.
3. Outline one research study into the role of neural or hormonal mechanisms in
aggression (6 marks)
Neural - Amygdala:
Gospic used a well-established laboratory method of assessing aggressive behaviour with a
game called the “/Ultimatum Game”. The researchers found that 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 the a BZ drug taken before the
game had 2 effects on the responses to unfair offers (splitting money unfairly): the number of
rejections halved and there was a decreased activity of the amygdala. This is strong
evidence of an association between reactive aggression and amygdala activity.
Neural - Serotonin:
Virkkunen et al. compared levels of a serotonin breakdown product in the cerebrospinal fluid
of violent impulsive and violent non-impulsive offenders. They found that the levels were
significantly lower in the impulsive offenders, and they also suffered from 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 in reactive aggression.
, Hormonal - Testosterone:
Hormonal research includes Animal studies from Giammancio have demonstrated
experimental increases in testosterone are related to greater aggressive behaviour in
several species and decreases leading to reductions in aggression.
Human studies from dolan et al used prison populations and found a positive correlation
between testosterone levels and aggressive behaviours in a sample of 60 male offenders in
the UK’s maximum security hospitals - suffered from a personality disorder and had a history
of impulsively violent behaviour.
4. Discuss the role of neural and/or hormonal mechanisms in aggression
(16marks)
The neural mechanisms in aggression involve the Limbic system and Serotonin.
Within the Limbic system is the Amygdala, which is responsible for quickly evaluating
the emotional importance of sensory information and prompting an appropriate
response, and the hippocampus is involved with the information of LTM, so allows an
animal to compare conditions of current threat with similar past experiences.
Serotonin is a neurotransmitter that inhibits the firing of the amygdala. Low levels of
serotonin remove this inhibitory effect, meaning that individuals are less able to
control impulsive and aggressive behaviour.
The hormonal mechanism involved in aggression is the role of Testosterone.
Testosterone is an androgen responsible for the development of masculine features
and regulates social behaviour via its influence on certain areas implicated in
aggression.
There is supporting evidence from Pardini et al who carried out a longitudinal study of
males from childhood to adulthood. At age 26 some had an MRI brain scan. They
found that ppts with lower amygdala volumes exhibited higher levels of aggression
and violence - this relationship remained even after the other extraneous variables
were controlled. This is clearly supporting evidence as it shows the amygdala is
responsible for mediating aggression because a small amygdala wouldn’t function
the same or as well as a normal sized one, so it wouldn’t accurately process
appropriate response to a stimulus. Also, brain scans have high internal validity,
therefore this evidence can be generalised and has higher external validity. However,
it is limited in that it does not demonstrate the exact cause and effect of aggression
and only shows a correlation which doesn’t exactly support the theory that the
amygdala influences behaviour as it may simply be the aggressive behaviours that
affect a person's amygdala and this is not clear in Pardini's study.
● Berman et al found that a group given a drug which enhances serotonin activity,
consistently gave fewer and less intense shocks in a lab-based game in response to
provocation, compared to a group given a placebo. This supports because it shows
how serotonin is involved with more calmer responses to a situation, they were less
impulsive. Therefore we can infer there is a link between serotonin and aggressive
behaviour. This is a lab study so eliminates the extraneous variables and we can
manipulate the IV and DV, therefore there is a higher internal validity. However,
1. Definition of :
● Limbic system = structures in the brain including the hypothalamus and amygdala
thought to be closely involved in regulating emotional behaviour including
aggression.
● Serotonin = A neurotransmitter with widespread inhibitory effects throughout the
brain.
● Testosterone = A hormone produced in male testes and in smaller amounts in the
female ovaries, associated with aggressiveness.
2. Outline the roles of the limbic system and serotonin in aggression (6 marks)
The Limbic system helps coordinate behaviours that satisfy motivational and emotional
urges, such as aggression and fear. The Limbic system consists of the Amygdala and
Hippocampus. The Amygdala is responsible for quickly evaluating the emotional importance
of sensory information and prompting an appropriate response. The hippocampus is
involved with the information of LTM, so allows an animal to compare conditions of current
threat with similar past experiences. Impaired amygdala prevents the nervous system of
putting things into context, so may cause the amygdala to respond inappropriately to
sensory stimuli and this causes aggression.
Serotonin is a neurotransmitter that inhibits the firing of the amygdala. Low levels of
serotonin remove this inhibitory effect, meaning that individuals are less able to control
impulsive and aggressive behaviour.
3. Outline one research study into the role of neural or hormonal mechanisms in
aggression (6 marks)
Neural - Amygdala:
Gospic used a well-established laboratory method of assessing aggressive behaviour with a
game called the “/Ultimatum Game”. The researchers found that 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 the a BZ drug taken before the
game had 2 effects on the responses to unfair offers (splitting money unfairly): the number of
rejections halved and there was a decreased activity of the amygdala. This is strong
evidence of an association between reactive aggression and amygdala activity.
Neural - Serotonin:
Virkkunen et al. compared levels of a serotonin breakdown product in the cerebrospinal fluid
of violent impulsive and violent non-impulsive offenders. They found that the levels were
significantly lower in the impulsive offenders, and they also suffered from 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 in reactive aggression.
, Hormonal - Testosterone:
Hormonal research includes Animal studies from Giammancio have demonstrated
experimental increases in testosterone are related to greater aggressive behaviour in
several species and decreases leading to reductions in aggression.
Human studies from dolan et al used prison populations and found a positive correlation
between testosterone levels and aggressive behaviours in a sample of 60 male offenders in
the UK’s maximum security hospitals - suffered from a personality disorder and had a history
of impulsively violent behaviour.
4. Discuss the role of neural and/or hormonal mechanisms in aggression
(16marks)
The neural mechanisms in aggression involve the Limbic system and Serotonin.
Within the Limbic system is the Amygdala, which is responsible for quickly evaluating
the emotional importance of sensory information and prompting an appropriate
response, and the hippocampus is involved with the information of LTM, so allows an
animal to compare conditions of current threat with similar past experiences.
Serotonin is a neurotransmitter that inhibits the firing of the amygdala. Low levels of
serotonin remove this inhibitory effect, meaning that individuals are less able to
control impulsive and aggressive behaviour.
The hormonal mechanism involved in aggression is the role of Testosterone.
Testosterone is an androgen responsible for the development of masculine features
and regulates social behaviour via its influence on certain areas implicated in
aggression.
There is supporting evidence from Pardini et al who carried out a longitudinal study of
males from childhood to adulthood. At age 26 some had an MRI brain scan. They
found that ppts with lower amygdala volumes exhibited higher levels of aggression
and violence - this relationship remained even after the other extraneous variables
were controlled. This is clearly supporting evidence as it shows the amygdala is
responsible for mediating aggression because a small amygdala wouldn’t function
the same or as well as a normal sized one, so it wouldn’t accurately process
appropriate response to a stimulus. Also, brain scans have high internal validity,
therefore this evidence can be generalised and has higher external validity. However,
it is limited in that it does not demonstrate the exact cause and effect of aggression
and only shows a correlation which doesn’t exactly support the theory that the
amygdala influences behaviour as it may simply be the aggressive behaviours that
affect a person's amygdala and this is not clear in Pardini's study.
● Berman et al found that a group given a drug which enhances serotonin activity,
consistently gave fewer and less intense shocks in a lab-based game in response to
provocation, compared to a group given a placebo. This supports because it shows
how serotonin is involved with more calmer responses to a situation, they were less
impulsive. Therefore we can infer there is a link between serotonin and aggressive
behaviour. This is a lab study so eliminates the extraneous variables and we can
manipulate the IV and DV, therefore there is a higher internal validity. However,
