Aggression notes
Neural and hormonal mechanisms
The limbic system lies beneath the cortex involving the amygdala and the hippocampus
mediates motivated behaviours, emotional states and memory processes.
Amygdala
Maybe part of area responsible for emotion and aggression based on research by Pardini
2014 who conducted a longitudinal study of 56 males with histories of violence, these males
had an MRI aged 26 and it showed a that smaller the amygdala the more aggressive the
criminal is.
Hippocampus
Helps to form LTMs thus allowing us to respond to current threat situations with experience
(e.g. is this person dangerous or not), misunderstanding of this sensory info will lead to the
amygdala to respond inappropriately this is supported by Adrian Raine 2004 who viewed
psychopaths under an MRI and found that they had asymmetries in the hippocampi volume
which in turn restricted communication between the hippocampi and the amygdala, which
led to inappropriate responses (aggressive behaviour).
Serotonin
Research indicates that serotonin mediates an individual’s response to a situation, as
individuals with low serotonin have a decreased activation of the limbic system, meaning
they may have less control over their emotions leading to aggression. But when serotonin is
at normal levels it creates a calming inhibitory effect on neural firing in the prefrontal cortex
(Cases 1995), as too high or low it may disrupt the inhibited firing of neurones and people
are less able to resists aggressive urges.
Testosterone
As testosterone is linked to aggression this may explain why men are much more aggressive
than females as men produce higher concentrations (especially adolescents).
1. It effects young babies in the critical time period of a few days after birth where
sensitisation of neural circuits occurs.
2. Adulthood when testosterone modulates neurotransmitter pathways
3. It may influence areas such as amygdala and the hippocampus and serotonin
Study in support Dabbs 1987: measured salivary testosterone in violent criminals and found
those with lowest levels had committed the least violent crimes.
P neural and hormonal explanations are biologically reductionist
E explains aggression by using biological systems not through looking holistically at a person
E albert 1994 found no correlation between violence and testosterone in male prisoners
L which suggests a holistic approach should be taken as its highly unlikely there’s just one
contributing factor
, P support for amygdala and hippocampus Kulver and Bucy 1937
E removing temporal lobes (amygdala and parts of hippocampus) meant the rhesus
monkeys could see emotion but not recognise the meaning
E also supported by humans who had damaged this area
L demonstrating the importance of limbic system in controlling aggression
P neural and hormonal research is mainly conducted on animals
E Raleigh 1991 vervet monkeys fed on diets which raise serotonin levels, were less
aggressive
E can’t be generalised to humans as differences in aggression
L humans have much more complex factors contributing to aggression so generalise with
caution
SEE SZ BOOK FOR EXAMPLE 16 MARKER
Genetic factors
Genes determine how much of a hormone (testosterone) is produced and responded too.
There are a few ways to study the influences of genetics on behaviour:
1. adoption studies Mednick 1984 who found adoptees with a criminal parent 20% also
had a conviction, but those with a criminal adoptive parent only 15% had cc. But
together 25% (interactionist)
2. twin studies such as Berkowitz who found that MZ twins have an 87% concordance
rate for aggression.
MAOA gene
Regulates the MAOA enzyme to break down dopamine and serotonin, this gene removes
excess amounts of these neurotransmitters and reduces aggression. People can show
aggression due to a defective MAOA gene (MAOA-L) that can’t produce the enzyme to break
down the neurotransmitters so low levels of serotonin, high levels of adrenaline and high
dopamine which are all linked to aggression.
MAOA-L has been associated with populations with a history of warfare, but just having this
gene doesn’t automatically make you a psychopath it must be stimulated by an
environmental stimulus – diathesis stress interactionist approach
P research by Caspi to some extent supports the role of genetics in aggression
E he found having the MAOA-L gene didn’t impact aggression unless the person had been
abused as a child and was 3X more likely to impact males
E genetic factors only play a role if first stimulated by an environmental nurture effect
L taking an interactionist approach including both nature and nurture will more thoroughly
help to explain aggression
P different studies use different methods of measuring aggression
E some studies use self-report, questionnaires, observation or even ask peers
E all methods of measuring are subject to social desirability bias
L meaning individual studies lack validity but also makes them hard to compare as so many
different ways of measuring aggression so valid conclusions can’t be made
Neural and hormonal mechanisms
The limbic system lies beneath the cortex involving the amygdala and the hippocampus
mediates motivated behaviours, emotional states and memory processes.
Amygdala
Maybe part of area responsible for emotion and aggression based on research by Pardini
2014 who conducted a longitudinal study of 56 males with histories of violence, these males
had an MRI aged 26 and it showed a that smaller the amygdala the more aggressive the
criminal is.
Hippocampus
Helps to form LTMs thus allowing us to respond to current threat situations with experience
(e.g. is this person dangerous or not), misunderstanding of this sensory info will lead to the
amygdala to respond inappropriately this is supported by Adrian Raine 2004 who viewed
psychopaths under an MRI and found that they had asymmetries in the hippocampi volume
which in turn restricted communication between the hippocampi and the amygdala, which
led to inappropriate responses (aggressive behaviour).
Serotonin
Research indicates that serotonin mediates an individual’s response to a situation, as
individuals with low serotonin have a decreased activation of the limbic system, meaning
they may have less control over their emotions leading to aggression. But when serotonin is
at normal levels it creates a calming inhibitory effect on neural firing in the prefrontal cortex
(Cases 1995), as too high or low it may disrupt the inhibited firing of neurones and people
are less able to resists aggressive urges.
Testosterone
As testosterone is linked to aggression this may explain why men are much more aggressive
than females as men produce higher concentrations (especially adolescents).
1. It effects young babies in the critical time period of a few days after birth where
sensitisation of neural circuits occurs.
2. Adulthood when testosterone modulates neurotransmitter pathways
3. It may influence areas such as amygdala and the hippocampus and serotonin
Study in support Dabbs 1987: measured salivary testosterone in violent criminals and found
those with lowest levels had committed the least violent crimes.
P neural and hormonal explanations are biologically reductionist
E explains aggression by using biological systems not through looking holistically at a person
E albert 1994 found no correlation between violence and testosterone in male prisoners
L which suggests a holistic approach should be taken as its highly unlikely there’s just one
contributing factor
, P support for amygdala and hippocampus Kulver and Bucy 1937
E removing temporal lobes (amygdala and parts of hippocampus) meant the rhesus
monkeys could see emotion but not recognise the meaning
E also supported by humans who had damaged this area
L demonstrating the importance of limbic system in controlling aggression
P neural and hormonal research is mainly conducted on animals
E Raleigh 1991 vervet monkeys fed on diets which raise serotonin levels, were less
aggressive
E can’t be generalised to humans as differences in aggression
L humans have much more complex factors contributing to aggression so generalise with
caution
SEE SZ BOOK FOR EXAMPLE 16 MARKER
Genetic factors
Genes determine how much of a hormone (testosterone) is produced and responded too.
There are a few ways to study the influences of genetics on behaviour:
1. adoption studies Mednick 1984 who found adoptees with a criminal parent 20% also
had a conviction, but those with a criminal adoptive parent only 15% had cc. But
together 25% (interactionist)
2. twin studies such as Berkowitz who found that MZ twins have an 87% concordance
rate for aggression.
MAOA gene
Regulates the MAOA enzyme to break down dopamine and serotonin, this gene removes
excess amounts of these neurotransmitters and reduces aggression. People can show
aggression due to a defective MAOA gene (MAOA-L) that can’t produce the enzyme to break
down the neurotransmitters so low levels of serotonin, high levels of adrenaline and high
dopamine which are all linked to aggression.
MAOA-L has been associated with populations with a history of warfare, but just having this
gene doesn’t automatically make you a psychopath it must be stimulated by an
environmental stimulus – diathesis stress interactionist approach
P research by Caspi to some extent supports the role of genetics in aggression
E he found having the MAOA-L gene didn’t impact aggression unless the person had been
abused as a child and was 3X more likely to impact males
E genetic factors only play a role if first stimulated by an environmental nurture effect
L taking an interactionist approach including both nature and nurture will more thoroughly
help to explain aggression
P different studies use different methods of measuring aggression
E some studies use self-report, questionnaires, observation or even ask peers
E all methods of measuring are subject to social desirability bias
L meaning individual studies lack validity but also makes them hard to compare as so many
different ways of measuring aggression so valid conclusions can’t be made
