Hello and welcome to the aggression unit.
Across the next 6 videos we are going to discuss biological, evolutionary and social psychological
explanations for aggressive behaviour, as well as talk about what causes aggression
in prisons.
We will also discuss if TV, and computer games are resulting in real world violence.
In this first video we are going to investigate Neural and Hormonal explanations for aggression.
Let's get started!
Neural and hormonal mechanisms in aggression there are three distinct sections I’m going
to cover in this video, and even though they are separate you will see each of the explanations
is related to the other two, so I’m going to give you basic information about each,
a research evaluation for each, but to make it easier to remember, general evaluations
that apply to all three Neural mechanisms are anything to do with
the neuron or nerve cell.
So th at can be large structures that are collections of neurons, for example the limbic
system.
Or it can be tiny chemicals that influence how neurons work in the brain, called neurotransmitters,
and the one we need to discuss in this video is serotonin.
Hormonal mechanisms are also chemical but travel in the bloodstream altering the function
of bodily processes.
In this video we need to discuss Testosterone.
Lets give a quick definition of each before going into far more detail on how they influence
aggression.
The limbic system is a collection of neural structures deep in the center of the brain.
Two regions we are particularly interested in when it comes to aggression regulation
are the amygdala and hypothalamus.
Serotonin is what is called an inhibitory neurotransmitter, and is vital for calming
aggressive impulses.
Testosterone is the male sex hormone.
Another word for a male sex hormone is an androgen.
So as you may expect it is found in greater quantities in males.
And as we tend to see greater aggression in males it might be what is responsible.
# Limbic System So we can see in this image the range of structures
that make up the limbic system.
One of the limbic systems' roles is to process emotional information, including aggression.
Even though its made up from a wide range of structures, we only need to be aware of
two, the amygdala and the hypothalamus.
The amygdala is thought to be the origin of aggressive feelings and behaviours, and we
do see increased activity in this area in aggressive participants when we measure them
with fMRI.
A nearby region is the hypothalamus and this brings together a range of emotions and is
the part of the brain responsible for triggering the fight or flight response.
Now a really important area of the brain that's not in the limbic system but is connected
to this process is the orbito frontal cortex.
As it's the cortex that means its the outside surface, or skin of the brain.
And its located at the front just behind your forehead.
Its the part of you that makes decisions, and can overrule aggressive impulses coming
from the limbic system.
If you have ever felt really angry and almost about to be aggressive, but managed to talk
yourself down and stay in control?
Well that is partly the work of the OFC.
# Limbic System - Evaluations Early research by Egger and Flynn using cats
showed that if you electrically stimulated an area of the hypothalamus cats would suddenly
be aggressive to rats placed in their cage.
They also showed that stimulating some areas of the amygdala would increase that aggressive
behaviour, but if a slightly different region of the amygdala was stimulated the cat would
be tame, showing no aggression.
So this research really does suggest that areas of the limbic system are involved in
the production of aggressive behaviour, but the relationship of the amygdala to aggression
is complex, potentially with different regions having different functions.
But of course this is cats, and you're probably thinking, well how much could this possibly
apply to humans?
Now we can't start stimulating human amygdalas under experimental procedures, but we can
look at interesting case studies.
One report by Sumer revealed extreme aggression in a 14 year old girl who also had epeleptic
fits.
The girl was given an MRI and this showed a tumor in her brain, this tumour was pressed
up against her amygdala.
So she had surgery, fortunately it was a success with the fits disappearing, as well as a return
to normal aggression levels.
Now of course this is highly suggestive that the tumour was stimulating her amygdala resulting
in the aggressive behaviour.
But of course as a case study we have to be careful, it wasn't a carefully controlled
experiment there could have been other factors that we are not aware of coursing the aggression
beyond just this tumour.
# Serotonin So moving on to the neurotransmitter associated
with aggression, Serotonin.
We need to state that's serotonin's role is inhibitory, helping to reduce neuronal activity.
Its thought that it works in the orbito frontal cortex, helping to calm aggressive impulses
that have been received from the amygdala However the serotonin deficiency hypothesis
suggests that if the levels of serotonin in the orbito frontal cortex is too low, then
the OFC isn't able to control the aggressive impulses, resulting in aggression.
We can measure the amount of serotonin in the brain by looking at the levels of 5-HIAA
in the spinal fluid, 5-HIAA is what Serotonin is broken down into, and we see lower levels
in the spines of aggressive people, which suggests these aggressive people have low
levels of serotonin in the brain.
But in the next video we are going to look at the genetic explanation, and discuss a
variation of the MAOA gene that results in problems breaking down serotonin, resulting
in too much serotonin in the brain, and these people can show aggressive behaviour.
So we can certainly say the role serotonin has in regulating aggression is, well complex
and not fully understood.
Serotonin - Evaluations Now a cleverly designed study is by Passamonti.
We need a compound called tryptophan for our bodies to synthesize serotonin.
So passamonti asked one group of participants to cut out foods with tryptophan from their
diets.
The other group ate normally.
This tryptophan deprivation had the result of lowering serotonin in the brains of the
experimental group.
The researchers then used FMRI to see how the brain would respond to seeing angry faces.
The results showed reduced communication between the OFC and Amygdala in the frontal cortex
when participants were deprived of serotonin , suggesting that the OFC is not able to regulate
aggression in the amygdala when deprived of serotonin
# Testosterone And finally the Androgen Testosterone.
As the male sex hormone its genrally found in levels 8 times higher in males than females.
Its whats responsible for the development of sex charciteristics typcial of males.
So muscle development, body hair, that kind of thing.
But psychologists are of course much more interested in behavioral changes as a result
of increased testosterone.
And one of the biggest behavioural differences between males and females is males show much
higher levels of physical aggression.
We can see evidence for this with the much larger number of males convicted of violent
offences.
How this is thought to work is that excessive amounts of testosterone in the OFC reduces
its ability to regulate the aggression coming from the limbic system.
With reduced executive function, the individual is more prone to emotional aggressive outbursts.
It's also thought high levels in the amygdala increases its activity, producing more aggression.
And it's also thought that there is an interaction between testosterone and serotonin, with high
levels of testosterone reducing serotonin's ability to calm aggressive thoughts.
Testosterone - Evaluations An experiment by Wagner used mice, when observing
mice Wagner recorded males as more likely to aggressively bite than females.
Wagner castrated the mice, which is removing the testicles, resulting in a large drop in
testosterone production.
After castration aggression levels in the males was the same as in the females.
Then Wagner injected the mice with testosterone, increasing the biting behaviour of the males
back to the previous level, and when the females were injected they became more aggressive.
This experimental data is highly suggestive that the hormone testosterone does cause aggressive
behaviour, at least in mice.
General Evaluations I think its best if we finish with a set of
evaluations that we can reword depending on the question, so if you are directly asked
to write an essay just on one process or all three.
Everything we have covered in this video is a biological explanation for aggression.
saying, aggression is purely biological, well we might feel this argument is a little too
biologically reductionist.
Don't get me wrong, reductionism is good in some ways, a simple explanation is more open
to scientific testing and can lead to effective treatments.
But there are other persuasive social psychological explanations for aggression that we will cover
in the next few videos.
Perhaps a full explanation for aggression is more holistic, some people may be more
biologically prone to aggression than others, but this isnt expressed unless they have other
psychological experiences in their life.
Now i'm showing examples of both reductionism and determinism evaluations here, honestly
I recommend you don't use them both as often students get them mixed up and there are lots
of other evaluations you can use.
But I know about the confusion with these two so I’m using both here so you can see
the difference between them when they are next to each other.
Taking a biologically deterministic approach to aggression is suggesting that someone couldn't
act otherwise, that their biology is their destiny.
Well that's a problem when talking about aggression, which is of course linked to violent crime,
are people destined to be violent criminals?
If someone is a violent criminal, and convicted of a serious assalut or murder, what if they
have very high levels of testosterone, very low levels of serotonin, or a limbic abnormality,
sould we reduce their sentence?
Or even let them go as long as they receive treatment?
After all, they can't control any of these biological problems.
So as you can see taking a biologically deterministic approach to aggression has some seriously
problematic implications when applied in the real world.
Kind of a linked point is social sensitivity, this is the idea that the research we conduct
on people could negatively affect their lives and people like them.
If we find biological abnormalities in the limbic system are predictive of later violent
crime, this could lead to arguments of intervention before these people commit an offence.
This may seem extreme but is a debate some prominent psychologists such as Adiran Raine
are considering.
But if this happens, will this just lead to another form of descrimination against people
who have yet to commit an offence?
And a final point.
The studies we have looked at have all used carefully controlled biological measuring
tools like FMRI as careful measurements of biological chemicals like serotonin and testosterone.
This biological approach minimises much of the potential bias we see in other forms of
psychology.
So we can suggest that these studies have high internal validity, they tend to measure
what they intend to measure precisely.
These four evaluations can all actually be used as evaluations for the topic of the next
video, genetic factors in aggression.
I’m not going to repeat them there, but I would suggest after watching that video,
come back to this and think about how you could reword these points in an essay on genetic
factors.
This is a really valuable skill in your psychology A-level, and just understanding these concepts,
and knowing how to use evaluations like these effectively, adapting them to the essay you
need to write, massively reduces the number
of evaluations you have to memorise.