Agression

What is the limbic system

A network of subcortical structures in the brain - hypothalamus, hippocampus, thalamus, and the amygdala

What is the amygdalas role

How an organism assesses and responds to threats and challenges in the environment

The reactivity of the amygdala is believed to be a good predictor of aggressive behaviour

What is a study involving the amygdala and aggression

Gospic (2011) used a laboratory method involving 2 players. The proposer offers to split money in a certain way with the responder. If the responder accepts, then the money is split but if the responder refuses, both players receive nothing.

When participants play as the responder their brains were scanned using fMRI. When responders rejected unfair offers scans revealed a fast and heightened response by the amygdala. Therefore, showing they found increased activity of the amygdala during aggression.

What is the Orbitofrontal cortex/ OFC

Works cooperatively with the amygdala and is involved in impulse control including inhibiting aggressive responses

What is the role of serotonin

It has widespread inhibitory effects in the brain, slowing down and dampening neural activity.

Normal levels of serotonin in the OFC are linked with reduced firing of neurons and thus thought to be involved in individuals having greater ability to control behaviour, like aggression

What does decreased levels of serotonin imply?

Decreased serotonin levels may disturb the self regulation mechanism leading to reduced self-control and thus an increase in impulsive behaviour, including aggression.

What study supports the role of serotonin in aggression

Virkkunun et al (1987) took cerebrospinal fluid from violent offenders and found that they had a lower than average serotonin level.

These offenders with low serotonin levels were also more likely to commit further violent crimes after their release from prison.

What are the contradictory findings from a study into genetic explanations of aggression through serotonin

Brunner et al (1993) studied a Dutch family, many of whom were very aggressive. The aggressive behaviour was linked to a mutation on the MAO-A gene, this enzyme breaks down serotonin. The mutation caused a lack of MAO-A to break down serotonin, increasing overall serotonin levels.

Unlike previous studies this lead to increased aggression.

What is testosterone in aggression

The male sex hormone influences aggression from a young adulthood onwards due to its action on brain areas involved controlling aggression.

What study supports the role of testosterone in aggression

Dolan (2001) studied 60 male offenders in maximum security hospitals in the UK. Dolan found a positive correlation between these men’s aggression levels and testosterone levels

What is the reciprocal model of testosterone

It suggests that testosterone levels vary with the person’s dominance, therefore the level testosterone is the effect of, and not the cause of dominance.

Seen in the Mazur et al (1998) study of 2,100 air force veterans. Over a 10 year period the veterans were given 4 medical examinations. The testosterone levels reduced when they were married and increased when they divorced.

What is a neural and hormonal influences

Structures in the brain such as the limbic system, neurotransmitters such as serotonin & hormones such as testosterone

What are genetic influences of aggression

Involving looking at twin & adoption studies, specific genes and their possible involvement in aggression, such as the MAO-A gene

What is a limitation of neural/ hormonal explanations of aggression

The data is correlational. Research that identifies a link between serotonin and aggression risks oversimplifying that the true mechanisms involved especially if animal studies are involved.

What is a twin study supporting the genetic factors of aggression

Coccaro et al (1997) studied aggressive behaviours in twins and found that there was a 50% concordance rate in aggression in MZ twins and the concordance rate of 19% for DZ twins

What is an adoption study supporting the genetic factor of aggression

Hutchings et al (1975) conducted a study of over 14,000 adoptions in Denmark found that a significant number of adopted boys with criminal convictions had biological parents with criminal convictions.

What is the MAO

An enzyme and its function is to metabolise neurotransmitters after a nerve impulses has been transmitted between neurons. It breaks down the neurotransmitters into its constituent chemicals to be recycled or excreted. Production of this enzyme is controlled by the MAO-A gene

What does the MAO-A low gene do

It leads to low MOA-A activity in certain areas of the brain. This causes a failure to break down serotonin following synaptic transmission and results in a build-up of serotonin in the synaptic gap.

What is a limitation of the genetic explanation of aggression

Findings can differ considerably between different studies. Rhee and Waldman conducted a meta-analysis of 51 twin and adoption studies and found that aggressive and anti-social behaviours was largely due to genetic contributions, but this was only the case in studies that used self reports and not in those that used parent and teacher reports.

This makes it very difficult to draw valid conclusions as there are many variables that could affect the accuracy of data.

What is a strength of genetic explanation of aggression

There is pro social study support. If the low activity variant of the MAOA gene is associated with aggression then the converse could be true - high activity variant should be related to more pro social behaviour. Merlins at el (2011) found males with the high activity variant were more cooperative in lab based tasks and less aggressive.

What is the ethological explanation of aggression

It seeks to understand the innate behaviour of animals (including humans) proposes that aggression is instinctive in all species and is adaptive

What are the adaptive functions of the Ethological explanation

• It aids survival, as it can be used to protect resources like land and food

• It establishes dominance hierarchies, and these are vital to allow access to other resources, such as females

Who shows the Ethological explanation of aggression is applicable to humans

Lorenz (1966) believed it is legitimate to make direct comparisons between species, including humans, as we are governed by the same laws of natural selection. His theory of human aggression is based on his observations of non-human primates and mainly non-mammals.

What is a ritual

A series of behaviours carried out in a set order

What is ritualistic aggression

Threat displays and appeasement played a part in aggression - these ritualistic behaviours are adaptive because if every aggressive encounter ended with death, it could threaten the existence of the species

What is a Fixed Action Patten - Stephen Lea (1984)

An environmental stimulus triggers the IRM (Innate releasing mechanism) which then results in triggering the ‘release or production of a specific sequence of behaviours

What is an Innate releasing mechanism

A built in physiological process or structure

What are the features of a Fixed Action Pattern

• Sterotyped

• Universal

• Independent of Individual experience

• Ballistic

• Specific triggers

What does Stereotyped mean in a Fixed Action Pattern

Relatively unchanging sequence of behaviours

What does Universal mean in a Fixed Action Pattern

The same behaviour is found in every individual of a species

What does Independent of Individual experience in a Fixed Action Pattern

The same for every individual regardless of experience

What does Ballistic mean in a Fixed Action Pattern

Once the behaviour is triggered it follows an inevitable course and cannot be altered before it’s complete

What was Tinbergen’s (1951) study into IRM and FAPs

-Procedure - Male sticklebacks are highly territorial during mating season, when they develop a red spot on their underbelly. If they see another male in their territory a sequence of highly-stereotyped aggressive behaviours is initiated. The sign stimulus that triggers the IRM is the sight of the red spot.

- Findings - Regardless of the shape of the model, if it had a red spot the stickleback would display aggressive behaviour. But if there was no red spot there was no aggression. Tinbergen also found that these aggressive FAPs were unchanging from one encounter to another. Once triggered, the FAP always ran to completion without any further stimulus

What is a strength of the Ethological explanation of aggression

There is supporting evidence. Research by Brunner (1993) showed that the low variant of the MAOA gene was closely associated with aggressive behaviour in humans. This indicates an innate, biological cause.

What is a limitation of the Ethological explanation of aggression

There are cultural differences in aggressive behaviour. Nisbett et al found differences in aggression between white males in the southern and northern US when subjected to insults in a research situation. Nisbett concluded that this difference was caused by cultural factors, specifically the culture of honour, which is a learned norm in southern USA.

What is the assumptions of the Evolutionary explanation of aggression

The role of aggression in an individual is important for survival and reproduction. As aggressive individuals are more able to compete for food, resources and females so are more likely to reproduce

What is Parental uncertainty

Evolutionary psychologists believe that infidelity creates an issue for males because they can never be certain if they have parented a child.