Neural Influences

What type of explanation is Neural

Biological

What are the two components of the Limbic system

1. The anygdala

2. The hippocampus

What does the amygdala help us do

Quickly evaluate the emotional importance of sensory information and then respond appropriate

Kluver and Bucy

A monkey that was dominate in a social group had its amygdala and so the monkey lots its place of dominance in the group

What happens to animals who have had their amygdala surgically removed

The stimulus that would result in aggression no longer results in aggression

What does the Hippocampus allow us to do

Form LTMs. This means animals can compare current threats with past experiences and respond appropriately with either aggression or fear

Boccardi

Violent offenders had abnormal hippocampus functioning

What happens when the function of the Hippocampus is impaired

The nervous system struggles to understand things in a relevant context meaning the amygdala may respond inappropriately to stimuli resulting in aggressive behaviour

What is Serotonin

A neurotransmitter associated with behaviours such as aggression, sleep and depression

What do normal levels of serotonin help

Inhibit activity of the amygdala and so reduces aggression

What happens when levels of serotonin are low

The inhibitory factor is removed making it harder to control aggressive behaviour

Research support - Evidence for the role of the amygdala in aggression

Pardini (2014): reduced amygdala volume can indicate development of severe and persistent aggression.

Longitudinal study on 56 male pps from childhood to adulthood. At age 26, some pps who had a history of violence had a brain MRI scan.

Findings: pps with lower amygdala volumes showed higher levels of aggression and violence. THEREFORE, the amygdala is key in evaluating the emotional importance of sensory information. Lower amygdala volume compromises this ability and increases the likelihood is a violent response.

There this shows that the amygdala is important 

Ethical and non-invasive 

However this is Not a representative sample size 

Research support for the role of the hippocampus in aggression

Raine at al (2004) studied 2 groups of violent criminals:

Group 1 = ‘unsuccessful psychopaths’ (been caught and convicted).

Group 2 = ‘successful psychopaths’ (evaded the law).

Group 1 acted more impulsively, hence being caught.

Group 2 were seen as ‘cold, calculating’ criminals.

Group 1's MRI scans showed an asymmetrical hippocampus (different sizes in each hemisphere).

THEREFORE, this asymmetry might prevent the hippocampus and amygdala from working together, and so emotional information isn’t processed accurately - thus resulting in inappropriate responses (physical/verbal).

Evidence from non-human species

Raleigh et al. (1991): monkey’s who fed on experimental diets that are high in tryptophan (increases serotonin levels) - showed less aggression, and vice versa.

Rosado et al (2010): 80 dogs (various breeds) referred to Spanish vets because of their aggressive behaviour towards humans. They were compared to 19 dogs (various breeds) that didn’t show this aggressive behaviour.

Aggressive dogs = 278 units of serotonin.

Non-aggressive dogs = 387 unit of serotonin.

(estimate) 

THEREFORE, different levels of aggression can be attributed to animals’ serotonin levels.