Biological explanations of aggression Explanation One: Brain Functioning

What causes aggressive behaviour? https://www.youtube.com/watch?v=FSoLoYOZ_7k Nature vs Nurture?

Essentially the argument is ……Brain abnormalities…… ..... are associated with aggression

Structure is how something is set up. (its parts) Function is what something is for. (its role) Task One: On the worksheet provided describe the function of each brain structure.

Which other brain structures are involved in aggressive behaviour? Rat lesion studies suggest that different types of aggression may be controlled by different subsets of brain structures. Limbic sites: (amygdala, septum and hypothalamus)

Amygdala Rabies is caused by a virus that damages the temporal lobe. Rabid animals are violently aggressive. Autopsies of Charles Whitman who carried out a sniper attack from the University Tower at Texas in 1966, showed he had a tumour pressing on his amygdala. He left a note begging for his brain to be studied. http://www.learner.org/resources/series142.html?pop=yes&pid=1593

The Role of the Amygdala Kluver-Bucy syndrome – taming effect found in rhesus monkeys by removing part of the temporal lobes and therefore destroying the amygdala. Narabyashi et al (1972) – 43 / 51 patients whose amygdala was destroyed through psychosurgery showed reduced aggression afterwards.

Mark & Ervin (1970) – case study of female patient behaviour following electrical stimulation of amygdala. She exhibited facial grimacing, became very angry and flung herself at the wall. Ashford (1980) – temporal lobe epileptics often become aggressive, attacking furniture and people.

Wong et al (1997) – criminals with violent tendencies have reduced size amygdala Van Elst et al (2000) aggressive patients with temporal lobe epilepsy, amygdala had lost 20% of its volume. The exact role of the amygdala in aggression is unclear, but it is certainly a significant one. Research suggests an interaction between the amygdala and the pre-frontal cortex.

The Role of the Prefrontal Cortex Regulates the emotional responses driven by the amygdala. Damage to prefrontal cortex results in impulsivity, immaturity and loss of control. Anderson et al (1999) – damage during infancy related to aggressive behaviour as adults. Case studies comparing early onset damage with adult onset damage to frontal lobes. Early onset patients also performed poorly on tests of moral and pro-social reasoning.

Raine et al (1997) – investigated brain activity of 41 murderers using PET scans. Found reduced glucose metabolism in prefrontal cortex, suggesting this brain area is less active than in normal controls. Volkow et al (1995) found violent psychiatric patients had reduced cerebral blood flow to prefrontal cortex. http://www.youtube.com/watch?v=_0aNILW6ILk&feature=related During the 1940s, frontal lobe lobotomies were performed with startling regularity ; partly because of the ‘calming’ effect on patients with a range of mental health problems – from depression to ADHD to OCD.

Raine et al (1997) Brain abnormalities in murderers by positron emission tomograpghy Raine et al., (2000) found that the (prefrontal cortex, which inhibits aggressive behaviour), was 14% less active than normal in non-abused murderers &15% smaller in antisocial males. THIS IS YOUR CLASSIC STUDY

Evidence: Phineas Gage Railroad Accident – Sept. 1848 Leveling land with Dynamite 3 foot inch thick tamping rod was projected in to his brain Entered via cheek, left Eye and into the frontal lobes Driven by other workers in a ox- cart to Doctor’s office The rod damaged the pre-frontal cortex. This region is implicated in personality changes and aggression/violence.

What happened? Lost conscious and had convulsion immediately, but awoke quickly and was talking and walking soon afterwards Never showed any impairment of movement or speech Memory was intact, and was capable of learning new things However, within months his personality had changed dramatically He became extravagant and anti-social, a foul mouth liar with bad manners, frequently got into fights and assaults. could no longer hold a job or plan his future According to friends “Gage was no longer Gage”, he died 13 years later A penniless, epileptic

Strengths and Weaknesses

Issues and Debates The exam requires you to develop an appreciation of issues and debates in psychology that are relevant to the particular topic. On the next slide place a tick by the relevant issues and debates that link to this topic on agression

Reductionism in Psychology Reductionism is a scientific approach that tries to explain phenomena in terms of basic elements. Brain function as an explanation of aggression is reductionist because A strength of a reductionist explanation of aggression is… A Weakness of a reductionist explanation of aggression is….

Use of animals in research Research investigating aggression and the brain involves many ethical issues when animals are used. For example….. Furthermore, the use of animals to investigate aggressive behaviour has problems of generalisability because…. However,

Social Control What is social control? How can science be used a social control?

Social Control The implications of the research into brain structure and function on aggression suggest that nature may have a role to play in aggression. Therefore suggesting that people with smaller amygdala’s are destined to be aggressive as this was how they were made. Implication of this? On the other hand, the research does not suggest causality. We can not conclude that the structural differences in the brain are the cause of the violent behaviour as they may be the……

To conclude…. 1. Describe a brain area as an explanation of aggression (3) 2. Describe aggression using the role of brain function (3) 3. Give two pieces of evidence that show that the structure of the brain is involved in aggression (4)