Biological influences on aggression

Question 1

Neural and hormonal

Neural influence

Answer 1

Certain areas of the brain play a key role in aggressive behaviour
- the limbic system and the amygdala
- the prefrontal cortex

Question 2

Neural influence

Limbic system

Answer 2

The limbic system is part of the ‘old brain’ that we share with other animals.

It is also the brain’s emotion centre where our most basic urges (appetite, sleep, sex drive, fear) are regulated.

Question 3

Neural influence

The amygdala

Answer 3

The amygdala is strongly associated with fear and aggression. It takes interpretated information as a threat or not.

Question 4

Neural influence

Pre-frontal cortex

Answer 4

• responsible for planning, reasoning and more specifically, in relation to agression, impulse control and personality.

Question 5

Pre-frontal damage

Phineas Gage

Answer 5

Cases such as Phineas Gage have shown patients with damage to this part of the brain become irritable, with inappropriate outbursts of anger and are more likley to respond aggressively in conflict situations.

Question 6

Neural and hormonal

Hormonal influence

Answer 6

Typically, hormones are released by a gland and travels around the bloodstream, affecting organs or other parts of the body.

Question 7

Neural and hormonal

Neurotransmitters

Answer 7

• a chemical released by neurons which carry information from one neuron to another

Question 8

Neurotransmitters

Serotonin

Answer 8

A neurotransmitter linked to mood and sadness.
- makes us feel happy so treatment for depression often involves medicines that boost serotonin levels in the brain

Question 9

Neurotransmitters

Low levels of serotonin

Answer 9

Low levels of serotonin are also associated with increased aggression. This is because serotonin seems to inhibit aggression so if you have low serotonin levels, you are more likely to act aggressively.

Question 10

Serotonin Study

Answer 10

A rat study by Popova et al in 1991 found that rats selected for reduced aggression levels had higher serotonin levels than wild, more aggressive counterparts.

Question 11

Hormonal influence

Testosterone

Answer 11

It is particulary associated with male sexual development - its levels greatly increase in boys when they approach puberty.

Testosterone is strongly associated with competition and aggression. Higher levels of testosterone is associated with increased fighting in many species.

Question 12

Hormonal influence

Testosterone - Challenge hypothesis

Answer 12

suggets that the hormone’s main function is to help species seek and fight for mates, fight challengers and keep mates that they have already paired up with (mate guarding)

Question 13

Testosterone research

Wagner et al (1979)

Answer 13

Over 19 sessions, it was discovered that the mouses aggression varied a lot, but after castration it clearly drops. When mice are injected with 150 micrograms of testosterone a day, their aggression creeps back up to the old levels.

Question 14

Testosterone research

Mazur and Booth (1993)

Answer 14

Men with higher levels of testosterone are most likely to:
- divorce, or remain single
- be arrested (for offences other than traffic violations)
- to buy and sell stolen property
- use a weapon in fights

Question 15

Genetics

Selective breeding

Answer 15

The role of genetics and selective breeding is most easily explained through canine behaviour. For centuries, dog breeders have selected particular traits by simply watching how a dog behaves. They have bred dogs for specific tasks by removing the dogs that perform less well from their breeding stock.

Question 16

Genetics

Human aggression

Answer 16

A general principle of the evolutionary approach is that behaviours have evolved to serve a purpose that aids survival or reproduction.

It is of great social importance to know why people become mass murderers while others to go through life engaging in little or no aggression at all.

Question 17

Genetics

MAO

Answer 17

MAO, or monamine oxidose, exists in each neuron in the brain, and it acts like a recycling factor for neutransmitters. In people who have the ‘warrior gene’, less MAO is produced, which means that less of the neurotransmitters serotonin, norepinephrine and dopamine are broken down.

Higher levels of these brain chemicals see to equal higher levels of aggression. These people feel less empathy for others, and are more willing to harm others on a whim.

Question 18

Genetics

MAOA - the warrior gene

Answer 18

MAOA is regulated by the MAOA gene and humans have various forms of the gene, resulting in different levels of activity of the enzyme.

One variant of the gene is associated with high levels of MAOA (MAOA-H) and another variant is associated with low levels (MAOA-L). Several studies have now found a correlation between low-activity from the MAOA gene and aggression

Question 19

Genetics

MAOA research

Answer 19

A study by Caspi et al (2002) looked at the role of MAOA-L in boys who had suffered abuse. They wanted to know why some men who have suffered abuse in their childhood grow up to be antisocial and violent while other do not. They believed that deficient MAOA activity caused by the MAOA-L version of the gene may lead to a person being hyper-reactive to threats, and this could be particularly problematic in early childhoods when resilience to threats has not fully developed.

Question 20

Genetics

MAOA research - findings

Answer 20

They found that the presence of the gene interacted with child abuse, Of the men in the study who had experienced abusive childhoods, around 12% had the MAOA-L gene, but these participants were responsible for half of the convictions for violent crimes among the sample. This supports the idea that some people are gentically more predisposed to aggression but that adverse life events play a role too.

Question 21

Genetics

MAOA - The warrior gene

Evidence

Answer 21

McDermott (2009) conducted an experiment in which she asked participants to cause physical pain to those they had believed had taken money from them by giving them various amounts of hot sauce. The resuts found that those with the MAOA gene were much more likely to administer higher levels of hot sauce.

Question 22

Genetics

Twin Studies

Answer 22

In determining if a trait in a human’s behaviour is related to genetic factors or environmental factors twin studies are used. These studies examine correlations based on similarities of a trait and a person’s genetic factor that may be influencing the trait.

Research with human studies has focused on twin studies that have looked at the incidence if aggression displayed by monozygotic (identical) and by dizygotic (non-identical) twins.

Question 23

Genetics

Epigenetics

Answer 23

Genes and environment interact biologically, and genes can be switched on or off depending on life experiences and the environment.

Question 24

Evolutionary

Answer 24

Aggression is seen in all animal species and is believed to be an innate behaviour. If behaviours is innate, evolutionary psychologists propose that the behaviour must be beneficial to the organism. Aggression as a behaviour can help survival, as aggression can protect resources such as land and food. Aggression establishes dominance hierarchies, and these are vital to allow access to resources

Question 25

Evolutionary

Natural Selection

Answer 25

Natural Selection assumes that animals with the most successful traits for reproduction and survival will pass their genes on to offspring.

Question 26

Evolutionary

Buss and Shachelford (1997)
Securing resources

Answer 26

Humans stockpile resources which are important for survival and reproduction

Question 27

Evolutionary

Buss and Shachelford (1997)
Establishing status

Answer 27

Aggressions can enhance ones personal status within a group. In Western cultures aggression has been ritualised within sporting contexts and top performers can achieve very high status.

Question 28

Evolutionary

Buss and Shachelford (1997)
Deterring attack

Answer 28

The presence of individuals who may attack you prompts groups or individuals to use aggression as a means of preventing ones resources from being taken.

Question 29

Evolutionary

Buss and Shachelford (1997)
Sexual competition

Answer 29

Aggression or the threat of aggression may deter parent partners from sexual infidelity. There is much evidence to suggest that mate sexual jealousy is a key factor in spouse abuse.

Question 30

Evolutionary

Evaluation of Buss
Gender and Ethics

Answer 30

Critics feel this theory could be used to justify violence against women

Question 31

Evolutionary

Evaluation of Buss
Deterministic

Answer 31

Buss himself always points out that we are not controlled by our genes; we have inherited the ability to learn and to choose

Question 32

Evolutionary

Evaluation of Buss
Reductionist

Answer 32

Is this an over-simplification? Are there other issues which promote aggression such as culture or individual differences in testosterone

Question 33

Ethological

Answer 33

Ethology places more emphasises on the natural habitat It recognises that while behaviours have evolved and are caused by genes, most species also adapt to environmental circumstances and learn from experience.

Question 34

Ethological

Two concept of ethology

Answer 34

A fixed action pattern - this is similar to an ‘instinct’, but ethologists are interested in how these actions can respond to circumstances and adapt to specific environemntal contexts

A releaser (or releasing mechanism) - this is a social action pattern

Question 35

Ethological

How does Lorenz view aggression?

Answer 35

According to Lorenz, aggression builds up like a drive within the animal until it is released, in this way; the need to be aggressive is much like other psychological needs such as food, water and sex.

Question 36

Ethological

Lorenz

Answer 36

The innate releasing mechanism is a set of inherited neural circuits in the brain that attempts to prevent the release of the aggression drive until there are cues in the environment. This is hardwired and part of the animal’s biology when born. Lorenz also suggested that most animals have innate releasers which bring an end to a fight.

Question 37

Ethological

Lorenz - in relations with humans

Answer 37

Lorenz states that humans may have lost their releasers which leads to violence that doesn’t stop. It also argued that the long distance nature of violene with weapons means that we don’t get visual or auditory feedback about a victims suffering - cues which might put a stop to violence among other animals.

Question 38

Ethological

Tinbergen (1952)

Answer 38

He was interested in how animals establish a territory, and show aggression when this is invaded by other individuals. His classic study of stickleback fish demonstrated how fixed action patterns relating to mating and aggression are promoted by releasers which experimenters were able to mimic.

Question 39

Ethological

Tinbergen (1952)
Results

Answer 39

All males attacked only the unrealistic wooden models with the red bellies. This shows that the red patches act as a biological trigger to start an aggressive fixed action pattern, even when there was no threat.

Question 40

Raine et al (1997)
Study of brain abnormalities in murderers

Aim

Answer 40

The study aimed to find out the role played by brain areas including the prefrontal cortex, the corpus callosum and the amygdala in predisposing people towards people who had controlled violent crimes.

Question 41

Raine et al (1997)
Study of brain abnormalities in murderers

Method

Answer 41

This was a quasi-experiment. The experiment is considered quasi because the experimenters could not manipulate the independent variable as it was naturally occurring: a person was a murderer, or they were not a murderer.

Question 42

Raine et al (1997)

Method - IV and DV

Answer 42

The IV was “whether the participant was a ‘normal’ non-murderer or a murderer who had plea ‘not-guilty by reason of insanity.’”

The DV was whether the participant showed evidence of brain dysfunction in their prefrontal cortex and other areas such as the amygdala and corpus callosum.

Question 43

Raine et al (1997)
Study of brain abnomalities in murderers

Participants

Answer 43

41 participants (39 male, 2 female) who had been charged with murder and had pled not guilty on the grounds of insanity, the precise reasons varied from schizophrenia to head injuries. As part of their defense, the prisoners received brain imaging scans and Raine took the opportunity to compare the prisoners scans with a group of controls.

Question 44

Raine et al (1997)
Study of brain abnormalities in murderers

Findings

Answer 44

Brain scans from these participants were compared with a control group of 41 participants with no convictions.

As expected, the scans showed less activity in the frontal lobe, especially the prefrontal cortex, which is associated with rational thinking and self-restraint. There was also less activity in the parietal lobe, which is associated with abstract thinking.

There was an imbalance of activity between the left and right hemispheres in the limbic system. There was less activity on the left and more on the right in the amygdala and on the right side of the thalamus.