Section D: Aggression

Question 1

What are 2 types of aggression?

Answer 1

1. Proactive aggression: ‘cold-blooded’, planned method of getting something.
2. Reactive aggression ‘hot-blooded’, angry and impulsive.

Question 2

Name 2 neural mechanisms in aggression.

Answer 2

• The Limbic system

- Serotonin.

Question 3

What is the limbic system? Name its 2 key structures.

Answer 3

Central area of the brain that helps coordinate behaviours.

Amygdala and Hippocampus

Question 4

What is the Amygdala?

Answer 4

Responsible for evaluating the emotional importance of sensory information and producing an appropriate response. If the amygdala is more reactive the level of aggressiveness increases.

Question 5

Amygdala- what did Kluver and Busy discovered?

Answer 5

The reactivity of the amygdala in humans have proven to be an important prediction of aggressive behaviour.

Question 6

Evidence to support - Amygdala (Pardini et al: 2014)

Answer 6

He found that reduced amygdala volume could predict the development of severe and persistent aggression.

He carried out a longitudinal study of male participants from childhood to adulthood. 56 of the participants with varying histories of violence were subjected to a brain MRI at age 26. The results showed that participants with lower amygdala volumes exhibited higher levels of aggression and violence. ​

This suggests that the amygdala plays an important role in evaluating the emotional importance of sensory information and that lower amygdala volume compromises this ability and makes a violent response more likely. ​

Question 7

What is the hippocampus?

Answer 7

This is involved in the formation of long-term memories, and so allows an animal to compare the conditions of the current threat with similar past experiences.

i.e. if an animal had previously been attacked by another animal, the next time they encounter that animal they are likely to respond either with aggression or fear.

Question 8

What happens if someone has an impaired hippocampal function?

Answer 8

It prevents the nervous system from putting things into a relevant and meaningful context, and so may cause the amygdala to respond inappropriately to sensory stimuli, resulting in aggressive behaviour.

Question 9

Evidence to support - hippocampus (Raine et al: 2004)

Answer 9

Conducted the study of violent offenders. ​

They studied two groups of violent criminals: some who had faced conviction (‘unsuccessful psychopaths’) and some who invaded the law (‘successful psychopaths’). The latter group were considered to be ‘cold, calculating’ criminals, whereas the former group had acted more impulsively, which is why they were caught. MRI scans revealed asymmetries in the hippocampus in the ‘unsuccessful’ group. The hippocampus in either hemisphere of the brain in these individuals differed in size, an imbalance presumed to have arisen early in their brain development. ​

The researchers suggested this asymmetry might impair the ability if the hippocampus and the amygdala to work together, so that emotional information is not processed correctly, leading to inappropriate verbal and physical responses. ​

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Question 10

What is a neurotransmitter?

Answer 10

Chemicals that allow impulses to be transmitted throughout our brain and body. ​

Question 11

Serotonin in normal levels.

Answer 11

It exerts a calming, inhibitory effect on neuronal firing in the brain.
Typically inhibits the firing of the amygdala, the part of the brain that controls fear, anger and other emotional responses. ​

Question 12

Low level of serotonin.

Answer 12

It removes this inhibitory effect, making individuals less able to control impulsive and aggressive behaviour (the serotonin deficiency hypotheses).
As a result, when the amygdala is stimulated by external events, it becomes more active.

Question 13

How does serotonin reduce aggression?

Answer 13

By inhibiting responses to emotional stimuli that might otherwise lead to an aggressive response.
Some drugs are thought to alter serotonin levels and thus increase aggressive behaviour. ​

Question 14

Evidence - serotonin (Mann et al. (1990))

Answer 14

He gave 35 healthy participants dexfenfluramine, which is known to deplete serotonin. Using a questionnaire to access hostility and aggression levels, they found that dexfenfluramine treatment in males (but not females) was associated with an increase in hostility and aggression scores. ​

Question 15

Evaluation - research support for the serotonin deficiency hypothesis (Duke et al - 2013)

Answer 15

He carried out a meta-analysis of 175 studies, involving 6500 participants. A small inverse relationship between serotonin levels and aggression, anger and hostility was found. They level of the relationship varied with the methods used to assess serotonin functioning, with year of publication and with self-reported versus other- reported aggression. Only other-reported aggression was positively correlated to serotonin functioning. ​

This suggests that the relationship between serotonin and aggression is more complex than originally thought. ​

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Question 16

Evaluation - evidence from studies of non-human species. (Raleigh et al - 2010)

Answer 16

He found that vervet monkeys fed on experimental diets high in tryptophan (which increases serotonin levels in the brain) exhibited decreased levels of aggression. Individuals fed on diets that were low in tryptophan exhibited increased levels of aggressive behaviour.

This supports the idea that when there’s low levels of serotonin, aggression increases.

Question 17

Evaluation - evidence from studies of non-human species. (Rosado et al - 2010)

Answer 17

He compared a sample of 80 dogs of various breeds that had been referred to Spanish veterinary hospitals for aggressive behaviour towards humans with a control sample of 19 dogs of various breeds. The aggressive dogs averaged 278 units of serotonin, while the non-aggressive dogs averaged 387 units. ​

This supports the idea that when there’s low levels of serotonin, aggression increases.

Question 18

Name a hormonal mechanism in aggression.

Answer 18

Testosterone

Question 19

What is testosterone?

Answer 19

It produces male characteristics, one of which is aggressive behaviour. Levels reach a peak in young males, and then decline.

Question 20

Evidence to support - Testosterone: Saplosky (1998)

Answer 20

He summarised research evidence in this area by describing how removing the source of testosterone in different species typically resulted in much lower levels of aggression. Subsequently reinstating normal testosterone levels with injections of synthetic testosterone led to the return of aggressive behaviour. ​
e.g.

Men are generally more aggressive than women (Archer, 2009) ​

Have much higher concentrations of testosterone than women (Dabbs, 1990).​

In addition, at an age when testosterone concentrations are at their highest (21-35), there is an increase in male-on-male aggressive behaviour (Daly and Wilson, 1998). ​

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Question 21

Evidence to support - Testosterone: Dabbs et al (1987)

Answer 21

He measured salivary testosterone in violent and non-violent criminals. Those with the highest concentrations of testosterone levels had a history of primarily violent crimes. whereas those with lowest levels had committed only non-violent crimes. ​

Question 22

Evidence to support - Testosterone: Carre and Olmstead

Answer 22

He claimed that testosterone concentrations are not static, but fluctuate rapidly in the context of changes to the social environment. Changes in testosterone levels appear to influence aggressive behaviour by increasing amygdala reactivity during the processing of social threat (e.g. angry facial expressions). ​

Question 23

Evaluation of hormonal mechanisms in aggression: Testosterone
2 limitations

Answer 23

• Inconsistent evidence: Albert et al (1994)
• Justin Carre and Pranjal Mehta’s (2011) dual-hormone hypothesis attempts to explain why. They claim that high levels of testosterone lead to aggressive behaviour only when levels of cortisol are low. When cortisol is high, testosterone’s influence on aggression is blocked. Cortisol is a glucocorticoid hormone that plays a central role in the stress response. ​

Question 24

Evaluation for both neural and hormonal mechanisms of aggression​.

Answer 24

Most research uses correlational techniques.
There are good ethical and practical reasons for this because; opportunities to experimentally manipulate brain structures and hormones are limited.

Question 25

How are genetic factors studied in aggression?

Answer 25

Twin studies, Adoption studies and using techniques for investigating the important role of the MAOA gene.

Question 26

What have twin studies suggested about aggression?

Answer 26

Heritability accounts for about 50% of the variance in aggressive behaviour.

Question 27

Explain Emil Coccaro et al’s research on aggression

Answer 27

He studied adult male MZ and DZ twins. Because MZ twins share 100% of their genes but DZ twins share, only 50% we would expect to find greater similarities in aggressive behaviour between MZ twins (if aggression is mostly influenced by genetic factors).

For aggressive behaviour (defined as direct physical assault), the researchers found concordance rates of 50% for MZ twins and 19% for DZ twins. The corresponding figures for verbal aggression were 28% for MZ twins and 7% for DZ twins.​

Question 28

Evaluation of Emil Coccaro’s research.

MZ rate not 100%

Answer 28

For psychologists to be able to state conclusively that aggression is genetic the concordance rate would have to be 100% (inheritability co-efficient of 1.0) for MZ twins as these twins share the same genetic make-up. ​

As it is not 100%, it suggests that there are other contributing factors such as social, environmental or psychological that are responsible for the development of aggression.​

Question 29

What do adoptions studies suggest about aggression?

Answer 29

If there are similarities in aggressive behaviour between an adopted child and their biological parents it suggests that genetic influences are operating when and if there are similarities with the adopted parents with regard to aggressive behaviour, then this suggests that environmental influence are also operating.

Question 30

Example of adoption studies: Hatchings and Mednick (1975)

Answer 30

They carried out a study of over 14,000 adoptions in Denmark and found that a significant number of adopted boys with criminal convictions had biological parents (particularly fathers) with convictions for criminal violence, providing evidence for the genetic effect. ​

Question 31

Example of adoption studies: Soo Rhee and Irwin Waldman (2002)

Answer 31

They carried out a meta-analysis of 51 adoption studies of direct aggression and antisocial behaviour. They found that genetic influences accounted for 41% of the variance in aggression, which is similar to the findings from twin studies.

Question 32

Evaluation of Adoption studies.

Reliability of measuring aggression

Answer 32

Methods of measuring aggression differ significantly between studies, and include self-reports, parent and teacher reports, and direct observations. ​

In Rhee and Waldman’s meta-analysis of 51 twin and adoption studies, genetic factors had a greater influence on aggression in studies using self-reports rather than parent or teacher reports. ​

If research findings vary depending upon how aggression is measured, then it becomes very difficult to draw valid conclusions about the role of genetic factors.​

Question 33

What is the MAOA gene and what is its function?

Answer 33

Monoamine oxidase A (MAOA) is an enzyme. Its role is to ‘mop up’ neurotransmitters in the brain after a nerve impulse has been transmitted from one neuron to another. It does this by breaking down the neurotransmitter, especially serotonin, into constituent chemicals to be recycled or excreted (catabolism). ​

The MAOA gene determines the production of this enzyme. A dysfunction in the operation of this gene may lead to abnormal activity of the MAOA enzyme, which in turn affects levels of serotonin in the brain.​

Question 34

What is the warrior gene?

Answer 34

A variant of the MAOA gene that leads to low MAOA activity in areas of the brain, and has been associated with various forms of aggressive behaviour. ​

Question 35

Research Example - warrior gene

Han Brunner et al. (1993)

Answer 35

He studied 28 male members of a large Dutch family who were repeatedly involved in impulsively aggressive violent criminal behaviours such as rape, attempted murder and physical assault. The researchers found that these men had abnormally low levels of MAOA (warrior gene) in their brains and the low activity version of the MAOA gene.

Question 36

Evaluation of geneteic factors in aggression.

Caspri et al (2002)

Answer 36

He studied 500 male children and discovered a variant of the gene associated with high levels of MAOA (MAOA-H) and a variant associated with low levels of MAOA (MAOA-L). ​

Those with MAOA-L variant were significantly more likely to grow up to exhibit anti-social behaviour but only if they had been maltreated as children. ​

Children with MAOA-H variant who were maltreated, and those with MAOA-L who were not maltreated did not display antisocial behaviour. ​

Question 37

Evaluation of geneteic factors in aggression.

2 limitations

Answer 37

• Problems of sampling.

- Difficulties determining the role of genetic factors.

Question 38

What is ethology?

Answer 38

Study of animal behaviour in natural settings.

Question 39

Who is the founder of ethology and how does he define aggression?

Answer 39

Konard Lorenz (1966)

The finghting instinct in beast and man which is directed against a member of the same species.

Question 40

What is aggression from the POV of ethology?

Answer 40

An instinct, it occurs in all members of a species without the need for learning: it is innate and mostly genetically determined.​

Question 41

What is the adaptive function of aggression?

Answer 41

Aggression is beneficial to survival because a ‘defeated’ animal is usually forced to establish territory elsewhere. This means that members of a species are spread over a wider area and have to discover resources in a different place, which reduces competition pressure and the possibility of starvation.​

Another adaptive function of aggression is to establish dominance hierarchies.

Question 42

Research example - Adaptative function of aggression

Gregory Pettit et al (1988)

Answer 42

He studied playgroups of young human children and observed how aggression played an important role in the development of some children’s dominance over others. This would be adaptive (and thus naturally selected) because dominance over others brings benefits such as power to get your own way and access to resources.

Question 43

What is ritualistic aggression?

Answer 43

A ritual is a series of behaviours carried out in a set order. One of Lorenz’s early observations of fights between animals of the same species was how little physical damage was done. Most aggressive encounters consisted mainly of a period of ritualistic signally (e.g. displaying claws and teeth, facial expressions of threat) and it rarely reached the point of becoming physical.

Question 44

Evaluation of adaptive function of aggression + ritualistic aggression.
2 strengths

Answer 44

• In the non-human species, the main advantage of ritualised aggression is that it prevents conflicts escalating into potentially dangerous physical aggression. ​

Anthropological evidence suggests that this advantage is also evident in human cultures, e.g. Chagnon (1992)

• The view that aggression has evolved into self-limiting and relatively physically harmless ritual has been questioned. ​ e.g. Goodall (2010)

Question 45

Evaluation of adaptive function of aggression + ritualistic aggression.
Extrapolation issues

Answer 45

Lorenz did not study higher mammals such as primates. However, he made generalisations about aggressive behaviour in humans. Humans are seen as much more complex than animals and this reduces the validity of this explanation. When studies were conducted on higher mammals (Goodall, 2010) that are seen to be more like humans, the ethological explanation was not supported. ​

Question 46

What are FAPs (fixed action patterns)?

Answer 46

The ethological explanation states that all members of the same species (conspecifics) have a repertoire of innate stereotyped behaviours which occur in specific conditions and which do not require learning.

Question 47

Outline 5 features of FAPs.

Answer 47

Stereotyped- the behaviour always occurs in the same way​

Universal - the same behaviour is found in every individual of a species.​

Independent of individual experience- the behaviour is innate with no learning involved.​

‘Ballistic’- once triggered, the FAP cannot be changed for stopped.​

Specific triggers- each FAP has a specific trigger (sign stimulus) ​

Question 48

How are FAPs produced?

Answer 48

By a neural mechanism - innate releasing mechanism (IRM) and are triggered by a very specific stimulus - sign stimulus.

The IRM then communicates with the motor control circuits to activate (i.e. release) the FAP associated with that sign stimulus. ​

Question 49

Evidence of FAPs - Procedure

Tinbergen (1951)

Answer 49

Male sticklebacks are highly territorial during the spring mating season, when they also develop a red spot on their underbelly. If another male enters their territory, aggressive behaviour (FAP) is initiated. The sign stimulus is the sight of the red spot.

He presented them with a series of wooden models of different shapes.

Question 50

Evidence of FAPs - Findings

Tinbergen (1951)

Answer 50

Regardless of shape, if the model had a red spot the male stickleback would aggressively display and attack it. If there was no red spot, there was no aggression.
He also found that these aggressive FAPs were unchanging from one encounter to another.

Question 51

Evaluation of FAPs.

Fixed Action Patterns are not fixed. Hunt (1973)

Answer 51

He points out that the sequences of behaviours that appear to be fixed and unchanging are in fact greatly influenced by environmental factors and learning experiences. Therefore, FAP’s are more flexible than the name implies.
For instance, the FAP is typically made up of several aggressive behaviours in a series. The duration of each behaviour varies from one individual animal to another, and even within the same animal from one encounter to another.
This reduces the validity of the ethological explanation somewhat but not entirely, in the sense that, it does exist but how it works is not in the rigid way that it was first suggested to have worked.​

Question 52

Evaluation of FAPs.
Ethological explanations cannot explain cultural differences in aggression​
Nisbett (1993)

Answer 52

He found there was a north-south divide in the US for homicide rates. Killings are much more common amongst white males in the southern states than in the northern states. Because this is only true for reactive aggression triggered by arguments, Nisbett concluded that the difference in homicide rates was caused by a ‘culture of honour’, in other words the response to impulsive aggression was a learned social norm. ​

The ethological explanation finds cultural influences difficult to explain due to its views that aggression in instinctive. These cultural differences therefore question the validity of the ethological explanation.​

Question 53

What are the evolutionary explanations of aggression? #1

Answer 53

According to evolutionary explanations aggression can and does bring about benefits to those who use it. An evolutionary explanation of aggression is based on the premise that the human brain is a product of evolution by natural selection.
In particular, evolutionary psychologists believes that the human brain is comprised of a number of adaptions to cope with the various challenges associated with group living. These adaptions, including those that function to inflict costs on other humans, comprise our human nature (Duntley and Buss, 2004). ​

Question 54

What are the evolutionary explanations of aggression? #2

Answer 54

Aggression is a strategy that would have been effective for solving a number of adaptive problems among early humans. Solving these problems enhanced the survival and reproductive success of an individual, and as a result, this mental module would have spread through the gene pool. Mental modules have evolved in response to particular selection pressures faced by ancestral humans.

e.g. aggressive thoughts and behaviours are found to increase among males when resources such as territory, mates and food are scarce. ​

Question 55

What is sexual competition?

Answer 55

Ancestral male seeking access to females would have had to compete with other males. One way of eliminating the competition would have been through aggression (i.e. physical competition). Those individuals who used aggression successfully would’ve been more successful in acquiring mates and passing their genes.

This would have led to the development of a genetically transmitted tendency for males to be aggressive towards other males.

Question 56

Research example - sexual competition

Puts (2010)

Answer 56

He argues that various male traits seem to imply that competition with other males did take place among ancestral males. Anthropological evidence shows that, universally, males have thicker jawbones, which Puts believes may have come from men hitting each other, with the thickest-boned men surviving and passing on their genes to subsequent generations. Competition with other males may also explain why males have more robust skulls and brow ridges than women do.

Question 57

What is sexual jealousy?

Answer 57

A major motivator of aggressive behaviour in males, which can be an evolutionary explanation. This is because, unlike women, men can never be totally sure about whether or not they have truly fathered a child. This paternity uncertainty is a result of the threat for the male of cuckoldry (a male with an unfaithful partner) or having to raise offspring that is not his own. Any investment in offspring that do not share the male’s genes is a waste of his resources and it contributes to the survival of a rival’s genes and leaves the ‘father’ with fewer resources to invest in his own future offspring.​

Question 58

Margo Wilson and Martin Daly (1996) - mate retention strategies

Answer 58

• Direct guarding-involves male vigilance over a partner’s behaviour.
• Negative inducements- such as issuing threats of extreme consequences for infidelity (‘I’ll kill myself if you leave me’)​

Such behaviours are clearly linked to violence.

Question 59

What did Margo Wilson et al. found?

Answer 59

That women who reported mate retention strategies in their partners (they agreed with statements like ‘He insists on knowing who you are with and where you are at all time’) were twice as likely to have suffered physical violence at the hands of their partners. Of these women, 73% required medical attention and 53% said they feared for their lives.​

Question 60

Aggression in warfare.

Answer 60

War is very dangerous and costly and therefore is difficult to understand why an organism, selected to survive, should engage in behaviours associated with such extreme personal cost and danger. An evolutionary explanation would suggest that any behaviour associated with warfare would have evolved because of the adaptive benefits for the individual and their offspring. Livingstone Smith (2007) claims that human warfare originated not only to obtain valuable resources but also to attract mates and forge intragroup bonds.​

Displays of aggressiveness and bravery are attractive to females, and the absence of such displays reduces the attractiveness of individual males.

Question 61

Evaluation of evolutionary explanations of aggression.

Research support - Todd Schackelford (2005)

Answer 61

He studied intimate partner violence (IPV) in heterosexual couples.​

Procedure: Men and women in 107 married couples completed different questionnaires. All of the participants had been married less than one year. The men completed the Mate Retention Inventory, which assessed mate retention behaviours in various categories (such as direct guarding). The women completed the Spouse Influence Report, which measured the extent of their partner’s violence in their relationship. ​

Findings: There was a strong positive correlation between men’s reports of their mate retention behaviours and women’s reports of their partners’ physical violence. So men who used guarding (e.g. coming home early) or negative inducements (e.g. Threats to kill) were more likely to use physical violence against their partners.

Question 62

Evaluation of evolutionary explanations of aggression.

Strength

Answer 62

Many research studies demonstrate that mate retention strategies are associated with jealousy and aggressive behaviour. There seems to be a clear link between cuckoldry and aggression which supports the predictions derived from the evolutionary explanation concerning the adaptive value of aggression. ​

Question 63

Evaluation of evolutionary explanations of aggression.

limitation

Answer 63

Aggression is not universal - Kung San people of the Kalahari

Question 64

What are the 2 social-psychological explanations of aggression?

Answer 64

• Social learning theory

- Social theory: De-Individuation