Psychology Aggression Case Study


Aggression is a form of self-assertion (putting yourself forward or standing up for yourself). However, it is done through causing harm to yourself, to other people or to your environment. This can be physical harm involving breakages and bruises or mental harm, involving fear and anxiety. Physical aggression is violence and social aggression includes rumour spreading, insults and breaking off friendships. Threatening someone is aggressive because it causes them fear and anxiety, even if no violence occurs.
Aggression can take many forms but it is defined as any action that is aimed at causing either physical and/or psychological pain to oneself to others or to objects in the environment. The expression of aggression can occur in a number of ways, including verbally, mentally and physically - Charlotte Thomas (2012)
There are two camps when it comes to the psychology of aggression: the nature camp and the nurture camp.

Nativists (nature) argue that aggression is innate - it comes from within us. We are born with aggressive urges which never entirely go away, although self-discipline and a good upbringing might help us to control or re-direct these urges.
Nurturists (nurture) argue that aggression comes from our environment and no one is born aggressive. Aggressive behaviour is learned or else produced by social pressures. Put anyone in the right situation and they will behave aggressively, but anybody's aggressive behaviour can be reduced or removed if they are put in better surroundings.
  • In the Social Approach, Milgramshows how an authority figure will produce aggression (delivering electric shocks); Sherifshows how out-group discrimination turns into aggression in the Robbers Cave study
  • In the Learning Approach, Bandura shows how aggression is transmitted through aggressive role models; it may also be conditioned through reinforcement (Skinner)or association (Pavlov)
  • Although the Edexcel course doesn't cover it, the Cognitive Approach would also explain aggression, either as a rational choice (weighing up the costs and benefits to get what you want) or as faulty thinking (failing to appreciate the costs of aggressive behaviour)
Do we teach boys sports like rugby so that they can get rid of their innate aggression safely and productively... or are we teaching boys to be aggressive who wouldn't be otherwise?


The nativist view is that aggression is a response that is produced in the brain. There is evidence to support this from animal studies, brain scans on humans and case studies of individuals with brain damage.
Amazingly, Gage survived the accident, thanks to treatment from Dr John Martyn Harlow. However, his personality greatly changed. In his case study, Harlow reported that Gage became
fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires - John Harlow (1868)
After he died, 12 years later, Gage's skull was preserved and studied. Modern computer-assisted design has reconstructed the damage to his brain: it was damage to the frontal lobe, which is responsible for decision-making and self-restraint.
Before the shootings, Whitman had visited 5 doctors and a psychiatrist for help with his urges.
I talked with a Doctor once for about two hours and tried to convey to him my fears that I felt overwhelming violent impulses
The psychiatrist noted in his records that Whitman was "oozing with hostility". When an autopsy was carried out after the shootings, Whitman was found to have a brain tumour the size of a pecan nut pressing on his amygdala. A Commission that investigated the case concluded that this brain damage may have been responsible for Whitman's behaviour.


As the Phineas Gage case suggests, the brain's frontal lobe plays an important part in decision-making and self-restraint. In particular, a region called the pre-frontal cortex seems to be particularly important. If it is damaged or malfunctions, aggression is a possible side-effect.

Another brain structure that plays a role in aggression is the corpus callosum that links the left and right hemispheres. The two hemispheres need to communicate over long-term planning and thinking through consequences. Damage to the corpus callosum might also lead to more reckless behaviour.

In the Classic Study by Raine et al. (1997), brain scans of a group of murderers revealed they had much less activity in the frontal lobe and corpus callosum compared to a control group of non-murderers.
It's important to note that damage to the frontal lobe or corpus callosum doesn't create aggression itself. It just makes you less self-controlled and more inclined to act on the spur of the moment, especially in unfamiliar or confusing situations. This MAY turn out to mean aggressive behaviour, but it doesn't have to.


The limbic system is a sub-cortical area - part of the "old brain" that we share with other animals. It is also the brain's emotion centre where our most basic urges and desires (appetite, sleep, sex drive, fear) are regulated. For example, the thalamus is the brain's "switchboard" which receives signals and sends messages out to all the other areas. The hypothalamus has an important role in producing hormones.

However, the most important part of the limbic system for understanding aggression is the amygdala. The amygdala takes information from the thalamus and interprets it as a threat or not; it produces fear or aggression, the famous "fight or flight" response. Of course, if the amygdala malfunctions, then things which are threatening will not produce a fear response - or else harmless events will be interpreted as a threat, producing aggression.  The case of Charles Whitman might be an illustration of this.
This 10-minute video looks at the link between the amygdala and the pre-frontal cortex. It also includes Adrian Raine talking about his famous study.
The relationship between the amygdala and the frontal lobe is very important. If the pre-frontal cortex is healthy, then willpower can resist the amygdala's urges of fear or aggression. In Adrian Raine's murderers, the amygdala behaved erratically and the pre-frontal cortex was under-active - a dangerous combination.
Animal studies also support the link between the limbic system and aggression. John Flynn carried out studies on cats in the 1960s, using electrodes to stimulate the amygdala directly. Egger and Flynn (1963) introduced a rat to the cat's cage and found that the two animals would ignore each other. However, when the amygdala was electrically stimulated, the cat immediately attacked and killed the rat. This is predatory aggression. Egger & Flynn found that stimulation of a different part of the amygdala caused the cat to ignore the rat and attack the experimenter! This is affective (emotional or fear-based) aggression.


Over 19 sessions, you can see that mouse aggression varied a lot, but after castration it clearly drops. When the mice are injected with 150 micrograms of testosterone a day, their aggression creeps back up to the old levels.
A study of prisoners (James Dabbs et al., 1987, 1995) found testosterone levels were higher in those who had been convicted of a violent crime. Those with high testosterone levels were rated higher by other prisoners for being "tough".
Mazur & Booth (1998) review studies showing that men with higher levels of testosterone are more likely to:
  • divorce, or remain single
  • be arrested (for offenses other than traffic violations)
  • to buy and sell stolen property
  • incur bad debts
  • use a weapon in fights

Mazur & Booth report a study of 2,100 male Air Force veterans who received four medical examinations over a ten year period: testosterone levels fell and remained low with marriage, and rose with divorce. These results are consistent with Mazur & Booth's reciprocal model: testosterone varies with a person's dominance. Unattached males need to be socially dominant in order to attract mates so testosterone levels rise when a male is single. This explains why single/divorced males are more likely to be convicted of crimes, even when the statistics are adjusted for individuals with certain characteristics like calmness and empathy being more likely to marry in the first place (Ryan King, 2007).
Another hormone linked to aggression is cortisol. Cortisol is a hormone produced in the adrenal glands. While it is responsible for "waking us up" in the morning, its main job is managing stress levels. Cortisol seems to inhibit aggression, the same way that testosterone increases it (Van Goozen et al., 2007). Virkkunen (1985) report low levels of cortisol in violent offenders and  Tennes & Kreye (1985) report low levels of cortisol in aggressive school children.
People with lower levels of cortisol are more aggressive because it means their autonomic nervous system (ANS) is under-aroused; aggressive behaviour is an attempt to create stressful situations which provoke cortisol release, stimulating the ANS.
There's also evidence linking aggression to HIGH levels of cortisol (eg. Gerra et al., 1997). Clearly, cortisol is complicated and does a lot of different things in the brain.
Animal studies also support the link between hormones and aggression. Rachel Adelson (2004) used rats as test subjects and used electricity to stimulate the hypothalamus; this led to the release of a stress hormone called corticosterone, which is part of the aggressive response. 

If the rats had their adrenal glands removed and couldn't produce their own hormones, their aggression faded. However, when they were then injected with corticosterone, the hypothalamus activated. This shows a "feedback loop" in aggression: the hypothalamus triggers the release of the hormone but the hormone also activates the hypothalamus. This might explain the phenomenon of rage, when aggression spirals out of control.


Serotonin is a neurotransmitter linked to mood and sadness. Treatment for depression often involves medicines that boost serotonin levels in the brain. However, low serotonin levels are also associated with increased aggression. This is because serotonin seems to inhibit aggression.
Dee Higley et al. (1996) studied rhesus monkeys living wild on an island. The researchers used behavioural observations of the monkeys fighting and leaping from trees. They also took samples of spinal fluid from the monkeys to measure 5-HIAA levels. 5-HIAA is a chemical that is produced by the re-uptake of serotonin, so high levels of 5-HIAA means high levels of serotonin. If serotonin inhibits aggression, you would expect aggressive monkeys to have low levels of serotonin, and therefore low levels of 5-HIAA (because there would not be need for much serotonin re-uptake).
The poor monkeys with low levels of serotonin got themselves killed jumping off trees and attacking older, bigger monkeys. Basically, being jerks.
There is also a link between dopamine and aggression. Dopamine is a neurotransmitter linked to attention and pleasure. Increased dopamine levels are associated with increased aggression and anti-psychotic drugs (which reduce dopamine levels in people suffering from schizophrenia) seem to reduce aggressive moods and behaviours.
Ferrari et al. (2003) studied the link between neurotransmitters and aggression in rats. They allowed a rat to fight every day for 10 days at approximately the same time. This was done by introducing an "intruder rat" into the test rat's cage. On the 11th day, no intruder rat was introduced. The researchers measured the levels of serotonin and dopamine in the test rat's brain. The test rat’s dopamine levels had increased and serotonin levels decreased, because it was anticipating a fight.

This study also links in with Classical Conditioning. The rat had been conditioned to fight at a certain time each day and its brain chemistry had altered to prepare it for aggressive action. It also illustrates brain plasticity, since the rat's brain chemistry changed, showing that the brain adapts to what we experience.
A famous example is Phineas Gage, an American railway worker who suffered a terrible accident in 1848. The railway workers used dynamite to make the ground flat for laying the rail tracks, but an unexpected explosion nearly killed Gage. It blasted a "tamping iron" (a metre-long iron nail) through Gage's skull; the iron entered through Gage's cheek, passed through his brain and shot out of the top of his head.
Another case study is Charles Whitman, a Texan marine who, in 1966, murdered his family then shot a dozen strangers in a killing spree, before taking his own life. Whitman left a suicide note:
I don’t really understand myself these days. I am supposed to be an average reasonable and intelligent young man. However, lately (I can’t recall when it started) I have been a victim of many unusual and irrational thoughts.
Testosterone is the hormone linked to aggression. Testosterone is produced in spurts, so the testosterone levels can rise suddenly and have an effect within minutes. It also varies seasonally in some animals, which is why red deer become aggressive in the mating period in the Spring. Males produce more testosterone than females (although female ovaries do produce testosterone) - and this is an explanation for why males are are aggressive than females on average.
Castration reduces testosterone levels in males. Wagner et al. (1979) castrated mice and observed that aggression levels dropped. When the castrated mice are injected with testosterone, their aggression levels (measured by biting attacks on other mice) rose back to pre-castration levels. This clearly suggests that testosterone is a cause of aggression in mice and may cause aggression in humans too.
The researchers found a negative correlation between 5-HIAA and aggression: aggressive monkeys had lower levels of 5-HIAA (and therefore of serotonin too); less aggressive monkeys had higher levels.

Low 5-HIAA/serotonin was associated with high risk-taking behaviour, such as aggression towards older, larger animals and taking long leaps from tree to tree. Many died as a result of this.


Sexual Jealousy

Sexual jealousy is a powerful cause of aggression, which is why it is the plot of so many great stories.
Sexual feelings also come from the limbic system. As part of its job in regulating emotions, the amygdala handles trust and intimacy. It is responsible for helping us recognise familiar faces and feel secure around people we are on intimate terms with. Sexual jealousy (when we feel insecure around people we are intimate with) is also produced by the amygdala.

Of course, some people just get unhappy when they are jealous; they don't get mad. Jealous rage seems to require hormones as well, such as testosterone in men. Testosterone is produced in the testes but the message to increase production comes from the pituitary gland in the brain, just beneath the limbic system.

Mazur & Booth (1998) showed how testosterone rises in men who need to show their dominance; this includes single males and males in failing relationships. If jealousy makes men feel insecure in a relationship, their body will start to produce more testosterone to prepare them to assert their dominance and this can make them aggressive.

One of the conclusions from all this is that the best way to reduce male aggression is to marry men off! This is the conservative idea that "men are civilised by marriage". A similar idea, popular with people of a different political outlook, is that the best way to reduce male aggression is to give more power to women.
Since violence is largely a male pastime, cultures that empower women tend to move away from the glorification of violence and are less likely to breed dangerous subcultures of rootless young men - Stephen Pinker (2011)
However, not everyone agrees that men need to be tamed. Schacht et al. (2014) carried out a meta-analysis of 20 studies into male violence in different countries. They found "that violence was equally likely to be associated with extra women as with extra men." Nine studies showed more violence in societies where men outnumbered women, and nine showed the opposite. Two studies were not conclusive.
Social Aggression

Not all aggression is physical aggression. There is also teasing, name-calling, rumour-spreading socially excluding people. Social aggression has two components:

  • Indirect aggression, which is covert (hidden), such as spreading malicious gossip
  • Relational aggression, which is overt (in the open) but non-physical, such as breaking off a friendship, pulling faces or “bitchiness”

Statistics on bullying show that 30% of children may be the target of it at some point in time (Analitis et al., 2009). A study by Atlas & Pepler (1998) revealed that other children were present in 85% of all bullying episodes on a school playground, yet these bystanders intervened to stop the bullying just 15% of the time.

Gordon Ingram (2014)shows that young children show more physical aggression than social aggression, but, as they grow into adolescence, this reverses and social aggression (gossiping, rumour-spreading) dominates.

Brendgen et al. (2015) considers this as part of the Biological Contemporary Study:  young children don’t have the verbal or social skills to practise social aggression, but they acquire these once they start school. The Brendgen study goes on to show a genetic connection in twins that links to social aggression as well as physical aggression.
In Shakespeare's play "Othello", the conniving servant Iago drives his master Othello mad with jealousy by making Othello think his beautiful young wife has given her handkerchief to another man. It all ends BADLY.



Human and animal studies support the idea that there are brain structures linked to aggression, in particular the limbic system which generates aggressive impulses and the pre-frontal cortex which inhibits aggressive impulses. Animal studies like those carried out by John Flynn in the 1960s clearly show the role of the limbic system in producing different sorts of aggression. Ferrari's research on rats illustrates how dopamine and serotonin are linked to aggression in rats. These animal studies are backed up by human studies, like Raine et al. (1997) which also suggests the amygdala and pre-frontal cortex are linked to murder, and case studies like Charles Whitman whose brain tumour may have produced his uncontrollable aggression.

Since the 1990s, this research has been supported by new brain imaging techniques like PET and MRI. These scans show a correlation between unusual brain activity and aggressive or antisocial behaviour, such as Adrian Raine's observation that there was 11% less activity in the pre-frontal cortex of patients suffering from Antisocial Personality Disorder compared to a Control Group.

This evidence supports the nativist viewpoint that aggression is innate, present from birth and an unavoidable (and even a positive) part of human behaviour.

Generalising from animal studies to humans is full of difficulties. Animals do not have the same pre-frontal cortex as humans (it is smaller, for example) and may not be capable of planning or self-awareness.

Animals also express their behaviour through dominance or submission. It is possible that researchers are confusing dominant behaviour with aggressive behaviour. This would be a validity problem with the animal model if one sort of behaviour is being mistaken for another. In fact, there may be very little aggression in animal behaviour:
The overwhelming impression one gets from watching animal disputes is of remarkable restraint and self-control. The spilling of blood is not the norm - it is a rare event  - Morris (1990)
If this is true, humans may be much more aggressive than other animals, especially when social aggression (which cannot easily be observed in animals) is taken into account.

Although brain imaging techniques are reliable, there may be validity problems with these too. This is because the same structures in the brain (and the same neurotransmitters) seem to do different jobs. For example, the amygdala regulates both aggression and fear. Dopamine is associated with both pleasure and aggression and both high and low levels of dopamine are linked to aggressive behaviour.
The Exam Board expects you to compare the biological explanation of aggression with the Freudian explanation of aggression. Freud's ideas are explained on another page. For now, I'll compare and contrast the biological explanation with the empiricist explanation that aggression is learned.
There are many studies supporting the idea that aggression is a learned behaviour. Bandura's "Bobo Doll" studies show that children imitate the aggressive behaviours they see in role models. Classical and Operant Conditioning both offer explanations for aggressive behaviour.
  • Classical Conditioning shows that aggression is an unconditioned response to some stimuli (like threat) but may become a conditioned response to a neutral stimuli (like social embarrassment, unfamiliar people or drunkeness). This ties in with the Biological Approach because it assumes that unconditioned aggression is an instinctive response, but conditioned aggression is learned.
  • Operant Conditioning shows that aggression is learned through reinforcement, either positive reinforcement (aggressive behaviour may bring you admiration and respect) or negative reinforcement (aggressive behaviour may make unpleasant things stop, by scaring people away).

Strict Behaviourists like B.F. Skinner would argue that ALL behaviour is learned and that human beings are born as tabula rasa (a bank slate), with aggression being added later.

Biological determinists would argue that ALL behaviour is hereditary and that human beings are born with a genetic destiny they cannot help but obey.

Most psychologists take a middle way between these extremes. Genetics gives us predispositions to behave a certain way, but we can resist these impulses if we try. We learn specific behaviours, but our genes give us broad instructions that affect what we learn and how easily we learn it.
  • For example, Watson & Rayner conditioned Baby Albert to fear a white rat, but their experiment depended on the fact that Albert found something naturally frightening (a loud noise).
11-minute video (part 1 of 4) looking at different theories of aggression, nativist and empiricist

If the nativist viewpoint is correct, then aggressive behaviour is natural and unavoidable. It might be possible to identify people with extreme aggression at an early age, either by genetic screening, testing for testosterone or serotonin levels or by trying to identify those with an under-active pre-frontal cortex or malfunctioning amygdala. These individuals could be carefully monitored and perhaps kept away from jobs or roles where they might present a danger to the public (working with children or in hospitals, for example). There might be some jobs that would suit them well (the Armed Forces, perhaps, or contact sports like boxing or rugby).
This viewpoint easily turns into EUGENICS, which is the belief that some people are biologically inferior and should be prevented from having children. This is an ethical debate that psychologists must consider.  This will also be discussed as part of the Key Question for the Biological Approach.
Another application of the nativist view of aggression is the use of drugs to control behaviour and reduce aggression. For example, young people with ADHD (Attention Deficit Hyperactivity Disorder) can behave aggressively. They are often treated with drugs like Ritalin to control their behaviour.
Many people feel there are ethical problems with controlling people through drugs, especially young people who might suffer side effects from the medication.

Interestingly, Ritalin works by (among other things) boosting dopamine levels to help children with ADHD to concentrate. High dopamine levels are normally associated with increased aggression. This illustrates the problems with linking dopamine to aggression and indeed with linking any biological process to aggression in a straightforward way. The exact effect dopamine has depends on a lot of other factors.

If the nativist viewpoint is mistaken, then identifying people based on biological tests and discriminating against them is grossly unfair. Not everyone with high testosterone levels is a violent person. This ties in with the objection that biological characteristics often relate to several different behaviours. High testosterone levels might make one person aggressive but another person hard-working and energetic. High dopamine levels are associated with aggression in some people, but good memory and cheerfulness in others.

The nurturist viewpoint would argue for the importance of education and counselling to help people manage their emotions and behave more appropriately. Techniques like Token Economy Programmes have been developed to do this based on the Learning Approach. Bandura's research suggests removing aggressive role models from TV and film might help reduce imitative aggression. However, if some people are driven by biological urges they cannot control (perhaps like Charles Whitman), then no amount of education or therapy will help them.

Most psychologists adopt an interactionist approach, accepting that aggression is produced by nature and nurture. This is the view taken by Mara Brendgen; even though her twin study suggests that physical and social aggression both have a biological connection, she concludes that education at an early age may help children control their behaviour better.

The idea of brain plasticity suggests that the brain changes based on experience. If so, then learning can change brain chemistry. This is illustrated in Ferrari et al.'s study of fighting rats.

How to write a 8-mark answer

Evaluate and apply the biological explanation of aggression. (12 marks)
  • A 12-mark “evaluate” question awards 4 marks for describing biological processes leading to aggression (AO1), 4 marks for applying biology to aggression (AO2) and 4 marks for evaluation (AO2). You need a conclusion to get a mark in the top band (7-8 marks).

Biologically, aggressive responses come from the brain's limbic system, which handles also our basic drives and emotions. In particular, the amygdala regulates fear and anger.
Aggression may also be due to a failure of the pre-frontal cortex to restrain aggressive urges. THe pre-frontal cortex handles decision-making and self-control.
Aggression may also be caused by a failure in the corpus callosum, because this enables the left and right hemispheres to communicate which is important for long-term thinking.
Finally, low levels of serotonin are associated with aggression; serotonin is linked to sadness and the ability to inhibit (restrain) your feelings.

Young children can be physically aggressive because they have not yet developed the cognitive skills to handle frustration and disappointment.
As they go through school, children switch to being socially aggressive rather than physically aggressive. This may involve verbal bullying and "being mean".
Brendgen's twin study found a genetic link for both types of aggression. MZ twins were more likely to be aggressive if their twin was aggressive.
Children with the gene for aggression may be counseled to help them show their feelings in less hurtful ways.

Biological explanations of aggression are backed up by studies like Raine et al., which use brain imaging to show parts of the brain that are less active in aggressive people.
Explaining aggression biologically runs into the problem that biological processes can lead to different behaviours. For example, the amygdala regulates aggression and fear.
The nurturist approach focuses instead on how we learn aggression from our environment. You can see this in studies like Bandura, Ross & Ross, where the children imitate the aggression they observe.
Although drugs can calm people with Antisocial Personality Disorders, the biological approach doesn't offer useful therapies like counseling which can help aggressive people manage their anger.

An interactionist approach includes both learning and biology. Because of brain plasticity, our brain structure may change because of our experiences, making us more or less aggressive than we were to start with.

  • Notice that for a 12-mark answer you don’t have to include everything about the biology of aggression. I haven’t mentioned the other parts of the limbic system, testosterone or the role of serotonin. But it is a balanced answer - one third description, one third application and one third evaluation.

Case Study- 4

Z. is a 9 year old boy who was referred by his mother regarding concerns she had around his behaviour at home. Z.’s mother identified the following problems – defiance (e.g. talking back to parents, defying parent’s authority, refusing chores at home and refusing to comply with house rules), behaviour management issues (e.g. inability to bring self under control when limits were set on the behaviour, having a tantrum when asked to stop an activity ). She reported no developmental issues. In addition Z.’s teacher recommended a cognitive assessment as he noted Z.’s excellent broad general knowledge; excellent reading with comprehension and his ability to promptly complete work accurately. His classroom teacher felt that Z. may be gifted.

In the first instance, Z. was assessed with the Wechsler Intelligence Scale for Children – Fourth Edition (WISC-IV). Z.’s unique set of thinking and reasoning abilities made his overall cognitive functioning difficult to summarise by a single score on the WISC-IV. He showed average to above average verbal skills and above average working memory skills; average nonverbal skills and below average processing speed skills. He did not fall within the gifted range of cognitive ability. Feedback and interventions were given with regards to the WISC-IV assessment with an emphasis on processing speed.

Z. was also assessed with the Child Behaviour Check List (CBCL). The CBCL results indicated very elevated range for the externalizing behaviours of oppositional defiant problems and also aggressive behavior. A course of Non Directive Play Therapy was commenced with Z. In addition his mother and father were provided with psychoeducation and also Child Parent Relation Training. Z.’s first nine sessions of Non-directive play therapy showed him mostly displaying acting out behavior with limit setting being the main focus. His parents reported his behaviour at home improving with a lessening of tantrums but he still remained defiant with regards to following parental instructions. Z. is continuing the sessions and will be assessed on the CBCL after 10 sessions.

Vinity Gill (Psychologist)


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