Aggression & The Nervous System

Question 1

What links to aggression?

Answer 1

emotional behaviour

Question 2

how should we logically approach aggression research?

Answer 2

start with the brain areas dealing with emotions as hostile aggression is due to the intention to do so as a result of provocation

Question 3

What does the prefrontal cortex do in terms of aggression?

Answer 3

doesn’t ‘make’ emotions but has a big role in regulating emotions - the ventromedial prefrontal cortex deals with choices

Question 4

what does the ventromedial prefrontal cortex do in terms of choices and aggression?

Answer 4

if another area releases anger hormones, this area decides whether or not to act on these impulses

Question 5

What does damaging the prefrontal cortex, or existing damage in the prefrontal cortex do in terms of aggression?

Answer 5

Aggression could be seen in some people as an impairment on this region of the brain, so they’d have a harder time preventing themselves from not following through on their impulses.

Question 6

What study and explanation can help support the idea that deficiencies in the PFC leads to impulsive aggression?

Answer 6

Raine et al (1997) compared guilty parties stating themselves to be not guilty by reason of insanity (NGRI) with some non-offenders (control group). All participants had a 30 minute PET scan during cognitive tasks. Results found NGRIs have lower brain activity in certain areas such as the prefrontal cortex and amygdala - the regulators of emotion.

Question 7

What does Raine et al. 1998 look for?

Answer 7

Raine et al. (1998) carried out another study to see if different crimes have different activity patterns in their brain functioning. There were three groups:
Violent offenders with impulsivity and emotionally driven

Violent offenders with planned and predatory crimes
Control group (non violent)
Results found that with PET scanning evidence, there was lower prefrontal cortex activity in those who were emotionally driven and impulse based, in comparison to those who planned and were consistently predatory as well as the control group.

Question 8

Why is aggression present in the limbic system?

Answer 8

Aggression may therefore be present in the limbic system, as these structures are linked with self preservation instincts: this can include homeostatic responses, but also behavioural functions. It can contain structures like the amygdala and hypothalamus.

Question 9

What role does the amygdala have in aggression?

Answer 9

The amygdala is very involved in perceiving threats and retaliation of said threats. Upon removal of this, animals tend to be more passive and irresponsible, but also more aggressive when it is stimulated: damage may reduce responses to threats, perception of emotions as well as a marked diminished fear response.

Question 10

What studies can be used to show brain structure and functioning to be linked to aggression?

Answer 10

Downer 1961 ; Swanje 2012; Gorka et al. 2013 ; Anay and Veimati 1978

Question 11

How can Downer 1961 be used to show Brain structure and functioning to be linked to aggression?

Answer 11

Downer (1961) surgically altered monkeys brains to alter visual transmissions to the amygdala by removing one of them in their brain. Upon the transmission of people reaching the amygdala, they behaved more aggressively (their normal response) but were more docile and calm when this signal wasn’t received.

Question 12

How can Swanje 2012 be used to show brain structure and functioning to be linked to aggression?

Answer 12

Swanje (2012) used 20 healthy female volunteers for an MRI scan to calculate the size of the amygdala. They also took a self-report questionnaire (Life History of Aggression Assessment → LHAA) and used this to calculate their aggression scores. There was a negative correlation between the amygdala volumes and their aggression scores

Question 13

How can Gorka et al. 2013 be used to show brain structure and functioning to be linked to aggression?

Answer 13

Gorka et al. (2013) used FMRI scans to compare brain responses to emotional stimuli between people who were and weren’t drinking → alcohol is known as a factor in a large number of violent crimes and scenes of aggression. Results found participants who had drunk alcohol had less brain activity between the left orbitofrontal cortex, and the amygdala when presented with angry or fearful stimuli

Question 14

How is the hypothalamus involved within aggression?

Answer 14

The hypothalamus is involved in homeostatic responses such as hunger or seeking out food, but also in prey hunting animals, It also has a role in the attack behaviours i.e. a cat pounce on a rat due their hypothalamus’ electrical impulse. Parasites in rates make the loss of innate fear of cats through their suppression of the hypothalamus.

Question 15

How can Anay and Veimati 1978 be used to show brain structure and functioning to be linked to aggression?

Answer 15

Anay and Veimati (1978) altered the activity in the hypothalamus and basal ganglia of cats by using catecholamine neurotransmitters. If you decrease this, the cats would become more aggressive (hissing, scratching, biting etc.) but increasing it has the opposite effect

Question 16

What research methods are used in aggression and brain structure?

Answer 16

Laboratory Experiments
Correlational Analysis

Studies Using Animal Models
Brain Scanning

Question 17

define limbic system

Answer 17

a set of brain structures that includes the amygdala. It is important in the generation and regulation of emotional responses

Question 18

define amygdala

Answer 18

a brain structure that is important for experiencing fear in response to threats and also in recognising fear in other people. There are two amygdalae, one in each cerebral hemisphere.

Question 19

define hypothalamus

Answer 19

a brain structure involved in many homeostatic functions like eating. In predatory animals the hypothalamus is involved in generating predatory aggression and hunting responses

Question 20

define prefrontal cortex

Answer 20

the frontmost, outermost area of the brain. One of its functions is to decide whether or not to act on impulses generated elsewhere in the brain.

Question 21

What does damage to the corpus callosum do in terms of aggression?

Answer 21

inability to think through the consequences of their actions

Question 22

What were the aims of Raine et al. 1997?

Answer 22

To find out if there’s a difference in the structure of brain activity between people who have committed murder (NGRIs) and non-murderers - in particular the roles of the prefrontal cortex, the corpus callosum, the amygdala, the medial temporal lobe (MTL)/hippocampus and the thalamus in predisposing people towards aggression

To find out if the findings of studies linking brain structure to aggression in animals could be generalised to humans

Question 23

What was the independent variable for Raine et al. 1997?

Answer 23

whether the participant in an offender pleading NGRI or a non-murderer in the Control group

Question 24

What was the dependent variable for Raine et al. 1997?

Answer 24

relative glucose levels in the prefrontal cortex, the other lobes of the brain, the corpus callosum, the amygdala, the MTL/hippocampus and thalamus as revealed by the PET scan

Question 25

What were the participants like for Raine et al. 1997?

Answer 25

41 offenders pleading NGRI to the crime of murder (an opportunity sample) and 41 Controls. Within the offenders, there were 39 men and 2 women (with a mean age of 34.3) - 23 had a history of brain damage, 3 had a history of drug abuse, 6 schizophrenia sufferers, 2 epileptic and 7 with other emotional/learning disorders. The Controls were people of the same age and sex with no history of crime or mental illness, except 6 schizophrenic

Question 26

What was the procedure like for Raine et al. 1997?

Answer 26

They were tested at the University of California. Each was injected with a glucose tracer and performed a continuous performance task (CPT) for 32 minutes before the PET scan was carried out.

Question 27

What were the controls Raine et al. 1997 used in his study?

Answer 27

The participants were allowed to practise the CPT 10 minutes before the glucose tracer was injected to make sure they were all equally familiar with it He made sure none of the participants from both conditions was on medication - the NGRIs were kept free of medication for 2 weeks before the PET scan

Question 28

How did Raine et al. 1997 conduct a PET scan to effectively look at the different areas of the brain?

Answer 28

The PET scan was broken into slices and boxes, enabling Raine to measure the relative amount of tracer in each of the brain’s four main cortical regions and the 4 subcortical regions.

Question 29

What did Raine et al. 1997 find that was expected?

Answer 29

As expected, the NGRIs showed less activity in the frontal lobe, especially the prefrontal cortex which is associated with rational thinking, self-restraint and memory. There was also less activity in the parietal lobe which is associated with abstract thinking e.g. morality or justice, however there was more activity in the occipital lobe

Question 30

What did Raine et al. 1997 find in the subcortical regions/ hemispheres?

Answer 30

In the subcortical regions, the NGRIs had less activity in the corpus callosum which is associated with long-term planning. There was also an imbalance of activity in the right and left hemispheres in the limbic system - there was less activity on the left and more on the right, in the amygdala and MTL/hippocampus, and more activity on the right side of the thalamus - these are areas of the brain that are associated with aggression in animals.

Question 31

What did Raine et al. 1997 conclude in terms of brain abnormalities and anti-social behaviour/violence?

Answer 31

Prefrontal deficits may make someone more impulsive and emotional Deficits in the limbic system may make someone aggressive, as observed in cats: the amygdala controls urges and desires, the thalamus processes information and the hippocampus processes information → deficits may make it hard for someone to learn from their mistakes or understand their emotions Deficits in the corpus callosum make it harder for the hemispheres to communicate, making it harder to think through long term consequences and make decisions Areas such as the parietal lobe, the amygdala and hippocampus have a role in recognition - deficits here make it harder for someone to judge social situations, leading to overreaction

Question 32

What did Raine et al. 1997 conclude in terms of generalisation of animal studies?

Answer 32

He concludes that animal findings can be generalised to humans, and that there is a link between brain structure and aggression but he is optimistic that they can be prevented, if they’re identified earlier.

Question 33

What did Raine et al. 1997 warn about generalising his findings?

Answer 33

The finding only apply to this group of murderers pleading NGRI, not all voilence. He also claims that he isn’t claiming that violence is purely biological in nature, as he believes social and situational factors e.g. culture and upbringing also play a role. His results don’t show that the NGRIs had no freewill or they “couldn’t help themselves;” a brain structure only gives us a predisposition towards acting a certain way.

Question 34

What was a limitation in terms of the PET scan used in Raine et al. 1997?

Answer 34

They admit that this is the largest sample of the time looking at different areas of the brain with a control group however they admit that the PET images weren’t particularly clear and limited in how accurately they could be measured.

Question 35

What doesn't Raine et al. 1997's study show?

Answer 35

The study doesn’t show the causes of these brain deficits, nor that brain deficits can be linked to violence as not all NGRIs were accused of violent murders

Question 36

What was the generalisability like for Raine et al. 1997?

Answer 36

Large sample (82) which was the largest of its time - anomalies should not skew the data too much and thus making the results generalisable to the target population however NGRIs are unusual offenders, who aren’t representative of the target population - not all NGRIs commit violent murders.

Question 37

What was the reliability like for Raine et al. 1997?

Answer 37

PET scanning has been a reliable technique since the 1970s, producing objective and replicable results that can be tested and retested to check its reliability. The CPT ensures all participants were concentrating on the same thing, ensuring similar types of brain activity - standardised procedures But Raine admits of problems in the reliability of PET scans in the 1990s as results were sometimes unclear and had to be interpreted, which introduces subjectivity and low reliability.

Question 38

What was the objectivity/application like for Raine et al. 1997?

Answer 38

He suggests that if damage causing brain deficits can be prevented, people would not develop a murderous disposition - this involves early intervention with at-rish children in schools, programmes to steer young people away from drugs and monitoring those with brain damage. It may be possible to treat those with brain deficits as if these regions could be stimulated (drug therapy or counselling), they might be less likely to engage in impulsive, aggressive behaviour.

Question 39

What was the validity like for Raine et al. 1997?

Answer 39

As a natural experiment, it cannot show cause-and-effect. A similar idea is that it is learned behaviour as seen in the Bobo Doll studies by Bandura. The study only looks at brain activity which could be seen to be a reductionist view of human behaviour although Raine does make a point of explaining the personal, social and cultural influences that may also be at work

Question 40

How does Bufkin and Luttrell (2005) add to the construct validity of Raine et al. 1997?

Answer 40

Bufkin & Luttrell (2005) carried out a meta-analysis of 17 studies that used brain imaging to study aggression. They found all studies led to similar conclusions: impulsivity is linked to deficits within the prefrontal cortex or the amygdala. These add to the construct validity of Raine’s study as the results tie in with many other studies. The CPT can be criticised for being artificial and unconnected to violence or provocation, which could lower the ecological validity of the study.

Question 41

What were the ethics like for Raine et al. 1997?

Answer 41

NGRIs agreed to having the PET tests done as it would help their court cases, with controls giving their prior consent to be tested and for their imaging data to be used in the study. If the NGRIs/schizophrenic Controls weren’t competent enough to give consent, presumptive consent was given by their lawyer or carer. PET scans are invasive procedures as they have to be injected with a radioactive tracer - it is an unnecessary medical procedure for the Controls which increases the risk of research. The ethical concerns of the conclusions of this study as it seems to suggest someone may be driven to kill by their brain structure, inviting us to “screen” perspectives to check they don’t have a “murderer’s brain.” Once a study is released into the public eye, the conclusions can be misinterpreted, which would go against the social responsibility of ethical research

Question 42

What are hormones?

Answer 42

chemical messengers in the body

Question 43

How are hormones different to neurotransmitters?

Answer 43

work over time, in the bloodstream to relay messages

Question 44

What are the roles of hormones in the body?

Answer 44

affecting metabolism (the conversion of food into energy), mood, growth and development, as well as reproduction and sexual functions.

Question 45

does it take a large amount of hormones to make a difference in the body?

Answer 45

No - just a small amount

Question 46

What is the endocrine system made up of?

Answer 46

the thyroid, adrenal, thymus and pituitary glands as well as men’s testes/women’s ovaries

Question 47

What does the endocrine system do?

Answer 47

regulate physiology and behaviour e.g. breathing and temperature, tissue function, metabolic rate, reproduction, stress and growth and development, sleep and mood.

Question 48

Why is the pituitary gland important in the brain?

Answer 48

produces the growth hormone as well as adrenocorticotropic which produces cortisol, needed to combat stress and maintain healthy blood pressure/ This gland also produces antidiuretic hormones such as vasopressin which regulates water balance in the body and thyroid-stimulating hormones helping to regulate the body’s metabolism.

Question 49

How does the hypothalamus link to the pituitary gland?

Answer 49

it also produces hormones to help with body regulation

Question 50

What hormones do the thymus produce?

Answer 50

related to puberty

Question 51

What hormones does the pineal gland produce?

Answer 51

melatonin related to sleep

Question 52

What hormones do the testes produce?

Answer 52

testosterone, responsible for maintaining sex drive and producing sperm

Question 53

What hormones do the ovaries produce?

Answer 53

oestrogen and progesterone - role in menstrual cycle and development of breasts

Question 54

what hormones do the thyroid produce?

Answer 54

metabolism

Question 55

What hormones do the adrenal glands produce?

Answer 55

heart functioning and distributing stored fat

Question 56

what hormones do the parathyroid produce?

Answer 56

good bone development

Question 57

what hormones do the pancreas produce?

Answer 57

healthy levels of blood sugar

Question 58

How do hormones work?

Answer 58

they work by binding to receptor proteins in target cells and changing cell function - they cells should respond in a particular way to hormones

Question 59

Could hormone secretion be triggered by other hormones?

Answer 59

Yes or by activity at the neuronal level

Question 60

How is behaviour affected by hormones?

Answer 60

based on when they're released, how they're received at the cell level and receptors attached and the concentration of the hormone

Question 61

Can the environment affect the release of hormones?

Answer 61

Yes e.g. by stress or ling

Question 62

Can be hormones be used as medication?

Answer 62

yes

Question 63

How can oestrogen/progesterone be used in medicine?

Answer 63

as contraceptives or in hormone replacement therapy to prevent menopause symptoms

Question 64

How can insulin be used in medicine?

Answer 64

by diabetics or in steroid creams for skin disorders

Question 65

How is thyroxine used in medicine?

Answer 65

by those with thyroid problems to regulate the body

Question 66

How are steroid hormones used in medicine?

Answer 66

for autoimmune disorder

Question 67

How are glucocorticoids used in medicine?

Answer 67

to reduce inflammation

Question 68

What is the difference between neurotransmitters and hormones in terms of speed of travelling through the body?

Answer 68

Hormones travel over a large distance over a longer period of time (and so can be measured in seconds, minutes or hours) through the circulatory system and have varying levels of intensity depending on the concentration of the hormone. Neurotransmitters, on the other hand, have a very quick signal, being measured in milliseconds but it is restricted to appropriate neurons and can be said to be a ‘hit or miss’ form of signalling

Question 69

What significance does Dabbs et al. 1987 have in terms of hormones and aggression?

Answer 69

Dabbs et al. (1987) measured the level of testosterone in 89 male prisoners involved in violent and non-violent crime and found that the higher testosterone levels correspond with those implicated for more violent crimes → 10/11 prisoners who’d committed violent crimes had higher levels of testosterone with 9/11 in those with low levels of testosterone being more likely to commit non–violent crime. This suggests higher levels of testosterone do link to aggressive behaviours.

Question 70

What significance does Barzman et al. 2013 hold in terms of hormones and aggression?

Answer 70

Barzman et al. (2013) recruited 17 boys aged 7-9 years old from a psychiatric hospital to see if they could find hormones within their saliva that corresponded with aggression (testosterone, dehydroepiandrosterone [DHEA], and cortisol). They carried out 2 rating scales upon admittance, measuring aggression (one of which was the Brief Rating of Aggression by Children and Adolescents [BRACHA]) - saliva samples were taken thrice in the first 24 hours (once after they woke up, once 30 minutes after they woke up and once between 3:45pm-7:45pm) with nurses recording visible signs of aggression twice a day using a scale. They found the cortisol amount (30 mins after waking up) corresponded with the number of aggressive responses recorded by the nurses but this amount decreased over the duration of the day. DHEA levels correlated with amount of aggression in the first aggressive incident of the day - the aggression rating on admission was higher for those noted by nurses as ‘aggressive’ than ‘non-aggressive’ and so it was concluded that rating of aggression using BRACHA and that there are links between salivary hormones and aggressive behaviours of children in psychiatric hospitals.

Question 71

What significance does Adelson 2004 have in terms of hormones and aggression?

Answer 71

Adelson (2004) reported rats showing activity in the aggression systems in their brains also showed a hormonal stress response: as rats have a similar neurology to humans, researchers believed demonstrating a feedback loop between the hormonal stress response and brain aggression systems may help understand human aggression responses. The aggression control centres were electrically stimulated and showed hormonal stress responses - raised stress hormones coincided with higher electrical stimulation and vice versa. They concluded that this was a feedback loop that had been found. Adelson (2004) also reported stimulating the hypothalamus in rats, leading to a release of corticosterone (a stress hormone) - there was no fighting involved. Another study removed the rat’s adrenal gland (to prevent stress hormones from being released) and then injected corticosterone, whose immediate effect was to stimulate the hypothalamus - this supports the idea of there being a feedback loop between stress hormones and the brain’s attack system.

Question 72

What significance does Chang et al. 2012 have in terms of hormones and aggression?

Answer 72

Chang et al. (2012) looked at fish behaviour using the mangrove rivulus fish, focusing on aggression (measured by how the fish reacted to its mirror image in terms of aggressive displays) and exploring behaviour (how ready the fish was to approach a new shelter). They also looked at boldness (readiness to emerge from shelters), and learning (likelihood of fish entering the correct reservoir in a maze) - their aim was to link these flour behaviours to hormones, in particular, cortisol and testosterone. They found that aggression, exploring and boldness all correlated with the amount of testosterone present before the behaviours were exhibited as well as cortisol

Question 73

What significance does Montoya et al. 2011 have in terms of hormones and aggression?

Answer 73

Review conducted by Montoya et al. (2011) shows how testosterone/cortisol balance predicts impulsive and instrumental aggression.

Question 74

What significance does Dabbs et al. 1991 have in terms of hormones and aggression?

Answer 74

Dabbs et al. (1991) found a relationship between testosterone, cortisol and aggression with 113 offenders but only found that low levels of cortisol made aggression link to testosterone - cortisol is released in response to environment and that response gives high testosterone. Cortisol is linked to social withdrawal, not aggression

Question 75

What studies are there against generalisation of animal studies to humans?

Answer 75

Trainor 2009 ; and Sluyter et al. 2003

Question 76

How is Trainor et al. 2009 against generalisation of animal studies to humans?

Answer 76

Trainor (2009): Mice are in artificial situations when brain centre of aggression and hormone links are studied, and they have different social behaviours (male mice not aggressive to females whereas human males are) - ungeneralisable

Question 77

How is Slyter et al. 2003 against generalisation of animal studies to humans?

Answer 77

Sluyter et al. (2003): Although mice and humans share 90% of their genes, there is sufficient evidence to say there are enough differences to prevent generalisation

Question 78

How is Trainor et al. 2009 also for generalisation of animal studies to humans?

Answer 78

Trainor (2009): Hypothalamus and limbic systems in humans and rodents are similar enough for generalisation - attack centre found in hypothalamus

Question 79

Define hormone

Answer 79

a chemical messenger that may alter the structure or functioning of an organ or organ system. Hormonal messages tend to be longer lasting than neural messages, and they often affect a much larger area.

Question 80

define endocrine gland

Answer 80

a biological structure that releases one or more hormones. Collectively, the system of glands and hormones is called the endocrine system.

Question 81

define testosterone

Answer 81

an androgen hormone, found in males and females but usually at a higher level in males. It affects the development of the sex organs, bone structure and skeletal muscles. It also may affect behaviour in various ways.

Question 82

define organising effect

Answer 82

the effect a hormone has in influencing the structure of an organ. Exposure to testosterone during development alters the structure of parts of the hypothalamus, amygdala and hippocampus.

Question 83

define activating effect

Answer 83

the effect a hormone has in influencing the functioning of an organ. In the brain, testosterone can act like a neurotransmitter, binding to receptors in the amygdala and enhancing its activity.

Question 84

What did Duke et al. 2013 find out about the serotonin aggression hypothesis?

Answer 84

Duke et al. (2013) carried out a meta-analysis to look at the serotonin-aggression hypothesis and said the inverse relationship between serotonin and aggression may not be entirely accurate when looking at collections of studies. There are not always definite conclusions and the body of knowledge being built up by studies can be questioned.

Question 85

What is the serotonin aggression hypothesis?

Answer 85

Drugs increasing serotonin production lead to reduced levels of aggression, suggesting that low levels of serotonin are linked to increased aggression

Question 86

Why did Duke et al. 2013 caution against a conclusion about the serotonin-aggression hypothesis?

Answer 86

Low levels of serotonin was linked to higher aggression (to a small extent) but issues with the methods and study findings cautioned them against drawing overall conclusions of an inverse relationship between serotonin and aggression.

Question 87

How can researchers improve their understanding of the serotonin-aggression hypothesis?

Answer 87

To improve, they suggested researchers take care not to use selective reporting and to also report contradictory findings. Reliability and Validity of measures used in studies must be emphasised, with an examination of environmental and personality factors that may address this link and the complexity of how serotonin may affect brain functioning.

Question 88

Why is Dabbs et al. 2013 important when evaluating a study?

Answer 88

they highlight issues of validity and reliability, issues of careful measurement of the variables under examination and dangers of reductionism in looking closely at aspects of functioning without considering other possible variables.

Question 89

What results did Dabbs et al. 2013 find in his metaanalysis?

Answer 89

He examined 173 samples and around 6,500 participants and found a correlation of -0.12, showing a small inverse relationship between serotonin and aggression, showing it to possibly hold some basis in fact. He looked at four methods used to study the hypotheses and found differences in the strength of the correlation using the different methods.

Question 90

What are the strengths of considering the role of hormones in aggression?

Answer 90

Careful controls when looking for correlational evidence e.g. Barzman et al. (2013) - even stronger control when using animal studies e.g. Chang et al. (2012): scientific methods are used so there is scientific credibility - findings also support one another so is reliable Human and animal studies find a link between hormones and aggression through different methodology and measures so gives scientific credibility and reliability

Question 91

What are the weaknesses of considering the role of hormones in aggression?

Answer 91

In humans, there tends to be correlational data so cause-and-effect conclusions cannot be drawn - the origin is never known The explanation given about hormones and aggression, when investigated further, links to neurotransmitter functioning and brain structure/function too as well as natural selection - the study of human aggression is reductionist Not easy to generalise animal studies to humans with issues arising through differences in motivation and planning - this may not be helpful

Question 92

What are the important evidences to consider when thinking about aggression and hormones?

Answer 92

Neave & Wolfson (2003); Dabbs et al. (1995); Tricker et al. (1996)

Question 93

Why is Neave & Wolfson 2003 important when thinking about aggression and hormones?

Answer 93

Neave & Wolfson (2003) measured testosterone levels in male footballers before (1) a ‘home’ match; (2) an ‘away’ match; and (3) a training session. They found that testosterone levels rose significantly more before a ‘home’ match. They link this with the territorial aggression found in many species, and suggest it may partly explain the ‘home advantage’ that sports teams enjoy

Question 94

Why is Dabbs et al. 1995 important when thinking about aggression and hormones?

Answer 94

Dabbs et al. (1995) measures prisoners’ salivary testosterone levels and correlated this with their record of offending and their disciplinary record in prison. Those with the highest testosterone levels also were more likely to have committed violent offences and tended to have more prison rule violations on their record.

Question 95

Why is Tricker et al. 1996 important when thinking about aggression and hormones?

Answer 95

Tricker et al. (1996) did an experimental study in which men were randomly assigned to receive either a drug to increase their testosterone levels or a placebo. Measures of aggression were taken from the men themselves and also the people around them. No effect of testosterone was found, suggesting that the relationship between testosterone and aggression is not a straightforward causal one.

Question 96

What research methods are used when thinking about aggression and hormones?

Answer 96

Research in this area has relied heavily on studies using animal models. Research with humans has tended to use correlational designs. The best quality evidence comes from experimental studies, but these are relatively less common.