Neural & Hormonal explanations of Aggression & Genetic Factors Flashcards
Name neurotransmitters associated with aggression
Serotonin
Dopamine
Name the brain regions associated with aggression
Amygdala
Prefrontal cortex
Where is the amygdala located?
Temporal lobe
What does the amygdala affect?
Emotional responses
The amygdala has been shown to be connected to the….
Prefrontal cortex
What does the term lesioning mean?
Damaging the brain on purpose
What’s an amygdalectomy?
Removal of the amygdala
What did research show when monkeys brains were lesioned?
Led to a reduction in fear and increase in aggression.
In humans, the removal of the amygdala can affect emotional responses
What happens if someone’s prefrontal cortex is damaged?
Show impulsive behaviour, immaturity, altered emotion, short tempers and are easily provoked
What effect does serotonin give?
A calming effect
What is dopamine responsible for?
Rewarding sensations
Pleasure. E.g. Sex and eating
Low levels of serotonin…
Increased aggression
Why is dopamine associated with aggression?
May seek out rewarding sensations aggression releases
Research into the neural explanation of aggression
Raine et al
Tateno
Zagrodzka
Research of Raine et al
PET scans of 41 murderers (39 males, 2 females) who were pleading NGRI
Had low activity in their prefrontal cortex
Research of Tateno et al
89 male patients with TBI
Aggression measured from various sources - family interviews, police records, accounts from friends
Those who were classified as aggressive, were more likely to have frontal lobe damage
Van Elst
Amygdala was reduced by 20% in violent offenders
Research of Zagrodzka
Damaged cats central nucleus of their amygdala. Predator like attacks
(Supported by Potegal - aggressive hamsters have more active neurons in the medial nucleus of the amygdala)
What is testosterone?
A hormone involved with aggression
Evaluation of the neural explanation of aggression
Supporting research for the role of the amygdala and prefrontal cortex
Too simplistic
Scientific
Based on animal research (can you apply the research to humans)
Deterministic
What is the endocrine system?
It produces several hundred hormones that interact with each other and the nervous system to regulate many different behaviours.
What’s the role of hormones?
To regulate and control bodily functions
When do levels of testosterone peak in males?
Around the start of puberty
What is castration?
To remove the testes
Castration….
Decreases aggression by removing the testes you are removing testosterone
Testosterone acts on the ‘_____’ system..
Serotonin system.. Lowers amount of serotonin (low levels of serotonin = less calm)
Name the research for the hormonal explanation of aggression
Archer
Edwards
Van Goozen
Research of Archer
Meta analysis of 5 studies and found a low positive correlation between testosterone and aggression
Research of Edwards
Injected testosterone into neonate female rats, made them act like males when they were injected again as adults.
However, the female rats only given testosterone as adults did not react in this way.
Suggests early exposure to testosterone is important
What is cortisol?
Another hormone associated with agg. Released from adrenal medulla and is important in the body’s response to stress.
The lower the levels of cortisol the higher the levels of aggression
Research of Van Goozen
15 male to female
35 female to male
Questionnaires assessed ‘proneness to aggression’ completed before and after receiving hormone treatment
Research showed female to male transsexuals reported an increase in aggression proneness, male to females found decrease
People with high testosterone and low cortisol…
More likely to be aggressive than those with high testosterone and high cortisol
Evaluation of the hormonal explanation of aggression
Supporting research Too simplistic Animal research Methodological problems (testosterone - spine) Correlation all research
Genetic explanation of aggression is assessed by researching…
Twins and adoptees
What are identical twins called?
MZ twins
DZ twins are…
Non-identical twins
Why is research on twins interesting?
If aggression is genetic, if one twin is aggressive you would expect the other to be too
Why are adoptees interesting?
If biological parents are aggressive adoptees should be too regardless of the environment
Name the 2 twin studies
McGuffin and Gottesman
Christiansen
Name the 2 adoption studies
Hutching and Mednick
Rhee and Walden
What is a concordance rate?
The likelihood that if one twin is aggressive, the other one will be too
Research of McGuffin and Gottesman
Found concordance rate of 87% for aggressive and anti-social behaviour for MZ twins and 72% for DZ twins
Suggests genetics are important
But that environment also plays a role
Research of Christiansen
Reviewed 3568 pairs of twins born between 1881 and 1910 in a region of Denmark
926 were registered by the police for criminal activity
35% concordance rate for MZ male twins and 21% for MZ female twins
12% concordance rate for DZ male twins and 8% for DZ female twins
Research of Hutching and Mednick
Study in Denmark involving a review of 14,000 adoptions in Denmark
Found a significant positive correlation between the number of convictions for criminal violence among the biological parents (particularly the gathers) and the number of convictions for criminal violence among their adopted sons
Research of Rhee and Walden
Meta-analysis of 51 twin and adoption studies involving 87,000 individuals.
Operationalised aggression as:
1 psychiatric diagnoses (antisocial personality disorder
2 delinquency
3 behavioural aggression
They suggested aggression could be explained in terms of 40% resulting from genes and 60% from environment
How many neurotransmitters are thought to be involved in aggression? Name them!
1) Noradrenaline
2) Dopamine
3) Serotonin
Imbalances of the three neurotransmitters lead to what?
Aggression
What is noradrenaline?
Related the fight/flight response and leads to increased alertness.
The fight/flight response may therefore be over active if noradrenaline is not broken down.
What is MAOA?
A chemical that keeps the neurotransmitters noradrenaline, dopamine and serotonin in check
If MAOA is not produced it leads to imbalances in the 3 chemicals
If the gene that produces MAOA is faulty…
No production of MAOA which leads to imbalances in chemicals which leads to aggression
Evaluation points for twin research studies
Twins are likely to share the same environment
Twins are often treated the same
Evaluation of adoption research studies
The adoption process may influence aggression
The contamination effect may play a role
Evaluation of the genetic explanation of aggression
Too simplistic
Deterministic
