Neural and Hormonal Mechanisms in Aggresison Flashcards
What are neural mechanisms related to
the nervous system
What are hormonal mechanisms related to
the endocrine system
where is the role of the limbic system (in aggresion)
What did Papez and MacClean link it to?
It’s a key structure/region in the brain. Papex and Macclean linked it to having involvment in aggressive bahviours
What is the role of the amygdala
It generates emotions and attaches them to stimuli, then storing them in the emotional memory
What differences are seen between a Hyperactive and Hypoactive amygdala in offenders
Hyperactive: reactive aggression
Hypoactive: other offenders (e.g. psychopaths)
What type of amygdala response causes aggressive reactions
a fast and heightened response (e.g. hyperactive)
AO1/AO3
Potegal (1996) research into the amygdala and aggression
found that:
- stimulation of the amygdala increases aggression
- lesioning (i.e. preventing its functioning) reduces aggression
IN HAMSTERS
AO1/AO3
Groves and Schlesinger (1982): Research into the amygdala
+ AO3 point
found that surgical removal of the amygdala reduced human aggression in **previously violent individuals **
- This establishes a cause and effect relationship between the function of the amygdala and aggression
AO1/AO3 Supporting
Charles Whitman case study
Limbic System + Aggression
+ what this shows
Charles Whitman killed many people in Austin, and in the morning of he also killed his mother and wife.
- using a post mortem, it was discovered that Whitman’s brain had harboured a tumor that compressed the amygdala and also affected the hypothalamus
This shows there is a link between the manipulation of the hypothalamus/amygdala and aggressive behaviour.
What are the 2 functions of the hypothalamus
1: responsible for behaviours such as hunger and thirst, as well as maintenence of basal body tempurature (i.e. homeostasis)
2: It is responsible for motivational behaviour and control the pituitary glad which is the ‘master gland’ that controls all other glands in the endocrine system.
THE HYPOTHALAMUS THEREFORE PLAYS A KEY ROLE IN CONNECTING THE ENDOCRINE SYSTEM TO THE NERVOUS SYSTEM
AO1/AO3
Flynn (2006) research into the hypothalamus and aggression
AO3: what this suggests
- stimulating the lateral (side) area of the hypothalamus in cats led to predatory aggression (catching and killing quickly and silently)
- stimulating the medial (muddle) of the hypothalamus led to rage aggression (arching back, hissing, baring teeth etc)
This suggests that different types of aggression are controlled by different areas of the brain and supports the effects of the hypothalamys on aggression.
AO1/AO3
Research into the limbic system and aggresssion
(41 psychopaths and 41 controls)
Researchers compared the brain of 41 psychopaths and 41 control PPT’s using PET scans
- They found there was an imbalance of activity between the left and right hemispheres in the limbic system in psychopaths
- There was less activity on the on the left side of the brain and more activity on the right in both the amygdala and hypothalamus)
These areas are associated with aggression in animals, and now we have human evidence to support this.
- This also supports the use of animal studies due to the similarity in findings, showing their use is important and valid in neural research.
What is the role of serotonin + (Cases 1995)
Serotonin is an inhibitory neurotransmitter which is associated with a greater degree of self control.
Cases (1995): it calms neuronal firing in the brain,
what are normal levels of serotonin in the orbitofrontal cortex associated with
Normal levels of serotonin in the orbitofrontal cortex inhibit neurons (reduce action potentials + firing) are are linked to a greater degree of self control.
What happes if there are low levels of serotonin in the brain
Low levels remove the inhibitory effect the neurotransmitter has in normal brains - people are therefore less able to control impulsive and aggressive behevaiour
What effect does serotonin have on the amygdala and as a result on aggressive behaviour
Serotonin typically inhibits the firing of the amygdala, meaning it controls aggressive impulses (because a hyperactive amygdala has been lined to reactive aggression)
AO1/AO3
Research into serotonin and aggression (amino acids)
Serotonin in manafactured from the amino acid tryptophan.
research on vervet monkeys (AO3: animal studies) showed that:
- reducing levels of serotonin resulted in an increased level of aggressive bahviour
- However feeding a diet rich in tryptophan resulted in a decrease in aggressive occurences (e.g. nuts)
What is testosterone
an androgen + the primary male sex hormone
What are hormones
Hormones are chemical messangers the regulate and control bodily functions - they are secreted from glands directly into the bloodstream.
What led to testosterone being a consideration as a factor linked to aggression
Males are generally more aggressive than females.
- It’s responsible for the development of masculine features and plays a role in regulating socialbehaviour (incl. aggression) via its influence on certain areas of the brain implicated on aggressuon.
AO1/AO3: Support
Dolan et al (2001) testosterone and aggression
+AO3 c/p
Dolan et al found a posiitve correlation between testosterone and aggression in male offenders with history of violent and impulsive behaviour
AO3: correlational studies - not causation.
AO1/AO3: Supporting
Berthold (1859): leg horn cockrels and aggression
transplanted testes into castrated male birds and observed that the aggression levels increased (testosterone is secreted from the testes)
- This establishes a relationship between testosterone and aggression
AO3: Weakness (of the neural/hormonal explanation of aggression)
Animal studies + generalisablity to humans
+C/P due to consistent findings between humans/animals
Mammalian brain systems are different to animals - even primates due to the structural differences in the cerebral cortex (which is responsible for functioning + emotional regulation)
- This means that tests on animals can’t be generalised to humans as there are structural differences in the brain that may lead to different outcomes
C/P: The study done on the 41 psychopaths that displayed the imbalance in activity beteen the right/left hemisphere shows the same findings when the study was repeated on animals.
- This shows that animal studies and human study findings are consistent and this improves the validity of using animal studies to generalise to humans.
AO3: Weakness (of the neural/hormonal explanation of aggression)
Biological Redictionsim
These studies reduce behaviour to a single function (the brain and biology) and fails to consider the role of society upon our behaviour.
It only attributes aggression to biology which may not be a holistic explanation of aggression.
- This means that the biological basis of aggression may lack so reliability as it fails to account for the environment which we know plays a crucial role in our behaviour due to research evidence from social thoeries such as the SLT and the Frustration Aggression Hypothesis
AO3: Strengths (of the neural/hormonal explanation of aggression)
Research support increases reliability
Research studies with similar findings increase the reliability and validity of findings.
- This is because if cross-study results are similar, this strengthens he thery as the trend in results remain consistent and diplays findings are more widespread and not due to PPT variables.
This improves the validity of findings and results and means our conclusions have better support ot be generalisable.
AO3: Weakness (of the neural/hormonal explanation of aggression)
Human Studies fail to demonstrate cause and effect
For example Dolan et al found that there is a correlation between high testosterone levels and aggression in males with a history of impulsive violent behaviour.
This however is only a correlational study as this is because it would be inethical to manipulate human brains as it could create a lasting impact.
This means as the varibales can’t be manipulated, we can’t establish a cause and effect relationship.
This reduces the validity of the conclusions drawn about behvaiour as we can never be 100% definite abou the cause of a behaviour.
AO1/AO3
Berman, Gladue and Taylor (2005): reaction time/shocks
+ C/P by Mazur (on dominance vs aggression) EVOLUTIONARY APPROACH
asked male PPT’s to take part in a reaction time competition where they could set the shock level given to the losing competitor. (the level of shcok was recorded as aggression)
- a relationship was found between salivary testosterone levels and aggression.
- Higher levels of testosterone = greater aggression
C/P: Mazur (1985) argued that we should distinguish between dominance behaviours and aggression. Dominance is intended to maintain or gain status (evolutionary) and acting aggressivley is one way of getting there.
- The evolutionary explanation would say that this behaviour is as a result of the male innate and adaptive deire to be of higher status which could be linked to higher testosterone
- - This would mean that the aggressive behaviour wasn’t the inention, but rather it was a natural instinct to ‘show who’s boss’ caused by testosterone, rather than aggression.
AO3: Strength (of the neural/hormonal explanation of aggression)
Real World Application: SSRI’s
Research onto the neural mechanims of aggression + impact of serotonin on the limbic system and its links to aggression gave rise to the use of SSRI’s + other drugs that act on neurotransmitters to be used as a treatment for aggression.
- This has real world implications as it can significantly improve quality of live for individual s
