Aggression

• Limbic theory 


  Involves the amygdala, hypothalamus, and hippocampus
• What is the amygdala responsible for?

  Attaching emotional significance to sensory behaviours
• Damage to the prefrontal cortex reduces the inhibition of the amygdala, resulting in higher levels of aggression
• Kluver and Bucy


  Found that destroying the amygdala in rhesus monkeys reduced aggression
• Pardin


  Found that a reduced amygdala volume was positively correlated with aggression. As the amygdala evaluates the emotional importance of sensory information, a reduced volume would suggest an inability to do this, making violence more likely
• Hypothalamus


  Regulates the autonomic nervous system, which regulates responses to emotional circumstances. Damage to this area can result in an inappropriate aggression response to a perceived threat
• Hippocampus


  Forms long-term memories. Previously experienced aggression will be remembered
• Boccardi et al. (2010)


  Found that habitually violent offenders exhibited abnormalities in hippocampus function
• Raive


  Found that violent criminals had asymmetry in the size of the hippocampus within each hemisphere This impairs the ability of the hippocampus to communicated with the amygdala, leading to incorrect processing of sensory information and therefore aggression
• Serotonin


  Acts on frontal areas of the brain to inhibit the firing of the amygdala. Low levels leads to an inability to control impulsive and aggressive behaviour and affects response to external stimuli, meaning the person becomes aggressive easily. Can’t anticipate risk and therefore impulsively engage in aggressive behaviour
• Low levels of serotonin are linked ti uncreased susceptibility to impulsive behaviour, aggression, and violent suicide
• Mann et al


  Gave 35 healthy participants a drug which depletes serotonin. Using a questionnaire to assess hostility and aggression levels, they found that the drug in males (but not females) was associated with an increase in hostility and aggression
• What does Mann et al’s research tell us about neural explanations of aggression?

  They may suffer from beta bias
• Evaluate neural explanations

  • Research support for the role of serotonin. In research with vervet monkeys, reducing serotonin levels increased aggression whilst increasing serotonin decreased aggression
• Hormonal explanations


  Explanations for behaviour based on the role of hormones
• Research support for testosterone

  • Beeman (1947) castrated male mice and found that their aggression reduced
  • Beeman later injected the mice with testosterone, which re-established their aggression
  • Castration is now used for reducing aggression in animals
• Dabbs' research


  • Measured testosterone in saliva of 692 adult male prisoners
  • Found higher levels in rapists and violent offenders than burglars and thieves
• Carre and Olmstead's research


  • Testosterone levels fluctuate in response to context
  • Violent crimes may be a response to environmental stimuli
• Testosterone


  Correlated with aggression
• Ethological explanations


  Explanations that seek to understand human (or animal) behavior by studying them in their natural environment
• Ethological explanations


  • Propose that aggression evolved automatic, innate responses in animals
  • Believe animals have a built-in neural structure that will cause the release of automatic behavioral responses when exposed to specific stimuli (such as facial expressions)
• Fixed Action Patterns (FAPs)

  • Occur in the same way (stereotyped)
  • Are present in all conspecifics (universal)
  • Are innate and cannot be changed
  • Once triggered, the behavior must be completed (ballistic)
• Hydraulic model


  • Each FAP has a specific trigger (sign stimuli) that can release a reservoir of action-specific energy (ASE)
  • Once the FAP has been performed, the reservoir needs time to build up again before the FAP can be repeated
• Aggression is used to establish/protect territory and hierarchy
• Aggression rarely leads to death of the invader but defeats prompts the defeated individual to look for a territory further afield which is beneficial for the species
• Being at the top of the hierarchy gives access to more resources and, in males, gives privileged access to females
• When aggression takes place within species (intra-species), aggression is ritualised, it occurs in a series of steps carried out in a set order and end with appeasement displays from the "defeated"
• Aggression is thought to be evolutionary therefore ethologists argue that we are born with physiological structures eg neural circuits, which produce aggression
• Innate Releasing Mechanism (IRM)


  An innate system that responds to a stimulus in the environment to produce a pre-programmed fixed action pattern (FAP)
• Fixed Action Patterns


  • Three-spine stickleback males attack other males with red bellies that invade their territory
• Tinbergen (1951) provided evidence for the existence of FAPs in three spine sticklebacks
• Lorenz


  Species have instinctive inhibitions that prevent them from using weapons on their own species. E.g. if two wolves are fighting and one exposes their neck, instinctive inhibitions stop the other one from continuing the fight
• Ethological explanations evaluation

  • Lorenz underestimated the role of the environment. Lehrman
  • Humans don’t have FAPs for aggression. Eibl-Eibesfeldt: smiling and eyebrow flash
  • Ritualised aggression in humans
• Social learning theory


  Social-psychological explanation of aggression
• Observational learning


  Learning through observing someone’s behaviour
• Vicarious reinforcement


  Observing someone being reinforced for a behaviour and therefore being more likely to replicate it
• Vicarious punishment 


  Observing someone being punished for a behaviour and therefore being less likely to replicate it
• Model


  A person whose behaviours we want to imitate
• SLT meditational processes

  • Attention
  • Retention
  • Motor reproduction
  • Motivation
• Self-efficacy


  The extent to which our actions will achieve a desired goal. Aggressive behaviour may lead to us getting something we want, so we’re more likely to repeat it