Biological Psychology: Brain Structure and Aggression

Limbic System

  • Hypothalamus: Regulates hormones, sleep, mood, hunger, thirst, sexual arousal, blood pressure, body temperature, and heart rate.

  • Thalamus: Processes sensory information and aids memory, planning, and emotions.

  • Hippocampus: Responsible for forming new memories.

  • Amygdala: Influences emotions (anxiety, anger, fear), memory, social interpretations, and responses to environmental threats.

    • Coccaro et al (2007) found high amygdala activity in individuals with intermittent explosive disorder when viewing angry faces.

Prefrontal Cortex

  • The orbitofrontal cortex (OFC) works with the amygdala in aggression.
  • The OFC is involved in rational thinking, decision making, self-control, impulse regulation, and inhibiting aggressive behavior.
  • Reduced OFC activity is seen in psychiatric patients with violent tendencies.

Serotonin

  • Serotonin is an inhibitory neurotransmitter that slows down neural activity.

  • Normal serotonin levels in the OFC support self-control.

  • Decreased serotonin levels can lead to reduced self-control and impulsive aggression.

    • Virkkunen et al (1995) found higher levels of a serotonin breakdown product in the cerebrospinal fluid of violent, impulsive offenders.

Dopamine

  • Dopamine is both an inhibitory and excitatory neurotransmitter that regulates motivated behavior and reward experiences.

    • Dongju Seo et al (2008) proposed that serotonin underactivity stimulates dopamine overactivity which are both linked to impulsivity and aggression.

Evaluation of Biological Research into Aggression

  • Strengths
    • Pardini (2014): Amygdala volume negatively correlated with aggression after controlling extraneous variables.
    • Raine (1997): Classic study establishes link between brain activity and murders
    • Animal research: Electrical stimulation of the hypothalamus can result in aggressive behaviour (Andy and Velamati, 1978)
    • Application: Developing drugs (serenics) to modify serotonin levels could reduce aggressive behavior.
    • Brain scanning technology: PET and fMRI scans are objective methods of measuring brain activity.
    • Case studies (Charles Whitman, Phineas Gage) support the link between brain damage and behavioral changes.
  • Weaknesses
    • Reductionist: Ignores social, environmental, and psychological factors.
    • Animal studies: Findings may not generalize to humans.
    • Correlational: Ethical constraints limit experimental research, making it difficult to establish causation.
    • Brain scanning technology: Low ecological validity
    • Counterargument: Drugs that increase serotonin activity (e.g. paroxetine) resulted in participants giving fewer and less intense shocks to others (Berman, 2009).