Welcome to the Prescribed Studies of Biological Psychology!
In this chapter, we dive into the "real-life" evidence that supports the biological theories you have been learning about. Think of this as the "detective work" of psychology. We will look at how scientists use brain scans, twin studies, and animal research to figure out why humans behave the way they do—especially when it comes to aggression and addiction.
Note: To understand how these studies work, you might want to cross-reference our chapter on "Research methods: correlations, brain-scanning and twin studies" for a refresher on the technology used!
The Classic Study: Raine et al. (1997)
Title: Brain abnormalities in murderers indicated by positron emission tomography (PET).
What was the aim?
Adrian Raine and his colleagues wanted to see if murderers who pleaded Not Guilty by Reason of Insanity (NGRI) had different brain activity compared to a control group of non-murderers. Specifically, they were looking for dysfunction in areas like the prefrontal cortex, which helps control impulsive behavior.
Who was studied? (The Sample)
The study used 41 murderers (39 males, 2 females) who had all been charged with murder or manslaughter but pleaded NGRI. They were compared to a control group of 41 people who were matched for age and gender. Six of the murderers had schizophrenia, so Raine ensured six people in the control group also had schizophrenia to make it a fair test!
What did they do? (The Procedure)
1. Each participant was injected with a radioactive tracer (fluorodeoxyglucose, or FDG). This tracer highlights which parts of the brain are active.
2. Participants then spent 32 minutes doing a "Continuous Performance Task" (CPT), which involved spotting signals on a screen. This kept their brains active during the scan.
3. A PET scan was then taken to see where the brain was using the most energy.
What did they find?
The results showed significant differences in the brains of the NGRI group:
- Lower activity in the prefrontal cortex (the brain's "brakes" that stop us from acting on angry impulses).
- Lower activity in the corpus callosum (the bridge between the two sides of the brain).
- Asymmetrical activity in the amygdala (the area linked to emotion and fear)—there was lower activity in the left side and higher in the right side compared to controls.
Key Takeaway and Conclusion
Raine concluded that brain structure and functioning are linked to violence. However, he was very careful to say that biology is not destiny. Just because someone has these brain patterns doesn't mean they are "born to kill"—it just might make them more vulnerable to acting aggressively.
Quick Review Tip: Remember the "BRAIN" acronym for Raine:
B - Biological abnormalities
R - Raine et al.
A - Amygdala/Asymmetry
I - Insanity (NGRI plea)
N - Nature (Biological causes)
The Contemporary Studies: Choosing Your Focus
For your exam, you usually focus on one contemporary study. Here is a breakdown of the three options listed in the syllabus.
1. Brendgen et al. (2005): The Twin Study
Focus: Are we born aggressive, or do we learn it? (Nature vs. Nurture).
The Study: Researchers looked at 234 pairs of 6-year-old twins (some MZ/Identical and some DZ/Non-identical). They asked teachers and peers to rate the children on two types of aggression:
- Physical aggression: Hitting, biting, or kicking.
- Social aggression: Spreading rumors or excluding others.
Findings: Physical aggression seemed to be mostly genetic (nature), because identical twins were much more similar than non-identical twins. However, social aggression was mostly environmental (nurture).
2. Li et al. (2013): Heroin and the Brain
Focus: How drug addiction changes brain function.
The Study: They used fMRI scans to look at the brains of chronic heroin users while they were at rest and when they were shown "drug cues" (images related to heroin use).
Findings: They found abnormal functioning in the posterior cingulate cortex (PCC). The more years a person had used heroin, the more abnormal the activity in this brain area was. This helps explain why it is so hard for addicts to resist cravings—their brain processing has actually changed.
3. Van den Oever et al. (2008): The Rat Study
Focus: Relapse and brain plasticity.
The Study: This study used rats to investigate why environmental "cues" (like seeing a place where you used to take drugs) cause relapse. They focused on AMPA receptors in the prefrontal cortex.
Findings: They discovered that when rats were re-exposed to drug-related cues after a period of abstinence, their brain chemistry changed rapidly. This "plasticity" (the brain's ability to change) in the prefrontal cortex is a key reason why cues trigger drug-seeking behavior.
Evaluating the Studies (The "GRAVE" Approach)
To get top marks, you need to evaluate these studies. Use the GRAVE acronym to help you remember what to check:
Generalisability: Can we apply these findings to everyone?
Example: Raine’s study only used people who pleaded NGRI. Can we apply this to "normal" impulsive murderers? Probably not.
Reliability: Was the procedure consistent?
Example: Both Raine and Li used brain scans (PET/fMRI). These are highly scientific and objective, meaning another scientist could run the same test and get the same result. This makes them highly reliable.
Application: How can we use this in the real world?
Example: If we know that social aggression is environmental (Brendgen), schools can create programs to discourage bullying. If we know brain chemistry causes relapse (Van den Oever), we can develop medicines to help addicts.
Validity: Does the study measure what it claims to measure?
Example: Doing a CPT task in a PET scanner (Raine) is quite artificial. It’s not the same as being in a real-life situation where you might feel angry. This means it might lack ecological validity.
Ethics: Was the study fair to the participants?
Example: In Raine’s study, the murderers might not have been in a fit mental state to give "informed consent." Also, the injection of a radioactive tracer is an invasive procedure.
Common Mistakes to Avoid
- Confusing the scans: Remember, Raine used PET (radioactive tracer), while Li used fMRI (magnetic/blood flow).
- Overstating the results: Never say "Raine proved that a bad brain makes you a murderer." Instead, say "Raine found a correlation between brain dysfunction and aggression."
- Mixing up Twin Types: MZ = Monozygotic (100% same genes). DZ = Dizygotic (50% same genes). If MZ twins are more similar than DZ twins, it suggests behavior is genetic.
Quick Summary Checklist
1. Can you describe the aim, procedure, and findings of Raine et al. (1997)?
2. Can you explain the difference between social and physical aggression in Brendgen’s study?
3. Can you use GRAVE to evaluate at least two of these studies?
4. Do you know which brain areas were highlighted (e.g., Prefrontal Cortex, Amygdala, PCC)?
Don't worry if the brain anatomy seems a bit confusing at first! Focus on the main idea: Biological psychologists use scientific tools to show that our "insides" (brain and genes) have a huge impact on our "outsides" (behavior).