Welcome to the Prescribed Studies for Biological Psychology!

In this chapter, we are going to look at the "real-life" evidence that supports the theories you have learned in Unit 2, Topic C. In Psychology, we don't just guess why people act the way they do; we use scientific research to find out. We will explore three main areas: how brain structure relates to murder, whether aggression is in our genes or our environment, and how specific genes or sleep patterns affect our behavior.

Note: To get the most out of these notes, you might want to quickly review the chapters on Brain Structure and Genes to remind yourself what the Prefrontal Cortex or the MAOA gene are!

1. The Classic Study: Raine et al. (1997)

Full Title: Brain abnormalities in murderers indicated by positron emission tomography (PET).

What was the aim?

Adrian Raine and his team wanted to find out if murderers who pleaded Not Guilty by Reason of Insanity (NGRI) had different brain activity compared to people who were not murderers. They specifically looked at areas like the prefrontal cortex and the limbic system, which we think are linked to aggression.

How did they do it?

The researchers used a sample of 41 murderers (39 men and 2 women) and a control group of 41 non-murderers, matched for age and gender. Participants were injected with a radioactive tracer and asked to perform a continuous performance task (CPT) for 32 minutes while a PET scan recorded their brain activity.

What did they find?

The murderers showed lower activity in several key areas compared to the control group:

  • Prefrontal Cortex: This area helps us control our impulses. Lower activity here might mean it's harder to stop an aggressive urge.
  • Corpus Callosum: The "bridge" between the two brain hemispheres. Reduced activity here might suggest poor communication between the logical and emotional sides of the brain.
  • The Limbic System (Amygdala and Hippocampus): Lower activity was found in the left side of these areas. This system handles our emotions and learning.

Key Takeaway

Raine concluded that localized brain damage could make someone more likely to commit violent acts. However, he warned that biology is not destiny—social and environmental factors still matter!

Quick Review: Evaluation of Raine
  • Strength: High control. By matching the murderers with a control group of the same age and gender, Raine made the comparison much fairer.
  • Weakness: The PET scan used in 1997 provides a "snapshot" of the brain, which can sometimes be a bit blurry or lack detail compared to modern scans.
  • Weakness: We cannot say the brain abnormalities caused the murder. It is possible that the lifestyle of the murderers caused the brain changes, rather than the other way around.

2. The Contemporary Study: Brendgen et al. (2005)

Full Title: Examining genetic and environmental effects on social aggression: A study of 6-year-old twins.

What was the aim?

Brendgen wanted to see if two different types of aggression—physical aggression (hitting) and social aggression (gossiping/excluding others)—were caused by genes or the environment.

How did they do it?

The researchers studied 234 pairs of 6-year-old twins from Montreal, Canada. They compared Monozygotic (MZ) twins, who share \(100\%\) of their genes, and Dizygotic (DZ) twins, who share about \(50\%\). They collected data using teacher ratings and peer ratings (asking classmates who they thought was most aggressive).

What did they find?

  • Physical Aggression: There was a much higher correlation between MZ twins than DZ twins. This suggests that physical aggression is mostly influenced by genes (nature).
  • Social Aggression: The correlations were similar for both MZ and DZ twins. This suggests that social aggression is mostly influenced by the environment (nurture), like how parents or friends behave.
  • The Link: Children who were physically aggressive when they were younger were more likely to become socially aggressive as they grew up.

Key Takeaway

Physical aggression is "nature," but social aggression is "nurture." As kids get older, they might learn to "trade" their fists for mean words because social aggression is more acceptable in school.

Quick Review: Evaluation of Brendgen
  • Strength: Used triangulation. By getting data from both teachers and peers, the results are more reliable than just asking one person.
  • Weakness: The study only looked at 6-year-olds. We don't know if these findings would stay the same as the children hit puberty or become adults.

3. Contemporary Study Options (Choose One)

In your exam, you might need to discuss one of the following two studies. Here is a simplified version of both.

Option A: McDermott (2008)

Topic: The MAOA gene and provocation.

McDermott studied the MAOA gene (sometimes called the "warrior gene"). Participants played a computer game where they could "punish" an opponent who stole their money by making them eat hot sauce.
Finding: People with the low-activity MAOA gene were more aggressive, but only when they were highly provoked (when a lot of money was stolen). If there was no provocation, they weren't more aggressive than anyone else.
Lesson: Aggression is an interaction between our genes and our situation.

Option B: Hoefelmann et al. (2006)

Topic: Sleep behaviors in high school students.

This study looked at how circadian rhythms and sleep patterns affect behavior in teenagers.
Finding: They found significant links between how much sleep students got and their daily habits. For example, students who had poor sleep quality or short sleep duration were often less physically active and spent more time on screens.
Lesson: Our internal body clock and our lifestyle choices (like screen time) are closely linked to our overall health and behavior.


Common Student Mistakes to Avoid

  • Mixing up MZ and DZ twins: Remember, Monozygotic = Midentical (\(100\%\) same genes). Dizygotic = Different (\(50\%\) same genes, like regular siblings).
  • Ignoring the "Interaction": In McDermott's study, don't just say "the gene makes them aggressive." It only makes them aggressive when provoked.
  • Overstating Raine's findings: Raine did not say that brain scans can predict who will be a murderer. He only found a correlation (a link) in a specific group of people.

Summary Table for Revision

Raine (1997): Brain structure (PFC/Limbic) \(\rightarrow\) Violent behavior.
Brendgen (2005): Physical aggression = Genes; Social aggression = Environment.
McDermott (2008): Low MAOA gene + High provocation = More aggression.
Hoefelmann (2006): Poor sleep \(\rightarrow\) Linked to screen time and low activity.